Millipedes, Centipedes, Sowbugs, Mites, misc Archnides


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Category: 7A, 8

Millipedes, Centipedes

File:Female Illacme plenipes (MIL0020) with 618 legs - ZooKeys-241-077-SP-6-top.jpg

Millipede.  Image Courtesy Marek, P.; Shear, W.; Bond, J. (2012).  Creative Commons SA 3.0. It Has to be a Record -618 legs

Millipedes. Millipedes are elongated with 60 or more legs, with most body segments bearing 2 pair. Some of the larger species have as many as 400 legs. Their bodies can be either cylindrical or flat with short 7 segmented antennae.  One of the more spectacular species is a 12-inch African millipede that for years has been sold in pet shops in the United States. This practice was recently discontinued due to governmental regulations. The reason for this intervention in the importation of these creatures was not the millipedes but was due to a small mite that was frequently associated with them. These tiny arthropods or so called feeder mites function to clean the millipedes. It is quite interesting to watch these bigger millipedes move.  With almost 400 legs, they need a system to keep from tripping themselves. When a millipede “runs’, it lifts each pair of legs in sequence with a wave-like “progression moving down the body. haydeniana

Top Twelve-inch African Millipede. Image Dr. Kaae. Bottom Image Courtesy Walter Siegmund (talk) CC BY-SA 3.0.

The 12-inch African millipedes depicted above was imported from South Africa for years and sold in pet shops throughout much of the United States.  Several years ago importation of these beasts was prohibited via the USDA. Reportedly the concern wasn’t that these critters would get loose and become agricultural pests. However, the problem apparently was with small mites that were commonly associated with this millipedes-possible pest?  In actuality these mites are what are commonly termed feeder mites. They function to clean the millipedes. That was a little sad as the kids loved the millipedes and they were easy to keep and certainly cheap to feed.

If disturbed, millipedes will typically coil up with their head (most vulnerable part of the body) in the center. This of course protects the most vulnerable parts of their body. There are a group of millipedes called the pill-millipedes which roll up much like a pillbug or so called roly-poly. These occur in many tropical areas with a species from Africa reaching the size of a golf ball.   talakaveri.jpgMating

Top. A rolled up African Millipede. Image Dr. Kaae. Pill Millipede from Talalaveri Coorg, India. Image Courtesy L. Shyamal CC-BY 2.5.  Bottom. Millipede Love. Actually They are Mating. Image Courtesy Muhammad Mahdi Karim GNU Free Documentation `1.5.

Millipedes typically feed on decaying vegetation, but they occasionally become pests on plant parts with ground contact. Most millipedes in the continental United States rarely exceed 3 to 4 inches in length. However, some of the tropical species can reach 1 foot. Sometimes millipedes accompanied by centipedes and sowbugs migrate in great numbers. This is believed to be the result of a heavy population build-up because of extremely favorable environmental conditions followed by drought or some other unfavorable conditions such as removal of breeding sites.  Migrations at times have been so heavy as to make it necessary to sprinkle sand on slippery railroad tracks to provide traction for the driving wheels of the trains.  In one reported migration, a farmer shoveled several gallons of these critters a day from his front porch for three weeks.

These animals are relatively harmless to humans and do not bite. However, a few species can defend themselves by ejecting irritating fluids a distance of several inches. A Haitian species is reported to discharge its secretion at distances close to a yard. The fluid is irritating and possibly dangerous to the eyes and reportedly is responsible for occasional blindness in chickens and other animals. One of the irritating fluids in some millipedes is hydrogen cyanide, the same chemical once used in the gas chamber. Small amounts are released, and the estimated total is approximately 1% the amount needed to kill a human and 40 % the amount needed to kill a small bird.

Closer  to home, an insect dealer at one of our Cal Poly insect Fairs was recently observing a small tropical millipede when it shot a spray of some unknown chemical from a distance of over 2 feet directly into his eye. The results were quite painful and resulted in considerable swelling.

Swollen and Inflamed Eye due to Contact with Millipede Defensive Chemical. Image Dr. Kaae

Millipedes grow slowly and some can live for several years. Most species prefer damp habitats and remain hidden during the day under objects. Moisture control is of extreme importance in the control of millipedes.

File:The strangest millipede ever ... (8053641856).jpgOctoglena sierraDefensive coil 

The Cool Thing about Millipedes Is that They Come in All Colors, Sizes and Shapes. Top Image Courtesy of Gilles San Martin from Namur Belgin CC BY SA 2.0.  Left Image Courtesy Marshal Hedin CC BY-SA 2.0. Right Image Courtesy Vanden Spiegel D. Golovatch S Gilles San Marten CC BY-SA 3.0.

Centipedes. Centipedes are elongated, flattened, worm-like animals with 15 or more pair of legs, with each body segment bearing a single pair. The last pair is usually longer and points directly backwards and look very similar to its elongated antennae. As a result, the head end of many centipedes looks very similar to the tail end. This is advantageous, since a potential predator may grab the wrong end which could result in a painful and potentially fatal mistake-good reason to be left alone! The first pair of legs is modified into a pair of fang-like poison jaws, which are capable of inflicting a painful bite. Smaller centipedes are considered harmless to humans, but the bites from larger species can be quite painful, resulting in local swelling. This can debilitate an adult human for a few days. Some of the tropical species are quite large and are greatly feared by humans.

One of the most well-known of these critters is a giant that lives in caves in South America and can reach a length of 18 inches.  This powerful beast hunts mice, bats and other relatively large critters.  Once seized with its venomous poison jaws, captured bats are said to die in as little as 30 seconds. Although probably not capable of killing a human, villagers in Venezuela claim that the bite of one of these giants did kill a child.  I do know of an individual that was" playing" with one of these creatures (not smart) and was bitten.  He was sick for a few days with a severely swollen hand.

At times, it almost appears that these and other arthropods have the ability to think. Of course this is quite doubtful, but they have been well-equipped to react instinctively (almost appearing intelligently) too many circumstances.  We recently watched a large Vietnamese centipede catch and feed on a cricket.  Once caught, the centipede immediately cut off the cricket’s legs, thus removing its ability to escape. Thinking that this was an accident, we fed it another cricket with the same results. Taking this impromptu experiment a step further, we fed a cricket to a different centipede with the same result-thought the first one might have been smarter-oops!  They don't think.

Giant South American Centipede.  Image Courtesy Katka Nemčoková CC BY-SA 3.0

Underside of Large Vietnamese Centipede Head Showing Poison Jaws. Image Dr. Kaae.

The authors recently documented a case of a bite from a large species of Arizona centipede. In this situation, a homeowner bent over to drink from a water hose. Unfortunately, a 12-inch centipede had recently occupied the hose, and when the water was turned on, the centipede appeared and bit the individual on the tongue. His tongue and mouth swelled considerably and he was in pain for several days.

These organisms are nocturnal and remain hidden during the day in protected locations such as under loose bark, rotting logs, rocks and in tunnels and voids in the soil.  Centipedes are fast moving, and most are predaceous on spiders, insects and other small animals. The diet of the larger species is not limited to insects or other arthropods. They certainly are large and strong enough to subdue small snakes, mice, lizards and even birds. They can easily be distinguished from millipedes by how quickly they move. Because millipedes feed on plant tissue, there is no need for agility and they move quite slowly. You don’t need to be fast to run down a leaf. Generally, plant-feeding arthropods are slow while predators are relatively fast moving.

The common house centipede is about 1-inch long, grayish-tan in color with long antennae and extremely long legs. As their name implies, these creatures are commonly found running over walls and ceilings in homes. They are harmless and could be considered beneficial, as they feed on cockroaches, houseflies, moths, spiders and other pests found in and around the home. However, I am sure most homeowners would not consider them an added benefit to the home, especially the Thai species shown below.

Top. Common U.S. House Centipede. Image Dr. Kaae. Bottom. Thai House Centipede-Image Courtesy John Moore.

With the exception of the common house centipede, these creatures are not as commonly found in the home as millipedes.  Of course part of the reason for this is that their outdoor populations never reach that of millipedes.  However, if a centipede does occur indoors, it can be somewhat stressful.  One evening (on a Hawaiian trip) one of our visitors was washing dishes and a 7-inch centipede appeared from under the dishwashers (apparently a fairly common occurrence in Hawaii).  She came running from the kitchen screaming centipede, centipede!  According to her, she couldn’t sleep that night. A note of importance-never try to transport living centipedes on a commercial airline. After capturing the centipede, I decided it would make a nice addition to our insect zoo at Cal Poly.  I neatly packed it away in a small container in my luggage.  Of course on getting home, the critter was dead.  I guess it gets pretty cold in the cargo area of planes.

On a later occasion, I decided to bring back several giant millipedes (12-inch beauties) I had collected in Malaysia.  Keeping in mind that they wouldn’t make it in the cargo area, I decided to carry them in my carry-on luggage.  While waiting for the plane to begin loading, I decided to check and see how they were doing—big mistake!  One of the stewardesses saw them out of the corner of her eye and freaked.  She first thought they were snakes and called security.  After convincing all involved that they weren’t snakes, I still couldn’t convince anyone that they were harmless.  I was subsequently escorted from the airport to release the monsters back into nature-almost missed that flight.  I guess it could have been worse.  Luckily for us, the movie “Snakes on a Plane” had not yet been released.

Not learning from those experiences, I later transported a large variety of living critters (scorpions, walking sticks, millipedes, tarantulas, etc.) on Alaskan Airlines up to Oregon for a presentation. I was going to a presentation at the Oregon Pest Control Association. I had no problem getting them on the plane on the way up but was stopped by security on the way back. Major alert-you would have thought I was some kind of terrorist.  After convincing the authorities that these critters were not going to kill anyone, and that I wasn’t totally nuts, the additional problem was that it was prohibitive to bring living animals of any kind on a plane. I think the exceptions were dogs and cats in cargo and goldfish. They again wanted me to take the specimens out of the airport and release them.  After some fast taking and actually doing a short presentation on these arthropods to the airline officials, they let me put them in cargo after they triple boxed them. Again, we almost missed that flight as well.

By the way, when I got to the Pest Control Association and asked what time was my hour presentation, their answer was I was supposed to talk the whole day--6 hours to 300 people. After a few minutes of panic, I decided to cover a good deal of the material in this class-already knew most of it. They seemed to love it.

We once stopped at a roadside stand in Thailand to buy some dried-roasted caterpillars for an afternoon snack (when in Rome do as the Thai-or something like that)) and were offered a quart bottle of home-brewed whiskey. However, instead of having a worm in the bottle as doe’s Mexican tequila, there was a 14-inch pickled centipede. Drinking the whiskey enhanced by centipede was said to give the consumer great strength or at least make the consumer think he or she had great strength until they sobered up. This belief is apparently common in several of the South-East Asian countries. By the way, the worm in the bottom of the tequila bottle is a caterpillar that feeds on the century plant from which tequila is derived.

As you might expect, these arthropods as a source of human food in some countries (mm-centipedes on a stick!)

Centipedes on a Stick. Image Courtesy Denise Chan from Hong Kong, China CC BY-SA 2.0

Crustaceans. This is a very large group of arthropods that occupy diverse habitats, but the majority occurs in fresh and salt water. The more familiar forms (and better tasting) include the crabs, lobsters and shrimp. While these forms are beyond the scope of this text, there are a few common terrestrial crustaceans that we encounter in our daily life--the sowbugs and pillbugs. Both were introduced from Europe and are now distributed throughout the United States and are two of the common larger backyard arthropods. Although these critters have several minor structural differences, one easy way to distinguish one from the other is that pillbugs, as their name implies, are capable of rolling up into a tight pill-shaped ball and the sowbugs are not. Both types possess 7-pair of legs and have a fairly short life cycle consisting of 2 or 3 generations per year. Each female has approximately 50 young which can be found on the underside of the female.

Sowbugs (larger specimens) and Pillbugs. Image Dr. Kaae.

Being crustaceans, sowbugs and pillbugs are not well adapted for a terrestrial way of life. Unlike insects, they lack a waxy layer on the outside of their exoskeleton; this functions to reduce water evaporation from the body. Similarly, the external openings of their breathing system are not fitted with valve-like structures (spiracles in insects) which can be used to close off the system when not in use. This lack of spiracles results in an additional source of water loss from the inside of their body.  Dehydration or the loss of water from an arthropod's body is a continuous problem. Because these creatures are relatively small, they have a rather large surface-area-to-body volume ratio (e.g., large area to lose water from and relatively small area to store it internally). In order to prevent dehydration, sowbugs and pillbugs remain hidden during the day in moist situations such as leaf litter, under rocks and logs and forage for food at night. It is common to find large numbers huddled together in order to reduce their surface area and thus conserve moisture.

Moisture control is of extreme importance in controlling sowgus, pillbuigs, millipedes and centipedes

Sowbugs and pillbugs chiefly feed on decaying organic matter such as rotting leaves and twigs, dead animals and even feces. On occasion, they cause minor damage to plant roots, seedlings and ripe fruit in contact with the ground. In cases where they become pests, their presence can be reduced by removing breeding and hiding sites.

Interestingly enough there is a video of an individual holding 2 giant Crustaceans that belong to the same group as the sowbugs and pillbugs (namely Isopods). It is actually amazing that sowbugs and pillbugs are quite similar to and are related to these “giant” Isopods”, especially considering where both are typically found and the extremely difference in size. The giant isopod can grow to a length of over 16 inches, which makes it one of the largest members of the crustacean family. Like its terrestrial cousin the pillbug, the giant isopod's body is protected by a hard shell that is divided into segments

File:Bathynomus giganteus.jpg ac Deep sea creatures (7472073020).jpg

Giant Isopods-Close Relatives to Sowbugs. Images Courtesy of from Left Friend of Borgx CC BY-SA 3.0. Right NOAA-Public Domain and Bottom Laika ac CC BY SA 3.0

These giants are of minor interest to commercial fisheries because they are caught and scavenged beyond marketability before they are recovered. The few specimens caught in the Americas and Japan with baited traps are sometimes seen in public aquariums.

These creatures are a good example of deep-sea gigantism (like giant squid). Sowbugs and pillbugs and other "typical" isopods are less than an inch in length. Adults of “supergiant" species are boviously much larger and heavier. Like some pillbugs, they also possess the ability to curl up into a "ball" where only the tough shell is exposed. This provides protection from predators trying to strike at the more vulnerable underside and the head. Their large eyes are compound with nearly 4,000 facets and spaced far apart on the head. As with sowbugs, they bear 2 pairs of antennae and 7 pairs of legs.

 Questions - True/False 

1.  Moisture control is of extreme importance in the control of millipedes, centipedes and pillbugs. These arthropods normally live in moist conditions.

2. Sowbugs and pillbugs are crustaceans and lack the waxy layer around their body, thus are more susceptible to water loss than insects. 

3. An easy behavioral mean of distinguishing millipedes from centipedes is speed of movement. Millipes are fast moving and centipedes are relatively slower moving.

4. Millipedes feed on mainly ov decaying vegetation or fruit in contact with the ground.

Scorpions, Vinegaroons and Harvestmen

The arachnids are the largest class of animals (exclusive of the insects), with 65,000 known species worldwide, and undoubtedly there are another million or so yet detected species. Its members exist nearly everywhere—often in considerable numbers. Most authorities recognize 11 orders with some being relatively rare. This text will discuss several of these orders. Arachnids can be distinguished from other arthropods by a fused head and thorax (cephalothorax); they also have an abdomen and 4 pairs of legs. The first pair of appendages behind the mouth is the chelicerae (chelicera-singular), and the second pair is the pedipalps. The chelicerae and pedipalps vary considerably in structure and function in the different orders of this class. These differences are used to distinguish one order from another.

 Fang-like Chelicerae of a Tarantula and Short leg-like Pedipalps (immediately left of fang). Image Dr. Kaae.

Scorpions. Scorpions have been found in many fossil records, including marine Silurian and estuarine Devonian deposits, coal deposits from the Carboniferous Period and in amber. The oldest known scorpions lived around 430 million years ago in the Silurian period. Though once believed to have lived on the bottom of shallow tropical seas, early scorpions are now believed to have been terrestrial and to have washed into marine settings together with plant matter. These first scorpions were believed to have had gills instead of the present forms' book lungs though this has subsequently been refuted. The oldest Gondwanan scorpion (Gondwanascorpio) is considered the earliest known terrestrial animals from Gondwana. The eurypterids, marine creatures that lived during the Paleozoic era, share several physical traits with scorpions and may be closely related to them. Various species of Eurypterida could grow to be anywhere from 3.9 inches to 8.2 feet in length.

Scorpions are well-known Arthropods that range in distribution as far north as Canada and to as far south as the southern tip of South America. These creatures are hardy and can survive in extreme conditions including temperatures as high as 115 F, being frozen solid for weeks, total submersion in water for up to 48 hours, irradiation levels many times the lethal limit to humans and lack of food for up to 1 year. These are among the oldest ancestral arthropods having crawled from the oceans for a terrestrial way of life over 350 million years ago. Because scorpions are greatly feared by many humans, one can only imagine if these, ancestral monsters existed today. Imagine the extreme reaction to encountering one of these several foot long scorpions! Their chelicerae are used to cut and chew food while the pedipalps are pincher-like, or chelate, and are used to subdue and hold their prey during feeding.

California Desert Scorpion with Pincher-like (chelate) Pedipalps. Note the Small Jaw-like Chelicerae Located in the Front of the Cephalothorax. Image Dr Kaae.

The cephalothorax bears 1 pair of simple eyes located dorsally near the mid-line of the cephalothorax and several along the lateral margins on each side thus allowing a scorpion to see in all directions at any one time. These eyes are comparatively simple and do not produce precise images.  However, they are quite sensitive to minor differences in brightness (dark versus light and shades) and therefore movements. As a result, it is very difficult to approach a scorpion without being detected. As with us, their eyes can be dazzled or even harmed by bright sunlight. Scorpions use the same tool we use to prevent this from occurring, namely sunglasses if you will (amazing stuff). Scorpion eyes contain pigments that migrate toward the surface when exposed to bright light (sunlight) which of course form a protective barrier. As light dims, the pigments merely drain to the lower areas of the eye.

The abdomen terminates in a 5-segmented tail-like structure bearing a bulbous stinger at the tip.The tip of the stinger is very sharp and quite strong with one 1/4 of its composition consisting of zinc, iron and manganese. Males can be distinguished from females by their larger pair of comb-like structures (pectins) which are located on the underside of the cephalothorax. The function of pectins is unknown, but is thought to be used both for detecting food and the presence of the opposite sex.

File:Scorpion Photograph By Shantanu Kuveskar.jpg

Top.  Five Segment Tail with Sharp Bulbous Sting.  Also Note Fine Receptive Hairs (also called setae) on Various Parts of Body. Image Courtesy of Shantanu Kuveskar  CC BY- SA 4.0.  Botttom. Comb-like Pectins on Underside of Scorpion.  Image Dr. Kaae     

These creatures have a unique method of locating their prey which consists of any living animal their size or smaller. These include insects, other scorpions and arachnids, birds and small mammals. Scorpions are nocturnal and lack well-developed eyes. Vision is of little use for this purpose. Instead, their legs are equipped with many fine erect hairs that are extremely sensitive to the movement of an approaching prey. When a beetle or any other prey approaches a scorpion, its movement creates 2 types of waves across the ground.  One type is fast moving and the other is slow. A hungry scorpion stands with its legs spread in an almost circular configuration. As a result, their legs essentially point in all possible directions. They can easily detect the direction of a potential prey by detecting which leg is disturbed first by the fast moving wave pulses. Apparently the distance away from the prey can be computed by the scorpion by using the difference in time it takes the fast moving waves and slow moving waves to reach the scorpion's leg. The authors have no idea how a scorpion uses wave mechanics or the laws of physics to find their prey.

When scorpions are viewed under ultraviolet light (e.g. blacklight), they glow.  This is due to structures in their exoskeleton that reflect ultraviolet light. The exact reason for this phenomenon is not known. However, we also do not know exactly how or what scorpions see at night. It would make perfect biological sense that scorpions might be able to see ultraviolet wave light and thus another possible means of finding a mate in the dark.  Also many plants emit or reflect ultraviolet light to attract insect pollinator (e.g. bees, moths, flies and beetles).  Many insects are attracted to ultraviolet light.  This is well illustrated by the fact that entomologists use ultraviolet lights to attract insects when night collecting.  Of course all this adds up to the distinct probability that scorpions reflect ultra-violet light in order to attract these types of insects.

Scorpion Viewed Under Ultraviolet Light. Image Courtesy Jonbeebe at English Wikipedia CC BY 3.0

As with many arthropods, scorpions exhibit external reproduction. When a female is ready to mate, she will deposit a sex pheromone (spermatophore) on the ground. She typically doesn't move far from this location. Any sexually mature male of the same species that randomly encounters this chemical attractant can detect its present by sensory (olfactory) receptors located on the previously described pectins. As a result, the male instinctively is aware that a female is nearby and that she is ready to mate. Actually scorpions and other arthropods are not really aware of anything but are programmed to react to given stimuli.  Once the male perceives this chemical, his mating reaction is activated. At this point, he exhibits a rather violent series of jerky movements-named juddering. As a result of this lurching, seismic waves are sent across the ground thus attracting the female. Mating can get a little rough at this point. It is not uncommon for the male or female or both to club (not sting) each other with their tail (stinger). The male in some species will actually sting the female in the soft joint between the opposing claws of her pinchers. This obviously does not kill the female but apparently tends to tranquilize her to point where she is less combative and more receptive to mate. It is well documented that scorpions are relatively immune to the venom of their species. Mating terminates in his grasping her pedipalps and dragging his mate over the stalked spermatophore.

Once mated, it generally takes a year before the female gives live birth to a dozen or more young. Typically the young scorpions crawl up on the back of the female until their first molt. If the young scorpions is moved from the mother’s back prior to their first molt, they will typically die due to the lack of sufficient moisture. The mother secretes a liquid that prevents this dehydration. It is not uncommon to purchase an already mated female scorpion from a pet shop. In captivity, an ill-fed or stressed female will often eat her newborn young. Even if they survive birth and the jaws of their mother, young captive scorpions rarely survive to adulthood because of their precise humidity requirement during molting.

Female Scorpion with Newly Born Young on Abdomen-Yum, Yum!  Public Domain.

It has been postulated that the sex pheromone of some scorpions is not only used to find a potential mate, but it is occasionally used to attract dinner. Apparently some larger species of scorpions will duplicate the sex pheromone of different smaller species. When males of the smaller species begin juddering, the larger scorpion quickly finds and consumes the one-course meal (fresh scorpion!).

The sting of scorpions is used to immobilize prey and occasionally for defense. The effect of a sting on humans depends primarily on the species of scorpion involved. Typical symptoms vary tremendously ranging to a very mild tingling to some pain and swelling to possible death. Worldwide, almost all scorpion species are not considered dangerous to humans. Of the more or less 1500 worldwide species, only a comparatively few are considered potentially dangerous to humans. The venom of the most toxic species of scorpions is reportedly 100,000 times more toxic than cyanide.  Fortunately little is normally injected. In the United States, the sting of only 2 in the genus Centruroides can be considered dangerous and rarely result in human death.  These occur across much of the Southern United States down into Mexico. In Arizona, the bark scorpion in the genus Centruroides is a dangerous species accounting for 75 human deaths from 1926 to 1996 and on a yearly basis far fewer since then.  Most of these casualties occur in children and babies.  This is undoubtedly due to more venom per body weight. There are twice as many deaths from scorpion stings than from the bites or stings of all other U.S. forms of venomous animals (except the honeybee) combined; this includes poisonous snakes. Actually the honeybee causes far more deaths.  One might think the Africanized bee might add significantly to this figure.  However, the regular honeybee is the main culprit.  It is a matter of more exposure to bees than other arthropods and the fact that some individuals are allergic to the sting of  honeybees.  In addition almost everybody has been stung by a bee at one time or another. How many people do you know that has been stung by a scorpion?

Centruroides scorpions have long and narrow pincers and tails and are yellow-reddish in color with 2 dark stripes running down the back.  The venom is neurotoxic and consequently affects nerve transmission. The Durango scorpion (Centruroides)) is found in Durango, Mexico.  Death from the sting of this species can occur in as little 3 hours. If stung, the site should be iced immediately. This should slow or prevent spread of the venom. A physician should be consulted immediately. An effective antivenin is available and if quickly applied death can easily be avoided.  The sting of this scorpion will rarely kill an adult unless some type of allergic exists. On the other hand, stings to small children or babies can be extremely dangerous.

In Mexico, many deaths occur per year from the sting of this genus. This is due to the lack of adequate medical facilities and the openness of many of the houses. In northern Mexico, many of the houses are poorly constructed and lack window glass. These scorpions are climbers and can be found in the walls and ceilings. Homes with thatched roofs are attractive habitats and commonly harbor dozens of scorpions. This type of roof construction is prevalent throughout parts of Mexico. The main victims are babies and young children under 2 years of age. If a young child accidentally rolls over on one of these scorpions in bed, the parents frequently are not aware of the sting until it is too late.


Centruroides scorpion. Courtesy Charles & Clint - Flickr. CC BY_SA 2.0

Although there are no dangerous species native to California, the Centruroides scorpion has been found here in a few isolated instances. A number of years ago, a species of this genus was found infesting several blocks in Anaheim Hills. Apparently, a pregnant female was accidentally introduced into a recreational vehicle that had been stored for several months along the Arizona side of the Colorado River. This population was eradicated by Orange County Vector Control.

Several species of scorpions are commonly available in pet stores. These include the emperor and imperial scorpions--the former being most commonly sold. The black emperor scorpion is an African species and is the largest species in the world (up to 10 inches or more total length). It is characterized by very large, roughly textured pedipalps. The imperial scorpion occurs in SE Asia and is more aggressive than the emperor.  Recently, importation of the emperor scorpion has been curtailed in California.

African Emperor Scorpion with Large Rough Pedipalps. Image Dr. Kaae.

This docile species rarely stings and is somewhat reluctant to pinch with its pedipalps. One symptom of a sting is typically a mild, short-lived burning sensation. This symptom is typical very mild because this scorpion is slow moving and does not whip its stinger. A sting form this species normally results in a shallow pin prick with very little toxin injected before the victim withdraws that part of the body being attacked. However, after handling hundreds of these scorpions with no sting, I recently received a rather deep penetrating sting (careless handling). The result was a painful burning sensation (worse than a bee sting) that lasted for 2 days. The difference in my reaction to both types of stings may be due to the fact that adult scorpions frequently do not inject their venom with all stings. 

Even though it is very difficult to receive a painful sting from the emperor scorpion, it is unwise to allow the uninformed to handle any scorpion. The human mind is unpredictable and fear can result in real symptoms that are not the result of the scorpion's toxin (e.g. psychosomatic symptoms). The authors recently observed such a reaction at a county fair. A graduate entomology student was handling an emperor scorpion and received a rather minor sting, the type that should result in nothing more than a mild tingling. It became immediately apparent that he was not familiar with the relatively harmless effect of such a sting and panicked. He immediately wrapped a T-shirt around his arm forming a tight tourniquet in attempt to shut off most of the blood flow to his wounded hand. He requested medical attention resulting in fair officials sending for paramedics. He reported pounding of his heart and feeling faint. Being concerned about the possibility of his going into shock prior to the arrival of an ambulance, I decided to try to calm him down. After a short discussion about the nontoxic nature of this scorpion's sting, I allowed the scorpion to sting me several times with no obvious symptoms. I am sure he thought I was crazy but this seemed to give him some relief and by the time the ambulance arrived he was back to normal. Clipping off the very tip of a stinger can eliminate the possibility of being stung by a pet scorpion. This does not hurt the animal and prevents its ability to penetrate the skin.

Warning-Do not let scorpions sting you on purpose—like many other entomologists, I am a little nuts!

Pet scorpions may be kept in small aquariums on a variety of substrates; however, sand is not desirable. Sand is abrasive (sand paper!) and can wear of the waxy outer layer of an arthropod’s exoskeleton-thus causing an increased loss of water from the body and possible death. A water source is necessary, and weekly feedings of a cricket or 2 will insure survival. Most species takes several years to reach adulthood and generally live a year as an adult. Because scorpions sold in pet stores are collected as adults, they generally live less than a year in captivity. Emperor scorpions are quite different than almost all other species, and more than one can be kept in the same cage.

The Imperial scorpion is an Asian species that is also black, smaller than the emperor and has smoother, smaller pedipalps. Imperial scorpions are more aggressive than emperors but still are reluctant to sting; they will pinch when agitated. Generally, scorpions with large pedipalps do not rely on their sting to immobilize prey.  As a result, their venom is not generally very toxic. I had always thought scorpions fed almost exclusively on other arthropods, but one day in Thailand I saw a small chick  being dragged down into a wood-pile. On close inspection, an imperial scorpion had it by the leg and was going to have Colonel Sanders for lunch.

Scorpions and other arthropods are a source of human food in many areas of the world. A friend of ours was conducting a business transaction in a village in northern China. The transaction was going to bring considerable wealth to the village and a feast was prepared in his honor. The main dish was boiled scorpion served in the center of a wooden platter rimmed with bee larvae and fried cicada nymphs.

Scorpion on a Stick. Yum Yum. Image Courtesy istolethetv CC BY SA 2.0 International

Scorpions and Modern Medicine. Scorpion venom is possibly finding some use in modern medicine. The venom of the dangerous death stalker scorpion acts like a smart bomb that seeks out cancer cells.  In laboratory tests scorpion venom, armed with radiation or anticancer drugs may kill cancer cells one at a time, preserving the rest of the healthy tissues.

Scientists at University of California, Irvine (UCI) have isolated and synthesized a chemical (name: TRAM) in this arachnid’s venom that eventually could become a drug to treat autoimmune diseases -- disorders in which the immune system attacks itself.  It has great potential for the treatment of rheumatoid arthritis, multiple sclerosis and lupus. In principle, it should also work on about 60 other autoimmune disorders, but that won’t be known without extensive testing. The compound also holds promise for organ transplant patients, whose immune systems must be prevented from rejecting the new body part. During tests, the UCI researchers found the compound suppresses the immune system's T-cells, which trigger any fight against invaders. (The T-cells are the same cells the AIDS virus destroys.) Like scorpion venom the synthetic compound blocks a cell membrane channel called IKCa1.

Whipscorpions-Vinegaroons. The whipscorpions are mainly tropical and live in the Southern United States. They are less common in California but prevalent from Arizona to Texas. In California, they commonly occur along the California-Arizona border. The chelicerae are opposing and jaw-like, and the pedipalps are weakly chelate (pincher-like) but quite powerful. The body is elongated, slightly flattened and characteristically bears an elongate whip-like tail. These arachnids are also called vinegaroons, as they readily squirt vinegar (a defensive secretion), or acetic acid from their tails if disturbed. A common misconception is that the bite from a vinegaroon will result in a vinegar taste in your mouth. They are easily kept as pets and are handy since you can shake them over your dinner salad-a quick source of vinegar- if I haven’t told you yet, some entomologists are a little unusual-not me of course. I should also mention that my wife Pat does not belong to the former group. I guess she is unusual in that she likes bugs, especially spiders.

The secretion from the tail of the whipscorpion has a high content of acetic acid (the main component of vinegar) and low level of caprylic acid. The later reportedly functions to increase the defensive activity of acetic acid.  Acetic acid is water soluble and will “bead up” when on a waxy surface such as the exoskeleton of an arthropod prey. Since the most important predators of whiptailed scorpions are other arthropods, a secretion of acetic acid alone would likewise “bead up” on the exoskeleton thus reducing its effectiveness.  Apparently caprylic acid is more attractive to lipids and actually serves to spread both components over the prey’s body, and enhances penetration into the body.

Left. Image Dr. Kaae. Whiptailed Scorpion from Arizona, Mastigoproctus giganteus. Right. Same Species Carrying Egg Sac. Image Courtesy Acrocynus CC BY-SA 3.0

The whiptailed scorpion most often encountered in Arizona is Mastigoproctus giganteus, the largest species in the world.  It measures up to 3 inches in length not including the tail. These nocturnal animals hide in short burrows in the soil and feed on insects and small animals. Whiptails are long-lived (up to 12 years), harmless to humans and quite docile. They can be easily kept in an aquarium but require a water source and feeding about once every 2 weeks.

Sunspiders-Windscorpions. This is a moderately-sized group of arachnids with over 120 species in North America. In the United States, most species are found in the desert areas, but some can be found throughout the southern section of the western states. They are 1 to 2 inches long, usually pale in color, hairy and have a waist or constriction (petiole) connecting the  cephalothorax to the  abdomen. The chelicerae are characteristically very large and fang-like and can be as big as the cephalothorax. These arthropods are commonly mistaken for vinegaroons.

A Sunspider or Windscorpion from Southern California. Image Dr. Kaae

Although sunspiders can be quite aggressive, they lack venom and are not considered dangerous to humans. The pedipalps or second pair of appendages behind the mouth are leg-like, quite elongated and used as feelers. These nocturnal arachnids have been called by a variety of names including sunspiders, camelspiders, sunscorpions and windscorpions. The latter name refers to their ability to "run like the wind." As one might expect, they are predatory on a variety of smaller animals including lizards, mice and insects.

These arthropods are difficult to keep in captivity and typically die a few months after capture. A very large Egyptian species occasionally is available in pet shops. This species can live in captivity for several months. They require daily feeding and considerable space to move.

There are a number of camel spider stories that have recently spread on the internet. These began to appear during the 1990-91 Gulf War and have now reemerged and become even more widespread with the return of U.S. troops in Iraq. Almost everything on the web (emerging from Iraq) about the size, ferocity and danger of these arthropods is untrue. Some of the fallacies are listed below:

1. Camelspiders can move at speeds over 30 MPH, screaming while they run.

2. Camelspiders can be as large as a Frisbee.

3. Camelspider venom is an anesthetic that numbs their prey.

4. Camelspiders can jump 2 feet high.

5. Camelspiders get their name because they crawl into the stomach of camels and eat them.

The common camelspider in Iraq is somewhat larger than the species in southwestern U.S. (approximately 3 inches in length). The picture commonly found on the web is a gross exaggeration of this species. A friend of mine worked in the medical corps during the Iraq War.  He indicated they pose no danger to the troops or camels but there was a few troops who were bitten, which basically basically resulted insmall puncture wounds with no venom. These bites commonly occurred when the troops attempted to set up bet on fights between these arachnids and true scorpions. For some reason, most of the troops that participated in this came for the Deep South of the U.S. They don’t jump (the camelspiders, not the troops) and can possibly run a short distance at a speed of a mile or 2 an hour. And of course they don’t eat camel stomachs.

Camelspider from Iraq. Size is Greatly Exaggerated (really about 3 inches) by Angle of Camera.

Harvestmen-Daddy Longlegs. This group of fairly large arachnids is commonly confused with the daddy longleg spider.  Harvestmen differ from this spider in that the cephalothorax and abdomen are broadly joined. In spiders there is a narrow waist or petiole between these 2 areas; also unlike spiders, the abdomen is segmented in harvestmen. The most notable features of many harvestmen are the long, slender legs. Their eggs are spherical, about 0.4 mm diameter with a smooth surface and a color change from off-white to dark gray-brown as they mature. Eggs are laid in leaf litter and other suitable locations and in clusters ranging from 10 to several hundred.

 Ay one time or another, the daddy longleg spider is typically found in most homes in the United States. Of course, these 2 can be easily differentiated by a close inspection of their anatomical differences, but more simply by the presence of webbing. Harvestmen do not spin webs. The chelicerae of harvestmen are fang-like, but these arthropods are not strictly predators; instead they are scavengers feeding on dead and living plants, dead and living insects and a variety of other materials.

It is not uncommon to find large numbers of daddy longlegs congregated in a relatively small space. It is possible that these congregations are associated with mating. It has been reported that when a large group is contained in a closed space, they have a fatal effect on one another. This may be associated with a chemical that they release to repel predators. Perhaps in close quarters, a build-up of this chemical is too much for their systems to bear.

It is commonly believed that the bite of harvestmen are toxic to humans. Actually, the chelicerae of harvestmen are quite small, and an attempt to bite would not penetrate the human skin. Also there are no records of this venom being toxic to humans. It is possible that this belief stems from the fact that some harvestmen prey on black widows, and because the black widow is known to possess one of the more toxic spider venoms, it would logically (or illogically) follow that a daddy longlegs would need toxic venom to subdue their notorious prey. 20100626.jpg

Various Harvestmen Including an Aggregation. Top Left Image Courtesy jovengandalf CC BY-SA 2.0. Right Image Courtesy Luis Fernández García Creative Commons BY-SA 3.0. Bottom Image Courtesy Dschwen Creative Commons SA 2.5.

Whipless Whiptailed Scorpions. These arachnid belong to the order Amblypygi. They are active predators that are found in caves, deep leaf litter and similar situations, especially in tropical locations. As seen in the provided image, their pedipalps are modified for capturing and retaining prey-note large spines. The first pair of legs function as sensory organs and are not used for walking. The sensory legs are very thin and elongate, have numerous sensory receptors, and can extend several times the length of body. Amblypygi have 8 legs, but use only 6 for walking, often in a crab-like, sideways fashion. The front pair of legs is greatly elongated and serve as “feelers” for finding their prey as they lack compound eyes. When a suitable prey is located with these elongated front legs, they grasp its victim with the long spines on the grasping pedipalps. They then chew up and consume the captured prey with their pincer-like chelicerae.  Depending on species, they vary considerably in size with larger specimens reaching a 28 inch leg span. As gruesome as they look, they are considered harmless to humans

Courtship involves the male depositing stalked spermatophores or sperm masses on the ground, and using his pedipalps to guide the female over them. She gathers up the sperm and lays fertilized eggs into a sac carried under the abdomen. As with true scorpions, once the young hatch, they climb up onto the mother's back; any which fall off before their first molt will not survive. These predators mostly feed o a variety of arthropods, but larger specimens are capable and do on occasion fed on vertebrates such as small mice

File:Heterophrynus 02.jpg

Whipless Whiptail Scorpions. Top Image Courtesy Graham Wise Creative Commons BYSA 2.0. Bottom Dr. Kaae.


Call or email  in false answers.

Chapter 3 Questions- True/False 
5. The arachnids are the largest class of animals (exclusive of the insects), with 65,000 known species worldwide, and undoubtedly there are another million or so yet detected species. Its members exist nearly everywhere—often in considerable numbers.

6. The pedipalps and chelicerae are quite variable in the Arachnids and are used to distinguish orders of the animals

7.Most scorpion species in the U.S. are not typically dangerous, with a sting a little more painful than that of a bee.

8. Scorpions  are readily attrected to lights. As a result, if scorpions are a problem on a property, changing light around the structure  will be of value.

9. It is difficult to kill adult scorpions with most pesticides due to their thick exoskeleton.

10. Scorpions are hardy and can survive in extreme conditions includinmg temperatures as high asn 115 F, being frozen for weeks, total emersion in water for up to 48 hours and lack of food for up to 1 year.

11. The venom of the most toxic species of scorpions is reportedly 100,000 times more toxic than cyanide.  Fortunately little is normally injected.

12. In the United States, the sting of only 2 in the genus Centruroides can be considered dangerous and rarely result in human death.  These occur across much of the Southern United States down into Mexico.

13. In Arizona, the bark scorpion in the genus Centruroides is a dangerous species accounting for 75 human deaths from 1926 to 1996 and on a yearly basis far fewer since then.  Most of these casualties occur in children and babies.

14. Sunspiders can be quite aggressive and can produce a toxic bite.

15. Daddylongleg spiders spin untidy webs that are readily abandoned if they become dirty.  When webs are abandoned, the spiders immediately spin new webbing, thus accounting for the large amount of webs that can be found in a home with relatively few spiders. 

16. It is commonly believed that the bite of harvestmen are toxic to humans. Actually, the chelicerae of harvestmen are quite small, and an attempt to bite would not penetrate the human skin. Also there are no records of this venom being toxic to humans.

Mites and Ticks

Image Dr. Kaae

This is the second largest order (insects are first!) of plants and animals. Most experts believe there are over one million species of these arachnids that occupy nearly every ecological niche. For example, almost anyone reading this program is currently infested with mites. There is a small mite that lives in hair follicles and the sebaceous glands of the nose. They are harmless and should be of little concern. There are even mites that live in the lung cavity of the common garden snail and, unlike insects, mites occupy many areas of the ocean. The mites and ticks can be readily distinguished from other arachnids by their sac-like body. The abdomen is not distinctly segmented and is joined broadly to the cephalothorax. The mouthparts of these small critters are primarily for piercing a host and then sucking up juices.

Mites generally are quite small (most are smaller than a grain of sand). Some are microscopic. Because of the large number of species in this group, almost every conceivable feeding habit is exhibited. Mites are not only found in almost every ecological habitat, they are one of the most common creatures on earth. The basic life cycle of mites and ticks is egg, larva, nymph and adult.  The larval and nymphal stages look like smaller versions of the adult; however, the larvae bear only 6 legs each while the nymphs and adults bear 8.

Entomophobia and Delusory Parasitosis. These two distinct phenomena are both based on the fear of small creepy creatures. As the name implies, entomophobia is the fear of insects. Based on a national survey, the fear of insects is ranked third in adults—closely behind the fear of public speaking and death. The fear of cockroaches is frequently ranked number one in the insect world although, but I am sure bedbugs may be approaching their status or higher.  The fear of insects is a learned response. Very few children are afraid of insects unless they learn to be so by their parents, movies, or other sources. Because this is a learned response, this type of fear frequently can be reversed—sometimes with very little effort.

We have found that exposure to reptiles and insects is often enough to "unlearn" this fear. Once a young person can be persuaded to hold a walking stick and then to look into its "cute little face, they are halfway to undoing an acquired fear of all 6 legged animals. We have observed this behavior time and again due to our activity with youth fairs and other such public events. The annual county fair in Orange County, California has provided us the opportunity to educate children on a very large scale. Parents often know their own fear is irrational and don’t want to pass it along to their kids Therefore, the child’s acceptance often has a secondary benefit in that the parent accepts the animal as well. Once we plop a scorpion, python, or tarantula into the arms of a young person, the parent will usually take a deep breath and then accepts the animal.  Parents don't want their kid to think they are big "sissies."

We once participated in a youth exposition where management sent us a teenage girl to help out. Being deathly afraid of snakes, she probably was not the best volunteer for our type of exhibit! She assured us she would be all right as long as she didn’t have to go near anything reptilian. After a short period of time, she ventured a small caress down the back of our most beautiful snake. Then she had us hold its head so she could feel what the body felt like. Then she bravely held the whole snake. The snake, responding to a warm body in a cold room, coiled delicately around her arm and cuddled right up. By the end of the day, she wanted to take it home with her. For most people, this intimacy experienced with the previously feared insect or snake is enough to overcome many years (sometimes decades) of learned terror.

Delusory parasitosis is an irrational fear of small creepy non-existent creatures. Because mites are so small, in many cases this condition is diagnosed as a mite infestation. This phenomenon is more common than one might expect. Frequently, people who are inflicted with this malady are quite normal in all other phases of life and lead productive lives.

I was quite unaware of this phenomenon until one day a man in his mid-40 walked into my office and indicated that the UCLA Medical Center had referred him to me. He indicated that he and his home were infested with small 'bugs' that he could not eradicate. After a short discussion, he reached out into the air and indicated I had them in my office also. I responded that he must have brought them with him. He further stated that he had captured some and placed them on a piece of scotch tape. He related collecting each ‘critter.’ The first had bitten him on the leg and then disappeared under his skin, but he dug it out with a sewing needle. The second was on his pants cuff and bit him on the ankle. The third was found swimming around in his toothpaste. After considerable discussion, we examined each 'critter' with a microscope. Needless to say, none resembled an insect or mite. Indeed, they were small grains of sand, pieces of lint and so on. However, even after this close inspection and working with him over a several-week-period, he could not be persuaded that the attacking creatures were imaginary. The situation became so bad that he convinced his wife that she was also infested. They had arguments over who had the most. They couldn't get them out of their home even though several exterminators were called. Because of the infestation, the home was eventually sold at a considerable loss. Partly because of the turmoil, their marriage ended in divorce.

There have been many similar situations since then. One of the most unusual occurred a few years ago when a city official from Mission Viejo (Orange County) called me and indicated that he had a whole neighborhood infested with scabies mites (see below). Scabies are parasitic mites that commonly infest humans. At the time, this didn’t seem questionable because a number of the people had been to medical doctors and had been treated for this mite. These treatments didn’t seem to solve the problem, and I was brought in as a consultant. The main problem was centered on one particular resident. This woman apparently had convinced much of the neighborhood of the widespread infestation. She was using very drastic measures to try to eliminate these mites from her house and family. She would use lye to scrub down the beds on a weekly basis. On several occasions, she washed her kids down with gasoline. Of course upon hearing this, I began to realize that the whole situation was more than a little irrational. The final clincher was when she indicated that the whole problem started when she brought a potted plant back from Arizona, and while it was sitting in her bathroom, a pod grew out of it and blew these tiny critters all over the neighborhood.

A colleague from NCSU, Mike Waldvogel, reports similar experiences. He states he has received a variety of imaginary critters in vacuum cleaner bags, pillows cases, panty hose, skin samples, glue boards (like the one you use for catching mice) and (the one he described as the ultimate) a bottle (formerly a pint gin bottle) that was labeled "after douching." Needless to say that one wasn’t opened! Neither were the vacuum cleaner bags as they usually contain pesticide-laden dust from over treated carpets for these so called pests.

All of these cases have had several symptoms in common.The 'critters' typically fly through the air, crawl on the skin, frequently appear and disappear in the skin, make clicking noises and can be found in soap and toothpaste. Generally, inflicted individuals have gone to several medical doctors to no avail and can almost never be persuaded that the pests are imaginary.

Recently I started an expert witness website with the idea working on some court cases. That worked out OK but with success came some problems. I receive about one phone call a week from the general public about bird mite infestations.  Unfortunately, bird mites have become a big thing on the internet.  Apparently, once one person writes about a so called infestation of these critters in her or his home it catches on.  Needless to say 95% of the infestations that I hear about are strictly delusory parasitosis. To a person, all these callers are sure they have a bird mite infestation and cannot be convince otherwise.  I frequently ask them to send samples which turn out to be nothing. I generally tell these people send me something that they can see moving. Their response is" that according to the internet they are invisible to the naked eye".  Actually bird mites are small but clearly visible.

Scabies and Mange Mites. Sarcoptes scabei is a parasitic mite that attacks a wide variety of mammals; however, there are many varieties with each type being host-specific. For example, the variety of scabies that attacks humans does not infest other animals. Similarly, the scabies mites that attack dogs do no infest humans.  The human scabies mite is almost invisible to the naked eye (about 1/60 inch), cylindrical in shape, and has golf tee-shaped suckers on the tips of the legs.

 Female Human Sarcoptic Mange Mite (Sarcoptes scabei) Greatly Magnified. Image Courtesy of CDC Healthwise Photo Library.

The life cycles of male and female human scabies mites are somewhat different. A young fully developed female adult will crawl over the body until reaching soft, wrinkly skin and within a few minutes bores inward forming a tunnel about 3/4" in length and parallel to the surface of the skin. She feeds on the host's (you) body juices and lays eggs (up to 20 per female) in the burrow.  If closely inspected, mature females can be seen in the burrows.  As a result of this activity, pimple-like structures develop which eventually rupture after a day or two and release the eggs on the skin. Once hatched, the larval and nymphal stages crawl over the skin and periodically feed in sebaceous glands and hair follicles. Male mites also feed in these areas. It takes about two weeks to complete the life cycle from egg to adult.

Acquisition of this mite is typically by skin-to-skin contact with an infested individual. Such contact may be quite incidental such as holding hands. Very commonly, these mites are acquired from children and it is not unusual via sexually contact. On rare occasions, scabies mites are acquired via bedding or furnishings, but these mites can only survive for a few days off its human host.

When someone is infested, the majority of these mites (63%) are found on the hands between the fingers and wrists and approximately 11% on the elbows. In women, the mites are often found burrowing beneath and around the breasts and nipples. In young children, the mites can be found all over the body and frequently on the legs.


Top/Left. Close-up Photo of a Scabies Burrow. The Large Scaly Patch at the Left is due to Scratching. The Scabies Mite Traveled Toward the Upper Right and Can be Seen at the End of the Burrow-Round in Appearance. Image Courtesy Michael Geary Public Domain.  Top/Right. Symptoms of Scabies Infestation on Hand. Image Courtesy Steschke CC BY-SA 3.0. Bottom. Common Locations of Symptoms-Marked in Red. Image Courtesy Steschke CC BY SA-3.0.

There are no obvious symptoms for the first 30 days after infestation.  However, an intense rash and itching begins to occur over many areas of the body. These can occur even in areas where the mites are not found. The itch is characteristically more severe at night and affects the trunk and limbs. It does not usually affect the scalp. Itching can become so intense that the infested individuals lose sleep and can be affected mentally. Blisters and pustules on the palms and soles are characteristic of scabies in infants. Secondary infections commonly complicate the signs of the presence of these mites and can results in crusty patches and scratched pustules. After about 100 days, the mite population drops off and, symptoms of the infestation begin to disappear.

Treatment consists of elimination of the mites from the body and treatment of recently worn clothing and bedding. The mites are totally host dependent and cannot live off the host for more than a day or two. Pesticide lotions can be used to kill those mites on the body.  Kwell lotion was the standard for control for many years.  However, due to possible negative side effects of the active ingredient, it has been mostly replaced with more effective products. Permethrin cream is now the most commonly recommended treatment lotion. Recently used clothing or bedding should be laundered, ironed or sealed in large plastic bags for a few days. Symptoms will not disappear completely for a few weeks after the mites are eliminated.  This is significant because it is not a good idea to over-treat an infestation of these mites.  One of our grandkids contacted scabies and the kids next door had the same problem.  We instructed the neighbor how to treat her kids.  A week later, she indicated that the symptoms had not disappeared and wanted to retreat her kids. This is not a good idea as exposing children too frequently to the prescribed pesticide lotion can lead to over medication. Therefore, it’s important to know and to follow the directions for such direct contact treatments.

It should be mentioned that medical doctors frequently misdiagnose scabies mite infestations. As discussed above, several of the neighbors of the lady suffering from delusory parasitosis were convinced by her that they had scabies and were actually diagnosed and treated for them. I was once suffering from itching of the skin and went to a M. D. who immediately, upon hearing my symptom, stated that I had scabies and prescribed Kwell. I told him that I really didn’t have any of the other symptoms other than itching. His response was "sometimes there are no other symptoms," which may or may not be true. The point is that he didn’t even look at me. Upon hearing "itching" he stepped back about two feet (they are fairly contagious) and muttered "scabies.” After using the Kwell with no relief, I consulted a dermatologist who correctly diagnosed my problem as dry skin.

I was recently contacted by a convalescent home about a scabies infestation. They had approximately 100 patients, half of which were diagnosed with scabies.  This was a real problem.  Public Health had quarantined the hospital because this is a communicable disease.  Of course this was devastating and confusing to the older residents as well. Their relatives couldn’t visit them. The people who worked there were very concerned and fearful that they might carry the disease home with them and give it to their own families.

With this in mind, the hospital wanted me to come up with a viable treatment program. Treatment was several folds. Everyone involved had to be treated with Kwell lotion-the chemical that at that time was preferred. Treatment included all the patients and individuals who worked there due to the fact that symptoms of an active infestation do not appear immediately. There was no need to treat the premises itself because the mites are host-dependent and can only live off the host for a day or two. However, recently worn clothing and bedding had to be treated as a potential source of infestation. We considered sending these to a commercial laundry, but that created the potential of infesting the individuals who worked there.  Instead, we took all the clothing and bed sheets and sealed them in large trash bags for 3 days keeping in mind that the mites can only survive off the host for a day or two.

Housedust Mites. These are not visible to the naked eye and are not typically found in house dust. These arachnids feed on human dander (sloughed skin) and thus are found in areas of the home where this material accumulates such as in beds or sofas. They tend to be more common in humid areas and where cotton is used as stuffing in furniture. Housedust mites do not bite but have been implicated in certain types of allergies in humans. These arachnids at one time or another infest most homes in many parts of the country.

Common House Dust Mite Greatly Magnified. Image Courtesy of ARS.

One major mattress companies has an advertisement on TV that states that the weight of an average mattress in the U.S. doubles in 10 years as it fill up with house dust mites. They also claim that their mattresses are built so well that these mites cannot get inside them. Both of these statements are ridiculous. First of all house dust mites do not get inside mattresses and if they wanted to I doubt that they would have any problem considering their size. Secondly, a queen size mattress weighs around 60 pounds. Sixty pounds of housedust mites would be in the billions and there is no way there would be enough food (dead skin) to support a population of that size.

Chiggers. This is a group of mites that are parasitic on humans, turtles, snakes, chickens, rabbits, and many other animals. Adults and nymphal chiggers are typically free-ranging scavengers associated with the soil and commonly are found in grasslands meadows and wooded areas. Chiggers are present in Southern California but are much more common in the southeastern United States and many tropical areas of the world.

An Adult Chigger. Image Courtesy Susan Ellis, Bugwood.

There was an occasion when a pilot was flying at an elevation of around 1,700 feet when he spotted a reddish color covering approximately 2 acres. Upon landing, he surprisingly discovered a heavy emergence of the giant red velvet chigger adult (each about the size of a large dot).  Keeping in mind that these mites are “giant,” but no larger than the size of an o on this page, the estimated population was approximately 3 to 5 million with an average of 50 mites per 4 inch square.

Chigger eggs are typically deposited in clusters in the soil or under rocks. Upon hatching, the parasitic larvae accumulate on stones, vegetation, or other object and wait for a passing host. Chiggers and other ectoparasites recognize a host by 3 means. These are the host’s movement, heat and odor in the form of carbon dioxide. Chigger larvae are extremely small and less than 1/150th of an inch in diameter. Several thousand of them could line up across this page and still leave room for 2 or 3 hundred more. At this size, chigger larvae are almost invisible to the naked eye. However, when several chiggers cluster together on the victim body near an elastic waistband or wristwatch, they can be seen because of their bright red color.

One of the common misconceptions is that the larvae of these mites burrow under the skin and ultimately die within the tissues thus resulting in persistent itch.  These tiny larvae attach by inserting their minute mouth parts into skin depressions, skin pores, wrinkle or hair follicles. Their mouthparts are tiny, short and delicate and can penetrate only thin skin or skin wrinkles or folds. Typically, chigger bites are found behind the knees, on the ankles, near the crotch, beneath the belt line and in armpits. Of course this is mainly because these are areas of the body where the skin is soft and are not located high on the body. The insertion of the mouthparts is not felt or the source causing itching. A feeding chigger usually goes unnoticed for 1 to 2 hours after attached.  While feeding, the chigger injects powerful digestive saliva which after a few hours causes the skin to react and form a hard tube-like structure called a stylostome. This structure walls off the corrosive saliva, but it also functions like a feeding tube for the chigger larva. The larval mouthparts are attached to the stylostome, and like a person drinking a milk shake through a straw, allows the larva sucks up liquefied body tissue. The chigger continues alternately injecting saliva into the bite and sucking dissolved liquid body tissue.  Irritation and inflammation of the surrounding tissue is the result of the presence of the stylostome. The longer and deeper the chigger feeds, the deeper the stylostome grows, and the larger the welt will eventually become. Individuals see a small red dot inside a welt (usually under a water blister), but this is the stylostome tube and not the larval body. bite.svg

Chigger Life Cycle and Larva Feeding Vis Stylosome. Images Courtesy Bugboy 52.4 Public Domain.

If undisturbed, these mites typically require a few days or longer completing a feeding. In the case of humans, chiggers typically do not finish feeding since they are accidentally brushed or scratched away by the victim prior to completion of the meal. The characteristic intense itching reaches a peak a few days after the bite occurs. This is the result of the stylostome remaining inside thr tissue long after the chigger larva has dropped off the host. The skin may continue to itch for many days due to an allergic reaction to stylostome. The stylostome is eventually absorbed by the body. This is a relatively slow process that can take week or longer.

One opinion is that females and children are bitten more commonly than men. However, it is documented that all 3 typically collect equal numbers of chiggers while walking in the woods. However, women and children typically have thinner skin and as a result have more acceptable surface areas that chiggers can easily bite.

The first technique to avoid against chigger attack is to wear the right kind of clothing. Tightly woven socks, high shoes or boots and long sleeves and pants are preferable to sandals, shorts and the like. Tucking pant legs inside boots or shoes and buttoning cuffs and collars in shirts also helps keep the chiggers off the body. Regular mosquito repellents will repel chiggers. All brands are equally effective but the higher the concentration of the active ingredient of DEET, the more effective is the product. These products can be applied to exposed skin and around the edge of openings in your clothes, such as cuffs, waistbands, shirt fronts and boot tops.  Unfortunately, many of these repellents are only potent for two to three hours and must be reapplied frequently.

People who live in chigger-infested areas may develop immunity to the bite of these arachnids. Humans who have been exposed to chigger bites over a period of years may develop a hypersensitivity to their saliva. Hence, when they are newly bitten, a huge tissue hardening occurs (rather than the feeding tube) that immediately prevents further penetration of the skin; thus, little saliva is injected and no further symptoms may occur.

Ear Mites. This is a group of parasitic mites that attack a variety of animals (cats, dogs and rabbits). In these animals, infestations are limited to the ears and the mites are typically found feeding in the outer ear canals. As do most parasitic arthropods, ear mites are host-specific and no species attack humans. In rabbits, infestations can become serious if left uncontrolled. The result can be bleeding, secondary infection and possible death. In rabbits, an infestation is easily recognized by a layer of dried ooze on the inner side of the ear. If this crusty ooze is removed, large numbers of mites can be found feeding on ear tissue.

As discussed, ear mites are common in dogs and cats. Young animals appear to be more susceptible to the feeding of these arachnids. Typical symptoms include frequent shaking of the head, lowered ears (in cats), and black coloration in the outer ear canal (this gives the appearance that the animal has very dirty ears). In all cases, a few applications of several drops of mineral oil to the infested area will give considerable relief and control. Most veterinarians suggest this should be followed by applications of medications specifically used for ear mite control. It should also be noted that bacterial and fungal infections of the ears result in similar symptoms.

Human Follicle Mites. Follicle mites are long and skinny with short legs. These microscopic mites infest a number species of mammals and exhibit have a high degree of host specificity (i.e., mites from one host species will not infest other species). The majority of humans are infested with Demodex folliculorum. They are commonly found living in hair follicles and sebaceous (oil) glands, especially on the face (in and around the eyes, nose, and forehead). In cases where these mites are a problem, they are most often associated with skin rashes, ache and loss of hair (particularly the eyelashes).

In other animals, infections with these mites can be a serious problem. Dogs that are infected with Demodex canis (the dog follicle mite) can result in a condition called red or canine demodectic mange.  This can result in significant loss of hair and skin rashes.  In severe cases infected dogs may be euthanized.

 A Human Follicle Mite.  Image Courtesy of Life Science Department, University of South Africa.

Phytophagus Mites. These are a large group of mites that are plant feeders (phytophagous). The most common type of these is spider mites that typically feed on the undersides of leaves by puncturing the plant surface with their mouthparts and sucking plant juices. These are not only a major pest of many agricultural crops but also attack most types of houseplants.

The most obvious symptom of feeding by spider mites in the early stages of an infestation is a fine speckling that appears on the upper surface of the leaf. As the infestation advances, fine webbing results. Generally, by that point, the plant is beyond saving.

 Image Greatly Magnified Spider or Two Spotted Mite.  Image Courtesy of ARS.

The main predators of spider mites are other mite species. It is therefore important to be able to distinguish predatory mites from phytophagous forms. As with other arthropod groups, predators are quite fast while plant feeding forms move slowly or are nearly stationary. A good rule of thumb is if you can easily see it moving, it is a predatory mite. Plant feeding mites are best controlled with an acaracide. Some degree of control may be achieved by periodically washing the mites off the plant with a mild soapy water solution.

Phoretic Mites. Phoresy refers to the process of “hitchhiking” that occurs mainly in the arthropod world. This process typically is the result of the development of unfavorable environmental conditions. Phoresy is common in small, flightless arthropods that are not readily capable of changing their environment. In these cases, they merely attach to other arthropods (especially flies and beetles), go for a ride and drop off when encountering more favorable environments. Because of their small sized and absence of wings mites and pseudoscorpions hitchhike on larger insects.

Left Phoretic Mites on Fly and Harvestman. Image Courtesy of Alvesgaspar GNU Free Documentation. Right.Soebe - German Wikipedia, CC BY-SA 3.0, https://commons.

Ticks.  Ticks are of considerable economic importance. They suck blood and vector a number of diseases to humans and other animals. These arachnids may be distinguished from mites by their large size and leathery exoskeleton.

 Typical Hard Tick Prior to Feeding. Image Dr. Kaae

There two families of tick are the hard and soft ticks. The soft ticks almost exclusively attack birds and are of minimal concern to the general public. Hard and soft ticks pass through 4 developmental stages. The eggs of most hard ticks are deposited in clusters in protected locations such as in the soil; there may be as many as 7000 eggs in a single cluster. Upon hatching, the 6-legged larvae (seed ticks) crawl up on vegetation or other structures and wait for a passing host. Once attached to a host, they burrow their heads below the skin and begin to suck blood. Hard ticks feed to engorgement swelling with blood to many times their original size. They feed continuously for a day or more before dropping to the soil and eventually molting into the 8-legged nymph. The nymphal and adult stages repeat the process of waiting for a host and feeding to engorgement. The female adult requires a large blood meal in order to produce her massive number of eggs.

File:Ixodid wynaad.jpgIxodes ricinus (engorged)

Top. Hard Tick unengorged with the Blood of its Hosts. Image Courtesy Richard Bartz. CC BY-SA 2.5. Bottom Image Engorged Tick Courtesy of L. Shyamal CC SA 3.0.

The length of development from egg to adult with most hard ticks depends primarily on the availability of food and requires anywhere from a few months to longer than a year. The larval or nymphal stages may have to wait for up to several months for a passing host. Apparently this has little effect on survival as these stages generally can live 300 or more days without feeding.

Most ticks require separate hosts to complete their life cycle and are referred to (surprise!) as 3-host ticks. A few species will remain on or near the same host during the larval and nymphal stages but seek another host during the adult stage and are referred to as 2-host ticks. One-host ticks spend all 3 stages on the same type of host.

The brown dog tick is probably the most widely distributed tick species occurring throughout the United States and in much of the world. This species is found in both tropical and temperate climates. It is a 3-host tick and prefers to feed on dogs; however, it occasionally feeds on other animals such as horses, cattle, and (rarely) humans. This species is unique in that it is commonly found and breeds in protected locations such as homes and kennels. Unfortunately, it is not that uncommon to encounter large infestations in homes. 

The authors encountered a huge infestation of this tick in a one-bedroom apartment; the owner had gone on vacation and left a German shepherd in a kennel. An impregnated female tick attached itself to the dog and was brought home. The tick dropped off the dog and deposited from 2000 to 3000 eggs in the house. Because the ticks had a continuous source of food (the dog) and a favorable environment, development was fast. Over 400 ticks were vacuumed from the living room. Because the preferred host was present (the dog), none of the residents were bitten. However, ticks commonly were found crawling around the apartment and frequently were squashed accidentally thus leaving blood spots on the furniture and beige rug.

The wood tick is another 3-host species that commonly occurs in the forested areas and scrubland of California and other western states. It commonly attacks humans and is the main vector of Rocky Mountain Spotted Fever. The disease is occasionally found in the Rocky Mountain States but rarely occurs in California. Besides vectoring Rocky Mountain Spotted Fever in the Rocky Mountains states, the feeding of female wood ticks around the cranial areas occasionally results in tick paralysis in humans and other animals. This paralytic condition is the result of injection of the tick' saliva. It can be fatal with excessive feeding, but normally once the tick is removed, recovery is complete.

If a tick is pulled off the host while it is feeding, its mouthparts may be left in the wound and a secondary infection or blood poisoning could result. The basic premise behind proper tick removal is to provoke the tick to withdraw its mouthparts. It was once thought that touching a hot match or needle to the back of the abdomen was an effective means of tick removal. This technique is no longer recommended as it may cause the tick to regurgitate which can transmit disease causing organisms. Today, coating the tick for a short time in Vaseline or careful removal with forceps are the recommended methods.

Lyme Disease. This disease was first diagnosed in 1969 in the United States in Old Lyme, Connecticut. It now occurs in 43 states. Nationwide it has quickly increased from 2,300 human cases in 1986 to 7,400 in 1989. Since then the number of cases in the United States has increased steadily.  Lyme disease has not been found in Southern California, but is prevalent in Northern California and in the eastern United States. In California the western black legged-deer tick is the primary vector of this disease.

The symptoms of Lyme disease initially include a rash which develops anywhere on the body from 3 to 30 days after the initial bite. Shortly after, large doughnut shaped blotches typically develop at the site of the bite. Weeks to months later a number of chronic conditions may occur. These include malfunction of the limbs, facial paralysis, heart abnormalities, arthritis, migratory pain in the joints and deterioration of the bones.

 Typical Early Symptom of Lyme Disease-Donut Shaped Rash.  Image Courtesy of CDC Healthwise Photo Library.

This disease rarely results in death, but if it is allowed to advance can be debilitating indefinitely. It is important to be able to diagnose this disease during the initial symptoms. If so, it can be treated successfully with antibiotics. Treatment is much less successful in the advanced stages. In states where this disease is prevalent, it is best to apply repellents (OFF) around the ankles and pant cuffs while in those areas where ticks are found. The authors know several individuals from Southern California who contracted the disease. In their cases, the disease was contracted in the Eastern U.S. or in Northern California. An important factor is that when they came back to Southern California, their doctors had a rather difficult time diagnosing the disease as they had not seen very many cases.

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Questions- True/False


18. The ticks and mites are the second largest order (insects are first!) of plants and animals. Most experts believe there are over one million species of these arachnids that occupy nearly every ecological niche.

19. Housedust mites are not visible to the naked eye and can be found in peoples’ beds.

20. Housedust mites do not bite but human can develop allergies to their presence.

21. Delusory parasitosis is a paranoia, or irrational fear, of small creepy non-existent creatures.

22. Scabies is nearly always acquired by skin-to-skin contact with an infested individual.

23. Housedust mites feed on dander and can cause allergic reactions in humans. They cannot be seen with the naked eye.

24. One TV advertisemen claims the a bed can double in weight due to the presence of housedust mites-obviously ridiculous.

25. Phoretic refers to the behavior of mites and other small arthropods hitchhiking on larger insects.

26. Scabies mite infestions almost always startsa with contack with another infested individual.

27. When someone is infested with scabies mites, the majority of the mites are found beetween the fingers and on the wrists. On women they can also be found on the breasts. Children may ge them on many prarts o their body.

28. Sarcoptes scabei is a parasitic mite that attacks a wide variety of mammals; however, there are many varieties with each type being host-specific. For example, the variety of scabies that attacks humans does not infest other animals.

29. Doctors frequently misdiagnose scabies infestations.

30. The main biological control agenst of phytophagus mites are predatory mites. These can easily be distinguished from the plant feeding mites by the fact that they move much slower than their prey.

31. Bird mites cannot be seen without magnification.

32. Clover mites occasionally invade home in larege numbers. They do not bite.

33. Clover mites can reproduce once found in a srucuture.

34. On occasion large number of the brown dog tick can be found and even reproduce in homes.

35. The brown dog tick does not readily feed on humans.