Spiders (CD Sample)

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Arachnids-Spiders

The spiders are a large group of arthropods with about 3,000 North American species. In spiders, the cephalothorax is joined to the abdomen by a narrow stalk, or petiole. The chelicerae are fang-like, hollow and have attached poison glands. The pedipalps are short and leg-like, frequently bearing opposing teeth which are used for crushing food. Many male spiders have clubbed pedipalps that are used to transfer sperm to the female. Spiders have from 2 to 8 simple eyes. However, a few cave-dwelling species are totally blind. The spinnerets (a silk producing apparatus) are located on the underside of the abdomen.

These arthropods are much more common than one might expect and, consequently, are quite important in controlling insect populations. For example, one study in Great Britain counted 130.8 spiders per square meter of meadowland. An average spider (if there is such a thing) consumes 0.09 grams of insects per day. After some calculations, one author concluded that in the Netherlands, with an area of 36,150 square kilometers and 15 million human habitants, there are 5,000 billion spiders. He further concluded that based on the total weight of insects that this number of spiders could consume, they could consume the equivalent weight of all the Dutchmen in that country in 3 days. Luckily for us spiders do not eat humans!

Spider silk is an extremely strong material that, on an equal weight basis, is stronger than steel. One scientist suggested that a pencil-thick strand of silk could stop a 747 in flight. It is used by spiders for many different activities, including the construction of egg sacs and webs, as a lifeline when jumping or dropping to escape, for wrapping their prey and transferring semen from the abdomen to the male’s palp and as a shelter in which a spider can retreat. The silk is produced by the silk glands as a liquid that hardens when released from the spinnerets. Silk is elastic and only breaks when stretched 2 to 4 times its original length. Spiders frequently recycle silk (eat the old silk) which is very important for those that form large webs, such as the orb web spiders. In these cases, webs are easily destroyed and after a few days the droplets that bind them lose their adhesiveness. Dupont Corporation is studying spider silk. By using recombinant DNA technology, they managed to produce analogs of silk in yeast and bacteria and are planning to use this synthesized material for many kinds of construction purposes.

The jaws of a modern spider (Figure 4A) are used to grab and crush prey. Most spiders use poison to kill their victims. At the end of the fangs are 2 syringe-like structures that are hollow and quite sharp. These are used to puncture the body of a victim and inject the venom.

The fangs of a spider
Figure 4A. The fangs of a spider.

Unlike humans who digest food mainly after it reaches the stomach, spiders have what is referred to as external digestion. Injected enzymes dissolve the prey. Then it is sucked empty, leaving nothing but a few bits and pieces. Between the mouth and stomach there is a filtering device that is made up of thousands of fine hairs. Only the very smallest of particles can pass through this filter. This device is so fine that even the particles in India ink will be filtered out so that only liquids pass through. With these filters the spider prevents bacteria, viruses and other harmful life forms from entering its own body.

Because the food can be large in comparison to its own body volume, the spider’s abdomen can swell enormously. Excess digested proteins are stored making it possible for a spider to live for several weeks off a single prey. Waste materials are chemically converted to harmless crystals that are stored in special cells. In some orb web spiders, groups of these cells can be seen on the top of the abdomen and appear as white spots (Figure 4B).

Figure 4B. An orb-weaving spider illustrating the storage crystal (white) of waste products. 
Figure 4B. An orb-weaving spider illustrating the storage crystal (white) of waste products.

Dangerous Spiders

Black Widows
The black widow spider (Figure 4C) is found in every state of the country with similar species throughout much of the world. There are a few species of widow spiders belonging to the genus Lactrodectus in the United States, each being marked slightly different and all of which have a fairly toxic bite. Lactrodectus mactans is the species most commonly associated with the name black widow and occurs is throughout the U.S with the possible exception of the most northern extremes. There are different species in the genus Lactrodectus that are found throughout the world, all of which also possess a toxic bite. In Australia it is the red-back: in Mexico it is the arana capulina; in New Zealand it is katipio; and in France it is malmiginette.

Figure 4c 1Figure 4c 2 
Figure 4C. Female black widows, Lactrodectus mactans. Right image of gravid female (full of eggs)-Image courtesy of CDC Photo Library-Johm Gathaway.

Only the female of the species is dangerous and is named after the practice of killing the male immediately after copulation. In actuality, the female is usually pretty well fed and, more times than not, the male escapes before being consumed. The males (Figure 4D) are several times smaller than the female and brownish in color with pearly markings on the top of the abdomen. As with many spiders, the male’s pedipalps are club-shaped and used to transfer sperm to the female.

Figure 4D. Comparison of size-male and female black widow. Image courtesy of Peter Chew, Brisbane Insects. 
Figure 4D. Comparison of size-male and female black widow. Image courtesy of Peter Chew, Brisbane Insects.

immature females are often brown and striped with white colored markings. All stages (except the youngest spiderlings) have a red marking on the underside of the abdomen. This red marking serves as a warning coloration to potential predators. Bright coloration in most animals serves the same function, advertising the fact that an animal is potentially dangerous and to stay away. The black widow female hangs upside down in her web thus making this marking clearly visible.

The female is nocturnal and lies in wait on the web for trapped prey. The male typically is not found in the web but hunts either for food or a female. The web is uniquely and characteristically irregular in shape, strong, and produces a crackling sound when probed. The female can produce from 1 to 10 marble shaped white egg sacs in the spring. These eggs hatch within 10 days or so, with the young spiderlings remaining inside the sac until after their first molt. The 200 or so young spiderlings typically leave the sac about 30 days after when the eggs were first deposited. Upon emergence they feed on mites and small insects. Of course, the spiderlings are too small to bite humans and present no hazard from that standpoint. However, they do contain a toxic material in their bodies and, if accidentally consumed (the egg sac containing spiderlings) by a child or dog, the possibility of poisoning does exist. The life cycle is completed in 4 to 6 months with the adults surviving an additional several months. These spiders can be found in many situations but common environment requisites include high humidity, food and dark protected locations.

As with other spiders, black widows balloon or parachute as spiderlings. They typically crawl up on a twig or other surface and shoot long strands of silk out of their spinnerets. Air currents pick up this webbing and carry off the attached spiderlings. With the heat of the day the floating spiderlings are carried upward as high as a mile or so. As temperatures cool and wind turbulence decreases at night, they float back to earth. If they reach the prescribed environmental conditions they survive, if not they die. In actuality very few young survive to adulthood; however, because the female can produce as many as 2,000 or more during her lifetime, only 2 need to survive to replace the parents and perpetuate the species.

These spiders are not typically aggressive except in defense of the egg sacs. The fangs of a mature female black widow are quite small and incapable of penetrating thick skin. Consequently, in order to inject venom, a female black widow must bite humans on the soft parts of the body. The bite of this spider is rather painless at first; however, a systemic effect soon develops. The neurotoxin venom of a black widow is said to be 15 times more powerful than that of a rattlesnake. However, there is much less toxin, so the bite is normally not nearly as bad as that of the snake. Pain begins after 1 to 3 hours and continues for 24-48 hours. Pain often starts in the lymph nodes (groin, armpits) and spreads to the lower back. The stomach muscles develop severe cramps due to rigid contractions. The skin feels clammy, blood pressure drops, and profuse sweating and nausea may develop. Additional symptoms include facial muscle spasms, breathing difficulties and convulsions.

In humans, the mortality rate is approximately 5% of untreated bites by an adult female black widow. Most deaths occur in young children (more venom per body mass) or individuals who are already in poor health. The most common location where black widow bites occur in Southern California is outdoor bathrooms. The area right under the toilet seat is dark, humid and abounds with flies. So, in the springtime when the female is guarding her egg sacs and an unsuspecting human wiggles her web with soft body parts, it can be quite surprising (ouch!).

There is an antivenin available for bites. This is not always given as it can only be taken once. Frequently hospital patients are given Demerol or something else for the pain if the bite doesn’t seem to be too serious or life threatening. The antivenin is quite effective; however, it is not always advisable to use this on all patients as some may develop an allergic reaction.

Black widow antivenin is produced by a fairly complicated procedure. There are a number of small companies that raise black widows by the thousands. Applying a mild electrical shock stimulates the female spider to exude a tiny drop of venom from each fang. Subsequently, this venom is collected with small capillary tubes and saved. The venom from each company is pooled in the U.S. to make the antivenin. This is accomplished by injecting small amounts of the venom into horses that possess a degree of natural immunity to this toxin. After a few weeks when the horses have developed even more immunity as a result of exposure to the venom, serum is condensed from their blood to make the antivenin.

As previously mentioned, occasionally individuals treated with antivenin will develop allergic reactions. One such reaction is to develop hives and other symptoms when eating beef. Apparently, at least some of the protein in beef is the same or similar to that in horse blood serum. As a consequence, an allergic reaction unfolds in some cases when beef is consumed.

The brown widow spider, a close relative of the black widow, has recently received considerable attention and has been accidentally introduced Orange County, California and other parts of the country. Although belonging to the same genus as the latter the bite of the brown widow typically results in some pain and swelling but lacks the other symptoms from the bite of the black widow. These spiders are very similar in appearance to the black widow but differ in that their legs bear a degree of striping. More strikingly the surface of the brown widow egg sac is distinct spiked (Figure 4E) where that of the black widow is rounded in appearance with a smooth surface.

Figure 4E. A brown widow female with an asymmetrical and spiked surface egg sac 
Figure 4E. A brown widow female with an asymmetrical and spiked surface egg sac

Figure 4F. A comb footed spider-similar in appearance to black widow
Figure 4F. A comb footed spider-similar in appearance to black widow

Recluse, Violin or Fiddleback Spider. 
Spiders in the genus Loxoceles belong to a unique family known as the six-eyed sicariid spiders. These spiders all have 6 eyes (rather than the normal 8) that are arranged in a horseshoe pattern in 3 clusters of 2 eyes each. The family not only contains the genus Loxoceles, but also the six-eye crab spiders (genus Sicarius) of Central and South America and South Africa (discussed later). This is the first group of spiders that were discovered to cause the condition known as necrotic arachnidism. This term refers to the main symptom caused by a bite of these spiders, namely rotting of the flesh (Figure 4G). A physician in 1872 associated this symptom with the bite of the Chilean recluse spider. Up to that point the condition was referred to as gangrenous spot. In the US it wasn’t until 1957 that necrotic arachnidism was associated with the bite of the brown recluse spider.

At least 56 species of the recluse spiders have been identified, 54 of which occur in the Americas. Outdoors these species typically are found beneath fallen debris and rocks. They also do well indoors and typical locations include but are not limited to behind picture frames, in fold of clothing, boxes and shoes. Storage areas are common locations where the spiders are least disturbed. Most recluse spiders are rather timid and are reluctant to bite unless disturbed and do so in defense.

In the United States there are 11 native species of recluse spider and 2 imports from South America. The most notable of these are the brown recluse, Loxoceles reclusa (Figure 4G), which is commonly found in the central and south-central states and Loxoceles laeta or the Chilean brown spider (also known as the South American violin) which was found in Los Angeles a number of years ago. Recent identifications are non-existent. The brown recluse was once established in California but there is considerable controversy as to whether or not it still exists here. The medical community annually reports treating many bites from the recluse spider. However, some spider experts claim this spider no longer exists in California. Because little is known about the effect of the bite of many spider species, it is quite possible that these medically treated cases are not due to the recluse but any of a number of other spiders or, in many cases, are not due to the bite of any spider at all.

On the other hand this spider is fairly common in many of the US states. My office partner used to teach at Kansas State and his secretary and her husband purchased a house in the rural areas of the state. The first week they moved in she was bitten and the second week so was her husband. Apparently these spiders were spread throughout the house.

 
Figure 4G. Left. Symptom of bite of brown recluse. Left. The brown recluse, violin or fiddleback spider. Images courtesy of CDC Healthwise Photo Library.

The adult brown recluse (also known as the fiddle back spider or violin spider) is a small-to-medium sized (1/2-inch body length) spider that is yellow to brown in color with distinctive violin shape markings on the top of the cephalothorax. The appearance of the violin marking is not sufficient to identify this spider. There are other common spiders with similar markings. The six-eyes plus the marking are more useful. The web is medium sized, irregular in shape with thick strands and is not typically used to trap insects but rather more as a retreat.

Both the males and females are dangerous. The venom causes a local, necrotic reaction. The victim may not feel any pain for 2 or 3 hours after the bite or a painful reaction may occur immediately. In this case a stinging sensation is usually followed by intense pain. A blister forms as well as a painful, reddish margin. The tissue at the center of the bite becomes necrotic (rotting of the flesh) and involves the skin as well as subcutaneous tissue. In some cases the necrosis continues to increase resulting in a huge open sore that can reach several inches in diameter. The healing is very slow (up to several months) and often leaves an extensive scar.

Systemic (overall body) effects are not too common to this species, but may include chills, nausea, fever, muscle pain and other flu-like symptoms. In severe cases convulsions may occur along with abnormalities in the clotting of the blood. Damage to the red blood cell walls, resulting in leakage of hemoglobin, occurs in some cases. This can result in death due to renal failure as the kidneys attempt of deal with the damage red blood cells. There is no antivenin available, but the bite is often treated with corticosteroids and removal of the bite area. In advanced cases the lesion may become so large that amputation of limbs may be necessary.

MOST DANGEROUS SPIDERS IN THE WORLD

The Sydney Funnel Web Spider
This spider (Figure 4H) is reported to be one of, if not the most, deadly spiders in the world. This Australian spider has gained the reputation of being extremely aggressive. When confronted, the spider will rise up on its hind legs, lunge forward and bite repeatedly if given the chance. The fangs are large, powerful and capable of penetrating a fingernail. The venom of the smaller male is several times more toxic than the female's. This is unfortunate because the males tend to leave their burrows and roam freely, especially following heavy rains. As might be expected this spider gets its name from the fact that it occurs around the Sydney area.

Following a bite from this spider, symptoms develop quite rapidly; these include nausea, vomiting, heavy sweating, and finally, collapse. Unbearable cramps develop along with severe pain in the limbs. The lungs become quickly filled with fluids, causing cyanosis (turning blue) due to the lack of available oxygen. The victim eventually convulses and lapses into a coma, frequently dying, especially if very young. Fortunately, a very successful antivenin has been developed.

Figure 4H. A Sydney funnel web spider. One of the world’s most dangerous spiders.Image courtesy of Queensland Museum 
Figure 4H. A Sydney funnel web spider. One of the world’s most dangerous spiders. Image courtesy of Queensland Museum

The Six-eyed Crab or Sand, Spider
This spider belongs to the genus Siciarius, which is a South African living fossil that pre-dates the Gondwanaland drift some 100 million years ago. Also occurring in South America, these are large spiders approaching 2 inches in length with a leg span of 4 inches. This is a flattened species, which spends much of its time buried beneath the surface of the sand waiting for a potential meal. To bury itself, it raises its body, digs a hole, drops in and then covers itself in sand with its front legs (Figure 4I).

Sicarius hahni from the Northern Cape is possibly the most lethal species of spider in the world. Fortunately, due to its habitat, it is rarely encountered and appears reluctant to bite. Less fortunately there is no antivenin for a bite, making the bite much more hazardous than that of the Sydney funnel web where an antivenin is available.

 
4I. Six-eyed crab spider above and below sand. Image courtesy of Museum of Cape Town.

The Brazilian Wandering Spider
This spider is regarded by some as the most dangerous spider in the world. It is highly venomous, very fast and aggressive. However, recent studies indicate that these spiders only inject venom in about one-third of their bites and may only inject a small amount in another third. Thus the effects of the bites from these spiders can range from only a couple of pin pricks to a full-blown problem. The Sydney funnel web spider apparently injects venom in every bite and may thus in effect be more dangerous- although either spider's venom can lead to a medical emergency.

The Brazilian wandering spider is reputed to occasionally hide in clusters of bananas. As a result, any large spider appearing in a bunch of bananas should be treated with care. This spider should not be confused with the “other” banana spider or Huntsman spider that is discussed later in the text. It is called the wandering spider because it wanders the jungle floor, rather than residing in a lair or maintaining a web.

SPIDERS THAT ARE NOT DANGEROUS BUT OCCASIONALLY BITE

Tarantulas
One of the most notorious groups of spiders is the tarantula (Figure 4J). Because of their large size, Hollywood and the motion picture industry have exploited these spiders. In the movies, when a tarantula bites someone, the typical reaction is immediate death. Actually most tarantulas are docile, reluctant to bite and make nice pets. There are very few species considered dangerous to humans. The bite of the average tarantula worldwide is no worse than a bee sting. Generally speaking, the larger the tarantula, the more venom is injected. Thus, although often undocumented, the bite of some of the giant South American species could cause considerable pain, swelling and tissue degeneration in humans. The bite of any tarantula generally results in a deep puncture wound due to the relatively large fangs (Figure 4K) and should be treated with a tetanus shot.

The origin of the name tarantula has an interesting history. The name was originally given to a species of spider that commonly occurred around the Italian city of Taranto. Because of the large size (1 inch is large for a European spider) this species was greatly feared. During the Middle Ages it was believed that if someone was bitten by this spider the only cure was for the patient to dance wildly until he or she fell down out of exhaustion. As a result a very vigorous dance in the region was given the name tarantella. In addition a group of musicians traveled around the countryside that was more than willing to assist in treatment of spider bites. It is now documented that the fear of this original tarantula was unfounded since the bite of this spider is no worse than a bee sting.

It is probably not a good idea to handle a pet tarantula as these are basically wild animals and can be unpredictable in behavior. A case in point was recently demonstrated with my wife (Pat) and coauthor of this text. She used to do classroom presentations and frequently used a rather docile species of tarantula to show the kids. Unfortunately one day she accidentally dropped the critter. Well tarantulas are rather heavy bodied and do not fall well. If the exoskeleton of a tarantula is cracked the animal will usually bleed to death as its blood flows freely within the body and is not contained in vessels. Needless to say the tarantula died. By the way I recently learned that if you drop your tarantula and crack its exoskeleton without causing internal damage, superglue can be use to seal the crack and save the spider. Anyway we were looking for a replacement and someone gave me a Chilean rose haired tarantula which has a reputation of being very docile. Well Pat asked me to hand her the tarantula but once placed on her hand it sunk its fangs into her thumb. She was quite calm about it and merely stated “I think you should remove the spider as it is biting me”. I had told Pat that the bite of a tarantula is no worse than a bee sting which is true but I did not tell her that we didn’t know a lot about the effects of the venom of all tarantulas. She actually did have some unusual effects. One of her arms went numb which subsequently progressed to her back and across to the other arm. Even today she has 2 small pits in her thumb as a result of the spider’s injected venom in an attempt to digest her (see external digestion).

Tarantulas are long lived. The females of some species can live upwards of 20 or more years. On the other hand the males rarely live over a few years. Part of the reason for this is that males reach sexual maturity within 3 to 4 years on an average. At that point they search for a female and if successful are consumed by their mate after mating. If they escape from the female they soon die as their biological function is finished. It is thought that the male may actually hang around after mating and make no attempt to escape. This is advantageous to the species as the female has a tasty meal in preparation to egg production. Male tarantulas differ structurally from females in that their bodies are less bulky with long legs; many have bulblike structures on the tip of their pedipalps for sperm transfer. Hooks on some male's front legs are used to hold the female's fangs so she can't eat him during mating.

Figure 4J. A nicely marked species of South American tarantula 
Figure 4J. A nicely marked species of South American tarantula 
Figure 4K. The chelicerae or fangs of an average sized tarantula. 
Figure 4K. The chelicerae or fangs of an average sized tarantula.

Besides biting, New World tarantulas frequently protect themselves by kicking off puffs of branched body hairs from the back of their abdomens with their hind legs (Figure 4L). The mucous membrane of the eyes and nose of mammals, including humans, are quite sensitive to these hairs and resultant watery eyes and severe itching of the skin may last for several hours. These hairs can penetrate the skin up to 1/16 inch and frequently have a toxin associated with them. People who handle tarantulas may develop an allergic reaction to this venom, causing increased sensitivity and irritation after minimal contact. Because the venom in the hairs is likely to be the same as that in the fangs, someone who has developed sensitivity to the hairs could have a more severe reaction upon being bitten. The hairs are regenerated each time the tarantula molts.

Figure 4L. A South American goliath tarantula with balding abdomen due to defensive kicking of hairs.
Figure 4L. A South American goliath tarantula with balding abdomen due to defensive kicking of hairs.

Most tarantulas in the United States feed on insects and, possibly young rodents. There are a number of tropical species that live in trees (arboreal) and possibly feed on young birds (the bird spiders). Many of the bird spiders are relatively slender bodied and exceedingly hairy with long hairs extending at right angles from the body. The authors were not sure of the function of these hairs until one day we accidentally dropped a rather hairy one. While in midair, the spider extended its legs in all directions and floated to the ground--much like a falling leaf. The long hairs obviously increased the surface area of the spider, which along with the spider's relatively light body, allowed it to perform this acrobatic feat--a behavior that obviously has advantages when living in trees. The main diet of bird spiders is not birds but insects.

The Mexican red-knee (Figure 4M) is one of the most brightly colored and docile tarantulas known. This species was collected by the thousands from Southern Mexico and imported for years into the United States for the pet trade. Several years ago the Mexican government prohibited this practice due to the depletion of the species. Mexican red-kneed tarantulas occasionally can still be found in pet stores but these come from tarantula breeders. They are typically available as tiny spiderlings.

The importation and exportation of animals and plants and/or their parts (e.g., Mexican red-knee, animal horns, and spotted cats) in many countries throughout the world has become a major problem. As a result, a number of these countries have formed an international agreement called the Cites Agreement. . Each country has identified the plants and animals (including their parts) which they want to protect. Once placed on a CITES list, an organism cannot be exported from a country without a permit from that country. In many cases these permits are not available. In the United States, the Fish and Wildlife Services enforces this agreement. If they catch someone exporting or importing an illegal CITES organism, the penalties can be quite severe. An individual recently was caught bringing into the U.S about 80 Mexican red-knee tarantulas. He was sentenced to 6 years in jail.

In the news today (August, 06) there was a case where an individual was caught trying to import a number of illegal butterflies (CITES ) including 2 Queen Alexander birdwings-largest butterflies in the world-valued at $8500 each. He was indicted on 15 Federal charges as a result of a 3-year investigation by the Federal Fish and Wild Life Services. This individual was a fairly well-known insect dealer.

Figure 4M. A female red knee tarantula. 
Figure 4M. A female red knee tarantula.

The authors were somewhat skeptical about reports of a few incidences where a tarantula attempted to heal its own wounds with its webbing. However, one day we were closing the cage door of a Chilean rose-haired tarantula and accidentally chopped off part of its leg. As blood began to ooze from the wound the tarantula spun several strands of silk and wrapped it around the wound, thus effectively sealing it. Without this tourniquet the tarantula would likely have bled to death. The Chilean rose-haired tarantula (Figure 4N) is the most common species sold in pet stores. They tend to be quite docile and in most cases are reluctant to bite.

Figure 4N. A Chilean rose-haired tarantula-the most common species available inpet stores. 
Figure 4N. A Chilean rose-haired tarantula-the most common species available in pet stores.

The goliath spider from South America (Figure 4O) is the largest species of spider in the world. A large specimen with its legs fully spread will exceed the size of a dinner plate (10 inches). Some of these giants of South America feed almost exclusively on lizards, frogs and snakes. This spider is commonly referred to as a bird eater. This is a misnomer as these ground inhabiting, heavy bodied spiders are rather slow moving and can not climb all characteristic which would be detrimental to catching birds. Apparently this name was probably acquired because one of the original books published about spiders had a drawing of this spider sitting next to a dead bird. When given a choice this tarantula prefers the cold-blooded vertebrates to insects. Some of the more primitive human tribes actively seek these giant tarantulas of the rainforest as a food source; the spiders are roasted to remove the body hair. The eggs of a gravid female are a special treat making a nice omelet! Tarantula is said to taste like chicken; actually, it has a distinctive flavor of its own-I guess.

On one occasion we received a live adult female goliath spider. As one of my colleagues and I were observing the spider, I asked him, "Do you want to hold it?" He responded rather abruptly, "No!" I replied, "Me neither, let's feed it." It was a real monster, with at least one-inch long curved fangs. So we proceeded to throw a large mouse in its cage. The spider immediately jumped on the mouse and began pumping in salivary enzymes with its needle shaped fangs. Upon our return the next day, there was nothing left but a small ball of fur. The tarantula had consumed, everything else including the bones. We never handled that one-Ever.

 
Figure 4O. A Goliath spider-one of the largest tarantulas in the world.

OTHER SPIDERS THAT OCCASIONALLY BITE

All spiders have fangs and poison glands (there are a few exceptions); however, many are timid and will not or cannot penetrate the skin because their fangs are too small. There is a tremendous lack of knowledge about the effect of the bite of many common spiders in the world. A good example of this is the brown recluse. As mentioned above, the spider experts strongly feel that this spider no longer exists in California. However, as with many other hospitals, Redlands Community (a Southern California hospital) reports treating several brown recluse bites a year. If the spider experts are correct, there must other species of which we are not aware, whose bite produces symptoms similar to that of the brown recluse.

Grass Spider
The grass spider (Figure 4P) is a common species that reportedly occasionally bites humans. Adults are a little less than ½-inch in length with 2 dark parallel stripes running the length of the cephalothorax. The overall body color is tan with mottled white markings. This spider inhabits gardens and junk piles and lives under stones and logs. The web is trampoline-like in shape and tapers back into a funnel where the spider hides and waits for its prey. This species can produce a painful bite due to its powerful jaw muscles and large fangs. The nature of the venom is unknown. Typically a bite will cause mild swelling and a red spot. There have been some recorded cases of more severe symptoms which could possibly be due to allergic reactions to the venom or a secondary infection.

Figure 4P. A grass spider may bite resulting in mild swelling. 
Figure 4P. A grass spider may bite resulting in mild swelling.

Green Lynx Spider
Adults of the green lynx spiders (Figure 4Q) are about 3/4 inch long and apple green in color with long spindly legs covered with black spots. This species is found in gardens, tall grass, chaparral, on flower heads and bushes. It hunts and captures it prey without the use of a web. The green lynx fiercely guards its egg sac and is capable of biting and spitting its venom a distance of a few inches. The venom may cause eye irritation that will clear up in a few days.

Figure 4Q. The green lynx spider is capable of spitting its venom a few inches.Image courtesy of Russ Otten, Univ Geroria, Bugwood.
Figure 4Q. The green lynx spider is capable of spitting its venom a few inches. Image courtesy of Russ Otten, Univ Geroria, Bugwood.

SPIDERS THAT RARELY OR NEVER OR CAN’T BITE

Orb Web Spiders
These are some of the most obvious outdoor spiders. In the US these spiders are also called "garden spiders.” They are large, often brightly colored spiders (Figure 4R) that make large webs in locations that are readily visible. An orb web is the stereotypical web that most people think of when they think of a spider web. It basically consists of 25 to 30 radial fibers that are connected by a number of spiraling or circular fibers. The spiral fibers are coated with a thin layer of sticky material that under tension breaks up into tiny globules. These are the fibers that trap the spider’s prey. The question may arise why does a spider not get trapped in its own web? One reason is that when traveling over its web it moves primarily over the radial fibers avoiding the sticky material on the spiral fibers. In addition their legs are coated with an oily material that repels the sticky substance.

 
Figure 4R. Orb web spiders. Top right and bottom images courtesy Peter Chew, Brisbane Insects.

This spider can be identified by the construction of its web. It is the only spider that makes a zigzag line or a cross of zigzag white material in the web (Figure 4S). The exact function of these lines is not known; however several have been suggested. The spider hangs head down, in the hub. When stimulated the spider vibrates its web vigorously until it becomes an indistinct blur. The combined zigzag structure and indistinct appearance are thought to possible increase overall apparent size of the spider making it less attractive to potential predators. This vibrating also possibly makes the spider a less precise target to a potential predator. More recently it has been found that in some spiders these structures reflect ultra violet light. It is well known that many flowers also reflect ultra violet light which functions as guides leading to their nectar-producing glands. As a result it has been suggested that instead of functioning as a protective device against predators the stabilmentum serves to attract nectar seeking insect to the spider’s web.

Figure 4S. Orb web with stabilimentum. Images courtesy Peter Chew, Brisbane Insects. 
Figure 4S. Orb web with stabilimentum. Images courtesy Peter Chew, Brisbane Insects.

Water Spiders
spider as their name implies are commonly found around slow moving streams or lakes, They are typically long legged Figure (4T) and are capable of rapidly running over the surface of water. Their long legs that are covered with non-wettable hairs or setae and light body allows them to accomplish this task. They either feed on terrestrial insects or are capable of diving below surface to catch aquatic insects, tadpoles or small fish. Some species will actually dip or tangle a leg into the water which is thought to either attract the above or possibly detect subsurface movement by a potential prey.

Figure 4T Common water spider. 
Figure 4T Common water spider.

Daddy-Longleg Spiders
These spiders have very long legs and look similar to the harvestmen or true daddy longlegs. The harvestmen are not true spiders and actually belong to a separate order (Phalangida), as discussed earlier. The members of the daddy-longlegs spiders (Figure 4U) are the most common spiders that are found in houses and buildings. They normally make their webs in the corner of a wall or ceilings but in warm climates are also very commonly found under the eaves of homes and porch overhangs. Another common location is in basements or cellars, thus being referred to as the cellar spiders. My wife really like spiders and doesn’t want me killing these spiders that inhabit our house. Consequently we don’t have to decorate that much for Halloween. When it gets really bad I sometimes sneak out with the vacuum at night. When disturbed or under threat of attack, they violently vibrate their web in attempt to discourage the intruder, hence another common name of the vibrating spiders. Some indications are that this spider has very toxic venom; however, their fangs are too small to penetrate the skin and are not considered dangerous. (Pat’s note: Dick doesn’t know it, but I go back out and sneak them back in after he goes to sleep.) (Dick’s note. I do now!)

These 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. The main webbing is relatively weak and typically is not used to trap prey and is primarily used for retreat. Likewise their chelicerae are also too small to hold prey. This spider traps its prey by throwing tough, stiff web material over the victim. After the prey is motionless, it is wrapped and subsequently pumped full of digestive enzymes. These spiders are capable of subduing almost any type of arthropod including larger wolf spiders, black widows and even other daddy longlegs. Even though the average homeowner is unwilling to put up with them, these spiders are quite effective predators and can significantly reduce the presence of other bugs in the home.

In the winter when the general insect population is at its lowest, the spider moves through the house on hunting expeditions. On such occasions it even starts looking for the web of other species of spiders. If found it will vibrate the web (simulating a captured prey) in combination with acting like a captured prey-this behavior includes twitching its abdomen, bouncing in place and shivering and tensing while contracting its legs toward its body. All these behaviors tend to excite the other spider which emerges expecting a capture prey but is consumed by the larger long-legged cellar spider.

Figure 4U. Daddy-longleg spider. 
Figure 4U. Daddy-longleg spider.

This species originally came from the tropics and in colder climates is found only inside houses. Unlike most other spiders, daddy longlegs breed throughout the year. The fertilized eggs are not spun in a cocoon, but are held in a small net of silk. Because the spider is always on the move, it is common to see a female carrying her sac of 20 to 30 eggs with her.

Wolf Spiders
These spiders are real hunters and because they depend on vision to catch their prey, they have excellent eyesight with 8 well-developed eyes (Figure 4V). Four small ones are located at the lower part of the front of the cephalothorax. Immediately above these there are 2 large eyes that face forward and farther back there are 2 large eyes that are directed upward. In this way the spider can look in 4 directions and can perceive a moving insect at a distance of several inches.

These are relatively large spiders with elongated legs, an adaptation for fast movement that is needed to run down their prey. These spiders vigorously attack their prey crushing them with their well-developed chelicerae. Their name "wolf spider" is derived from the fact that people erroneously thought they hunted in groups like wolves. These spiders live in every variety of terrestrial habitats. They have been found skating over water and even diving under the surface, catching small fish and insects. Some species fish by placing and wiggling one of their legs in water and if a fish is attracted, expecting to catch a meal, the spider quickly attacks.

As with many species wolf spiders have strange and often unique mating behaviors. When a female is ready to mate she will construct a small silk-lined-cavity. A male can actually locate a receptive female by the smell of this fresh silk. This is especially important because if he approaches a female that is not ready to mate she will likely eat him. Even if she is receptive he needs to signal her of his intentions. Males of different species accomplish in a variety of ways. Some species use sound: one mere taps his leg on the ground while another rubs roughened areas on opposing palps producing a buzzing sound –much like a doorbell! Others rely on sight since these spiders are provided with excellent eyesight (at least in the spider world). In this case the male’s palps are fringed with bright color or band of black hairs. The expectant male approaches the female wildly waving his palps signaling-I’m good!-I’m’ ready!-Don’t Eat Me! Finally there is a species that attempts to win a mate favor by bearing a gift. He catches an insect, carefully wraps it in silk and then carries it in his jaws to a receptive female. Once within striking distance he extends his front leg (almost looking like a bow) making the gift very evident and well placed between his and her jaws. If she accepts the gift by grasping it with her jaws he quickly maneuvers to a mating position.

Unlike most other spiders, the majority of the wolf spider species show a degree of maternal instinct by carrying their egg sacs attached to the underside of the abdomen. Once hatched the spiderlings crawl on the back of the abdomen until the first molt. During that time the mother will engage her normal hunting activities with her young tightly attached to her body. When the young are brushed from her body they will crawl back very quickly. During the time the young are attached at the body of their mother they do not eat living off of stored nutrients in the bodies but do drink water from morning dew.

 
Figure 4V. Wolf spiders with (left) carrying young on abdomen. Left image courtesy of Peter Chew, Brisbane Insects.

She is very protective of both the eggs and young spiderlings and will readily attack any threatening intruder. It should be mentioned that maternal instinct in arthropods in general is merely a thoughtless mechanical response to external stimuli. If the egg sac of a wolf spider is removed and replaced with a piece of cork, the female will also protect the cork with her life-no thought processes here

Jumping Spiders
These are some of the most readily recognized and common spiders found in the US as well as in the tropical areas of the world (over 4,000 species worldwide). They are readily recognized by their distinctive shape and ability to jump. These spiders are capable of jumping over 40 times their length. This is equivalent to a 6 foot man jumping 240 feet. Whenever we go to elementary schools to give a presentation and show a slide of a jumping spider, most of the kids already know exactly what it is.

An additional distinctive characteristic is their large eyes (Figure 4W). These spiders have the best-developed visual system of all spiders, which is used to best advantage when hunting prey. As do most spiders, they have 4 pairs of eyes. One large pair and 1 small pair are oriented in a forward facing position. Above this front row is a second row of 2 tiny eyes and behind these there is a set of 2 large eyes oriented in an upward position. As a result these spiders can see in a 360-degree plane. Unlike other spiders they can move their eyes outward or inwards for focusing and they can be turned up and down and from left and right. The spider can also turn its carapace (breast) more than 45 degrees to look around.

 
Figure 4W. Jumping spiders with well-developed eyes. Images courtesy Peter Chew, Brisbane Insects.

Prey can be distinguished from a distance of about 30-40 cm. Experiments have indicated that they are capable of distinguishing dangerous insects from prey. As their name implies, jumping spiders do not use webbing to capture their prey. Anyone who has ever watched these tigers of the spider world stalk their prey is truly amazed. They typically edge up until they are within an inch or so of the prey and then pounce. They are capable of subduing prey that is many times their size. When one of these spiders jumps, it simultaneously releases a silken lifeline. If the jump fails it can then crawl back to its original position. As indicated jumping spiders do not make webs to catch prey. However, they do make a retreat of thick, white, slightly viscous silk which typically occurs in crevices, under stones on the ground and similar situations.

These spiders live for the most part on vegetation. However, some species exhibit an amazing resemblance to ants and are called ant-like spiders. The obvious advantage of this is that they can intermingle with and feed on ants without being detected. In some cases, they have been shown to travel on the same trails with certain species of foraging ants.

Crab Spiders
This is a large family with more than 3000 known species. They can be readily recognized by their behavior and overall appearance. They are named after the behavior of moving sideways (like a crab) when disturbed. Crab spiders are frequently brightly colored with a pancake-shaped abdomen and stout cephalothorax (Figure 4X). The front 2 legs, which are often larger and stronger than the other 6, are held sideways in an open position ready to catch the prey. Their eyesight is excellent with 2 big front eyes. Sexual dimorphism, or when the male and female of a species appear distinctly different, is quite distinct in many species of crab spiders.

Figure 4X. Crab spider in typical ambush position 
Figure 4X. Crab spider in typical ambush position

They are not active hunters and typically lie in wait for approaching meals. Favorite waiting locations include flower heads and leaves. In the case of flower heads, they mainly feed on those insects that come for the pollen and nectar. In most cases crab spiders sit on flowers of their same or similar color, relying on camouflage and the advantage of surprise. A few species can actually change their color to the surrounding environment, although unlike some other animals, this takes a few days. They remain motionless until an insect arrives and then subdue it with their legs and fangs. Often the crab spider remains for days, even weeks at the same spot.

Trap Door Spiders
These relatively large spiders (adults reaching 2.5 to 3.5 cm in length) are rarely seen as they spend the majority of their lives in well-designed tunnels in the ground (Figure 4Y). The only time that a trap door spider is commonly seen is when the male reaches sexual maturity and strikes out in search of a female. Otherwise they remain, grow and molt inside their tunnels. The entrance of the tunnel is typically covered by an earthen door that is hinged at one end. The door is extremely difficult to spot as it blends in with the surrounding environment.

 Figure 4Y. A trap door spider. 
Figure 4Y. A trap door spider.

Trap door spiders do not leave their burrows to hunt but merely wait with the door partially open for passing prey. Their eyesight is not well developed and they rely on sensitive hairs on their legs to pick up the vibrations of a passing prey. Some species actually place elongated twig or silken strands (Figure 4Z) radiating out from the entrance to increase the distance of detection from the entrance.

 
Figure Z. The door of a trap door spider with silken stands and twigs radiating outward to detect potential prey.

The burrow and door serve not only as a home and means to capture prey, but also protects the spiders from rain, regulates the humidity and temperature, and helps protect them from potential predators, such as centipedes, scorpions and parasitic wasps. In some species the spider has a set of spines on its legs, which it presses into the side of the burrow while it holds the door shut with its fangs. We once tried to pry open the door of one of these spiders with a spoon and actually bent the handle in doing so. It is now known that this spider can withstand the pull of 38 times its weight.

Some species store the remains of their prey and other debris behind the silk lining of the tunnel. If a potential predator breaks into the tunnel, the spider will rush to the bottom of the tunnel while simultaneously releasing the debris and silk lining, thus forming a false bottom to the tunnel and concealing the spider beneath.

TROPICAL SPIDERS OF INTEREST

Golden Web Spiders
Anyone who has been in the tropics (east and west) has undoubtedly come across the golden web spiders in the genus Nephila (Figure AA). These are beautiful monsters. The adult females of some species can reach a body length of 2-½ with a leg span of 8 inches. They are quite beautiful with many iridescent colors. In comparison to the females, the males are minute, in some species 1,000 times smaller than the female (Image 4X). The males are normally found in the same web as the female, but are not in danger of being eaten because they are so small that the female does not recognize them as food.

 
Figure AA. A typical (Thai) golden orb web spider. The web of this spider is so strong that it can trap birds and bats. Note small male in right image (top-middle). Right image courtesy of Peter Chew, Brisbane Insects.

As amazing as are these spider, their web is even more impressive. The silk itself is a golden color and quite strong. The silk is so strong that birds, bats and lizards are frequently trapped and consumed. The webs themselves are large, with the central hub of the web reaching 6 to 7 feet in diameter width and the radiating supporting strands attach as much as 20 feet apart. The webs are so extensive that these spiders typically do not make new webs but continuously repair the old one. The webbing of these spiders is so strong that the natives in some of the Pacific island use it for fishing line.

As impressive as these spiders are they are not impervious to competition or even predation from other spiders. On one of our student trips to Thailand I was walking along a trail in the mountains and came across a large female Nephila spider that had recently caught and was feeding on a small bird. I noticed that there were 2 other spiders (about 1/20th her size) feeding on the same bird. Apparently there are a number of other spiders that “pirate” feed on the prey of this species. Argyrodes, a close relative of the black widow, is one of the main spiders that exhibits this behavior. This spider typically builds its web close to that of the golden web spiders but makes frequent excursions onto the web of the giant. Once this pirate determines that Nephila has made a catch it waits until the prey is subdued, tightly wrapped with the giants silk and moved to a storage location on the web. At that point Argyrodes carefully moves toward the prey avoiding vibrating her web so not to end up as desert. Once locating the prey Argyrodes cuts the filaments that support the wrapped package and steals away with its prize. The orb spider’s web is so large that it is not uncommon for up to 40 of these pirates to feed off its catch. If pickings are slime these pirates on occasion will attack, subdue and eat the orb spider.

Banana or Huntsman Spiders
This is a group of rather large (1-inch body length) tropical spiders that are worldwide in distribution (Figure 4BB). They got the name “banana spiders” because they are commonly found in bunches of bananas and are consequently shipped around the world. Most produce managers of grocery stores are familiar with these spiders. They are quite docile and we understand that this was the main spider that was used in producing the movie Arachnophobia.

Figure 4BB. Giant huntsman or banana spider 
Figure 4BB. Giant huntsman or banana spider

 

Bolas Spiders
This group of spiders (Figure 4CC) has a rather unique means of catching their prey. They are part of a tribe of the orb-weaving spider family (Araneidae) that no longer build an orb web, but instead attract their prey (male moths) by chemical mimicry. The moths are captured using a "bolas" which is a sticky ball of glue attached to a strand of silk (Figure 4DD). The spider swings this around until the ball hits and sticks to the approaching moth. The moth is then reeled in by the spider and wrapped in silk. This would be a pretty inefficient means of capturing prey if done at random. The chance of catching a moth that merely flew by would be pretty remote. However, the spider actually emits a sex pheromone that mimics that produced by female moths to attract males for mating. Instead of finding a mate the males end up as dinner for the bolas spider. Even more amazing this spider feeds on 2 different species of moths each of which fly and typically mate at different times of the night-one early in the evening and the other late at night. Accordingly the bolas spider produces and releases 2 different pheromones each at the correct time that correspond to when each species flies.

 Figure 4CC. An Australian female bolas spider. Image courtesy of Dave Britton. 
Figure 4CC. An Australian female bolas spider. Image courtesy of Dave Britton. 
 Figure 4DD.  A bolas spider swinging its sticky ball.  Image courtesy of Dave Britton. 
Figure 4DD. A bolas spider swinging its sticky ball. Image courtesy of Dave Britton.

An equally amazing feature of this spider is the huge size of their egg sacs. Typically several (Figure 4EE) of these giant are produced by the female. It is thought that she is capable of doing this due to the small amount of silk used in catching her prey.

Figure 4EE. A female bolas spider sitting on one of its several egg masses. Image courtesy of Dave Britton. 
Figure 4EE. A female bolas spider sitting on one of its several egg masses. Image courtesy of Dave Britton.

Web Casting Spiders
These spiders have a unique means of capturing their prey. In this case they use a preformed web, much like a fish-net. The spider typically builds the web over an area that is frequented by insects such as a broad leaf, downed tree trunk or wall. The net is not sticky but are quite flexible and can be expanded to 5 times its smallest size (Figure 4FF). Once the spider forms the net it move to the desired position with its suspend with a safety line head facing downward and holds the 4 corners of the net with its 4 front legs. It simultaneous holds a safety line with its last pair of legs. When a prey passes under the spider jumps down by cutting the safety line and simultaneous releasing the expanded tension of the net. The net contract and entangles the prey. Some species mark the desired target area (e.g. on a leaf below the waiting spider) with white spots. It is thought these serve to indicate the prey is in a good location for capture.

A web casting spider with net in relaxed condition. Image courtesy of Peter Chew,Brisbane Insects in. 
A web casting spider with net in relaxed condition. Image courtesy of Peter Chew, Brisbane Insects in.

SPIDER MYTHOLOGY

Because these critters are some of the larger and most commonly encountered arthropods on the planet, it follows that there is considerable myths and falsehoods associated with them. One very common belief in many parts of Central and South America is that when a spider urinates on a horse, its hoof will fall off. In such regions, children are given the task of collecting and killing all spiders around horse corrals. In actuality, horse's hooves are susceptible to splitting and even "falling off," which in extreme cases leaves the animal lame for life. This phenomenon is referred to as "founder," but is by no means due to spider pee, as spiders do not pee and in most cases their feces is quite dry. Keep in mind that one of the main physiological battles of these creatures is the loss of water and any excess water in the feces would be adding to this problem. Founder can result from any extreme tissue damage occurring on any part of the body. If this occurs, chemical messages are produced that cause the blood vessels in the hoof (and other parts of the body) to constrict, resulting in splitting of the hoof. It is possible that if a horse were to be bitten by a very toxic spider (which could cause tissue damage), founder might occur.

Spiders, in general, have been the stuff of legends in many cultures. Sometimes demonic, sometimes altruistic, always cunning, they are usually portrayed as extremely clever animals. In various accounts, spiders have been attributed to be heroes by saving or inspiring important religious or political figures, such as Mohammed, Robert the Bruce or Yoritomo. Mohammed and Yoritomo (a Japanese hero of the twelfth century) were both said to be concealed from harm by the huge web of a spider. Robert the Bruce was inspired by the perseverance of a spider as she tried and tried again to spin her web as he hid from battle. The story goes that her heroic measures gave him the strength to go back into the fray and save Scotland.

In some American Indian cultures, Spider Woman is a cautionary figure used by mothers to warn unruly children. Spider Woman is a protector to the Navajo. She instills a type of spiritual protection and, as a creator, a love of beauty. The comparison of an intricate and elaborate orb web to a beautiful tapestry is not hard to make. Spider Woman, being a spinner, is represented by a tiny hole found in all traditional Navaho blankets that indicates the spot where she can escape.

Gaia culture portrays the spider as a sort of earth goddess, a spinner of life and death: a positive figure. The Greco-Romans put a far darker slant to this deft weaver known as Arachne. She is turned into a spider by Athena, the Goddess of Crafts. The story goes that after a contest of skillful weaving, Athena is enraged by the subject of Arachne's tapestry—a portrayal of the gods, especially Zeus (highest god of all and Athena's father), in an unflattering light. After condemning her to hang until dead, Athena spared her life but turned her into a spider—dangling from a web instead of a noose. Arachne is the reason that spiders are known as Arachnids.

Tarantulas are hairy behemoths of the American spider world. In southern Italy, the name "tarantula" came into usage in the town of Taranto. A local large wolf spider was considered to be extremely venomous. The legend was that if this spider bit someone, they must begin dancing to a lively song known as the tarantella or they would fall into a coma. The spider became known as "tarantula." This particular spider is not really very venomous and the others we know as tarantulas usually aren't either. But their size alone is enough to give some people nightmares.