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This introduction to the diverse yet little known world of spiders is packed with concise, accurate information. With full-color pictures and readable text, this guide identifies representative species and describes:
Their characteristics and habits
Growth, courtship and enemies
Where they are found
Includes information on poisonous species and how to collect, preserve, and raise spiders.
About the Author
Golden Guides first appeared in 1949 and quickly established themselves as authorities on subjects from Natural History to Science. Relaunched in 2000, Golden Guides from St. Martin's Press feature modern, new covers as part of a multi-year, million-dollar program to revise, update, and expand the complete line of guides for a new generation of students.
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SPIDERS AND THEIR KIN
About 35,000 species of spiders have been named so far, representing what is believed to be about one-fifth the total. Some 3,000 kinds are known from Europe; 3,500 from less-studied N.A. The 700 species of spiders found in New York and New England about equals the species of birds breeding in N.A. north of Mexico.
Spiders are members of the phylum Arthropoda, the large group of animals with jointed legs and a hard outer skeleton. They belong, more specifically, to the class Arachnida, which includes animals with four pairs of legs, no antennae or wings, and only two body regions — a cephalothorax and an abdomen. Arachnids and two smaller marine arthropod groups form the subphylum Chelicerata. These arthropods all possess chelicerate jaws which sometimes are modified into pincers as in windscorpions or into piercing stylets, as in some mites.
All other arthropods have antennae and mandibles that work against each other. They are placed in six classes. These include the insects (class Insecta), which have three body regions, three pairs of legs, one pair of antennae, and often wings; the crustaceans (class Crustacea), mainly water-dwellers — the crabs, lobsters, shrimp, barnacles, and water fleas; and the myriapods: centipedes (class Chilopoda) and millipedes (class Diplopoda); and classes Symphyla and Pauropoda found in habitats like those of spiders.
In spiders, the abdomen is attached to the cephalothorax by a narrow stalk; in scorpions, harvestmen, and mites, the attachment is broad. Spiders usually have eight simple eyes, variously arranged, and some have acute vision. Scorpions have both median eyes and (usually) lateral eyes; harvestmen, only median eyes; pseudoscorpions, lateral eyes or none. Long setae (hairs), sensitive to vibration, air movements and sound, occur on the legs of some spiders and on the pedipalps of scorpions and pseudoscorpions.
In spiders the abdomen shows little or no segmentation, but segments are distinct in scorpions. The segmented spiders, suborder Mesothelae, family Liphistiidae (see here), are an exception. These spiders live in burrows in the soil and are only found in East Asia. In the other suborders of spiders, Mygalomorphaeand Araneomorphae, vestiges of the segmentation thought to characterize ancestral forms, is reflected externally by the pattern on the back of the abdomen and sometimes by the presence of several hard plates (sclerites); internally by the muscle arrangement and structure of the heart.
This book treats the land arthropods other than insects. Of these, the spiders and mites, both of the class Aarchnida, are the most abundant. Mites are mostly microscopic and difficult to study, hence are given little attention here.
ARTHROPODS evolved from marine segmented worms. Fossils do not reveal whether they evolved from different stocks or all from one group. Onychophorans, represented by the many-legged, soft-bodied Peripatus mainly of the Southern Hemisphere, are perhaps similar to some ancestor. The groups of arthropods and their probable relationships are shown above.
The most wormlike arthropods are certain centipedes that consist of series of similar segments. In other arthropods, groups of segments have become specialized. In insects, one group of segments forms the head; another, the thorax; a third, the abdomen.
Two marine groups related to the arachnids are included in the subphylum Chelicerata: horseshoe crabs, which live only on the east coasts of Asia and N.A.; and sea spiders, which are slow marine creatures that feed on hydroids, anemones and other sea animals.
THE SPIDER'S BODY consists of a cephalothorax, covered by a carapace (shield), and an abdomen. Four pairs of legs are attached to the cephalothorax. The legs end in either two or three claws, varying with the family. Nearly all spiders have eight simple eyes. Their arrangement, important in identifying families, is shown in black-and-white diagrams with family descriptions. The shape of the carapace is commonly distinctive, too.
The cephalothorax (combined head and thorax) contains the brain, venom glands (see here), and stomach. In the abdomen (see here) are the heart, digestive tract, reproductive organs, lungs and respiratory tracheae, and silk glands. The two parts are connected by a thin stalk, the pedicel, through which pass the aorta, intestine, nerve cord, and some muscles. Spinnerets (usually six) issue strands of silk through tiny spigots. Between the front pair in some spiders is the colulus, its function unknown. In cribellate spiders, the cribellum is here.
THE JAWS, or chelicerae, open forward inMygalomorphae and in the Mesothelae (see here), and to the sides in other spiders. Spider jaws are tipped by fangs, with a duct from a venom gland opening at the end of each. In front of the labium (lower lip) is the mouth, its opening covered by the labrum (upper lip).
Spiders feed on living prey, which may be paralyzed or killed with venom. Juices from the digestive glands liquefy the prey before it is sucked into the mouth by the stomach's pumping action. Spiders with few teeth on their jaws may suck out the insides of prey and discard the empty shell.
PEDIPALPS, between the jaws and the first legs, are small and leglike in females and in young spiders. In males, the tip is enlarged. Before searching for a female, the male deposits a drop of sperm on a special web, then draws it into the palp.
In mating, the sperm is transferred by inserting the palp into an opening on the underside of the female's abdomen. In most spiders, this opening is on a hard plate, the epigynum, just in front of a slit (gonopore) through which the eggs pass. Some, called haplogyne spiders (see here), lack an epigynum; the palpus is inserted directly into the gonopore.
EXTERNAL FEATURES shown below are used in the text to describe families and species.
Measurements given in this book are of the adult spider's approximate body length, excluding legs and jaws. They are not measurements of leg span. All spiders show individual and regional differences in size. The sign is used for female, for male.
COURTSHIP by the adult male begins after his palp is filled with sperm (see here) and he has found a female.
Some hunting spiders locate mates by finding and following the draglines laid down by mature females of the same species. Experiments have demonstrated that male web spiders can often tell by touching the web whether it contains a mature female. Male orb weavers and other web spiders with poor vision announce their approach by plucking the strands of the female's web. Others stroke and tap the female cautiously. Spiders with good vision, such as wolf spiders (below) and the brightly colored jumping spiders, dance and wave their legs before their mates. A nursery web spider presents his mate with a fly before mating.
A female does not ordinarily feast on her mate, as many people believe, but males usually die soon after mating. Some male and female sheet web spiders live together in the same web.
After a week or more, the mated female deposits her eggs in a silken sac. Some species make several egg sacs, each containing several hundred eggs. Species that take care of their eggs or young usually produce fewer eggs. Weeks later, or sometimes not until the following spring, the young spiderlings emerge.
GROWTH of a spider requires shedding its exoskeleton, usually 4 to 12 times before maturity. Femalemygalomorph spiders continue to molt once or twice a year through their long adult lives.
Before a spider sheds, the inside layers of its skeleton are digested. The remaining skeleton then tears more easily. As molting begins, increased blood pressure causes the skeleton to tear at the front edge, continuing around the carapace, which then lifts off; the skin of the abdomen splits. A pumping motion lowers and raises leg spines, making the old skin slip over the flexible new legs. In the process of molting, a previously lost leg may be replaced by a new, smaller leg.
Most spiders live one or two seasons. Mygalomorphs do not mature for several years; the males live less than a year thereafter, but the females may live up to 20 years. Some primitive araneomorphs (such as Sicarius, Loxosceles, and Kukulcania) may live 5 to 10 years.
ENEMIES of spiders include other spiders (see here, and here) and some kinds of insects and birds. These enemies help to control spider populations, which are affected also by parasites and availability of food. The spiders in turn control to some degree the abundance of the prey they feed on, usually insects.
WASPS of some species prey only on spiders belonging to particular families or genera.
Below, a female wasp, Anoples fuscus, is stinging a wolf spider, Trochosa terricola (1). (Rarely the spider is the victor in these battles.) The wasp then carries the spider to her previously excavated burrow (2) and lays an egg on it (3). The wasp larva feeds on the paralyzed spider (4), eventually to pupate and metamorphose into an adult.
SILK produced by spiders is used in many ways (seehere). Pseudoscorpions, spider mites, most centipedes, and some millipedes also produce silk but only for mating or for egg and larval chambers. The caterpillars of many moths spin silk for their cocoons.
CHEMICALLY silk is a fibrous protein (fibroin), insoluble in water. It comes from spigots of the spinnerets in liquid form and hardens immediately, polymerizing as it is pulled out. Silk may stretch as much as one-fourth its length before breaking, and the silk of Nephila is the strongest natural fiber known. Spider silk is not used commercially, as the predatory habit of spiders makes it difficult to rear them in large numbers. Web spiders produce different types of silk from four to seven abdominal glands: viscid or sticky silk from some, web frame threads from others, egg sac silk from still others.
CLAWS on the tips of the legs are used by the spider to handle silk. The claws pivot back and forth, holding the silk between middle claw and two flexible setae (accessory claws). What prevents silk from sticking is not known. Spiders that build webs and walk on the silk threads have three claws on each leg. However, many hunting spiders have only two claws, for in place of the middle claw is a tuft of flattened hairs. Some also have a brush of hairs (scopula) under each leg's last segment. The claw tuft adheres to the water film covering most surfaces, permitting a spider to walk on smooth areas.
MANY USES OF SILK have evolved. Most spiders make silken egg cases, often spherical but sometimes flattened discs or stalked. Some species use silk to make anursery for spiderlings. Many hide in silk tunnels or use silk to line their burrows, or for trapdoors. Prey may be caught in webs, or snares, then wrapped (see here).
EGG SAC of Argiope bruennichi is shown below. The eggs are first stuck to a silk platform, then covered with threads. After they are wrapped in loose silk, a final cover of dense, colored silk is added. Argiope suspends the egg sac from vegetation.
BALLOONING spiderlings climb onto fence posts or branches and release silk. As the line lengthens, the wind lifts the little spider off its perch and floats it off to a new area. The masses of ballooning threads seen on fall days are called gossamer.
DRAGLINES of silk are laid down by most spiders. Fastened at intervals, they may serve as safely lines or to retrace a path.
SNARES of web spiders are a unique use of silk for trapping insects. Each kind has its special method of catching potential victims. Among them are cobwebs, sheet, funnel, and orb webs. Spiral silk in orbs is sticky in some, woolly in others (see here).
POISONOUS SPIDERS, specifically those dangerous to man, are few in number. In the United States and Canada, fatalities from wasp and bee stings far outnumber those from spider bites and scorpion stings. Few spiders will bite even when coaxed, and the bites of most of those large enough to penetrate the skin produce no harm at all.
Knowledge about spider venoms is very limited. Often a spider that bites is immediately destroyed or escapes. Even if the bite causes illness, the spider may not be positively identified.
In the U.S., the dangerous spiders include the Widows and the Recluse Spiders. Bites of Cheiracanthium, small whitish spiders found in most parts of the world, may produce a slight fever and destroy tissues around the bite. Venomous Hobo Spiders (Tegenaria agrestis) from Europe have been introduced to NW U.S. and Brit. Columbia. Their bites resemble those caused by Recluse Spiders. In Brazil Lycosa raptoria (see here) and Phoneutria are venomous. The Funnelweb Mygalomorph (Atrax) and a number of other Australian mygalomorphs have dangerous venoms.
WIDOWS are web spiders. The sedentary females may bite if molested. Males move about but do not bite. Widow spiders (see here) are found in most parts of the world. Species occur north to southern Canada and to southern S. A.
The bite may go unnoticed and may not hurt. But the subsequent severe abdominal pain from a Black Widow's bite resembles appendicitis. There is pain also in muscles and in the soles of the feet, but usually no swelling at the site of the bite. Alternately, the saliva flows freely, then the mouth is dry. The bite victim sweats profusely. The eyelids are swollen. The patient usually recovers after several days of agony. Physicians can relieve the severe pain by injection of calcium gluconate. Antivenin is available in all countries where bites occur frequently. No first aid treatment is available for any spider bite.
RECLUSE SPIDERS(Loxosceles laeta) of Chile, Peru, and Argentina have been known since the 1930's to cause severe illness. It was not until the 1950's, as a result of bites in Texas, Kansas, Missouri and Oklahoma, that the smaller Brown Recluse spider (L. recluso) was recognized to be similarly toxic. This spider commonly lives in houses on the floor or behind furniture. Bites occur when a spider rests in clothing or in a towel. There may be no harm at all. In very severe cases, a red zone appears around the bite, then a crust forms and falls off. The wound grows deeper and does not heal for several months.
Other species of Loxosceles are found in southwestern U.S. and in Mediterranean countries (see here). Probably because these spiders do not have contact with man, accidents do not occur. In any bite from a spider known to be poisonous it is wise to consult a physician as soon as signs of illness appear.
COLLECTING SPIDERS can be done nearly everywhere — in houses, gardens, fields and woods, under bark, stones, or logs. Turn stones and logs back so the habitat is not destroyed. Spiders that run along the ground can be chased into a glass vial or picked up and dropped into a vial of alcohol. Each collecting vial may be half-filled with specimens. Be sure to insert a penciled field label, citing locality, date, and collector.
SWEEPING shrubs and herbs with an insect net is a technique by which many spiders can be collected. Small spiders can be sifted from leaf litter by using a shaker with cloth sides and a 1 cm (¼?) screen bottom. Burrowing spiders must be dug out.
NIGHT COLLECTING with a miner's headlamp yields a harvest of wolf spiders, whose eyes reflect light, and of nocturnal orb weavers that show up against the dark background. Small spiders that hide in crevices by day sit in their webs at night.
A TIN CAN buried flush with the ground surface will trap running spiders. Put in the can a small amount of ethylene glycol (antifreeze), which does not evaporate. A raised lid supported by stones prevents dilution by rain. Empty once a week.
TULLGREN FUNNELS have a 1 cm (¼?) wire screen across the bottom. Leaf litter is placed on the screen. Fumes from a single mothball suspended below the lid will drive spiders and other small animals down into a container of water or alcohol below.
PRESERVATION of spiders and their kin must be in liquid, either 80% grain alcohol or 70–80% isopropyl (rubbing) alcohol, as these animals are soft-bodied and cannot be pinned and dried. In sorting, keep specimens submerged. Each labeled species should be kept in a separate vial and stored with others in a larger jar of alcohol.
Excerpted from "Spiders and Their Kin"
Copyright © 2002 St. Martin's Press.
Excerpted by permission of St. Martin's Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
SPIDERS AND THEIR KIN,
SPIDERS: 4 pairs of legs, spinnerets; cephalothorax and abdomen joined by narrow waist; no antennae,
Mygalomorph Spiders, Mygalomorphae: chelicerae (jaws) attached in front of head, open forward,
True Spiders, Araneomorphae: chelicerae attached below head, open to sides,
Cribellate Spiders: cribellum, a plate with spigots, in front of spinnerets,
SPIDER RELATIVES: no antennae, no spinnerets on posterior of abdomen; 4 pairs of legs,
Whipscorpions: strong palps, long whiplike first legs,
Windscorpions: huge jaws, leglike palps.,
Pseudoscorpions: large pincer-like palps, lacks stinger.,
Scorpions: large pincer-like palps, slender tail, with stinger,
Harvestmen: compact body, segmented abdomen, eyes usually on a tubercle.,
Mites: small, body compact, abdomen usually unsegmented,
Microwhipscorpions: small, leglike palps, long tail,
Ricinuleids: hood covers jaws,
MYRIAPODS: 1 pair of antennae, legs on a series of similar rings,
Pauropods and Symphyla: 9–12 pairs of legs,
Centipedes: 15 or more pairs of legs, one on each segment,
Millipedes: two pairs of legs on most body rings,
LAND CRUSTACEANS: two pairs of antennae,
Wood Lice: flattened, lack carapace,
Land Crabs: not flattened, cephalothorax with carapace,
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