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Field Guide to the Spiders of California and the Pacific Coast States

Richard J. Adams (Author), Timothy D. Manolis (Illustrator)

Available worldwide

Paperback, 452 pages
ISBN: 9780520276611
January 2014
$26.95, £19.95
Other Formats Available:
With over 40,000 described species, spiders have adapted to nearly every terrestrial environment across the globe. Over half of the world’s spider families live within the three contiguous Pacific Coast states—not surprising considering the wide variety of habitats, from mountain meadows and desert dunes to redwood forests and massive urban centers. This beautifully illustrated, accessible guide covers all of the families and many of the genera found along the Pacific Coast, including introduced species and common garden spiders. The author provides readers with tools for identifying many of the region’s spiders to family, and when possible, genus and species. He discusses taxonomy, distribution, and natural history as well as what is known of the habits of the spiders, the characters of families, and references to taxonomic revisions of the pertinent genera. Full-color plates for each family bring to life the incredible diversity of this ancient arachnid order.
Chapter 1. Introduction
Chapter 2. Theraphosidae
Chapter 3. Nemesiidae
Chapter 4. Antrodiaetidae
Chapter 5. Cyrtaucheniidae
Chapter 6. Ctenizidae
Chapter 7. Dipluridae
Chapter 8. Mecicobothriidae
Chapter 9. Hypochilidae
Chapter 10. Filistatidae
Chapter 11. Segestriidae
Chapter 12. Caponiidae
Chapter 13. Oonopidae
Chapter 14. Dysderidae
Chapter 15. Trogloraptoridae
Chapter 16. Scytodidae
Chapter 17. Sicariidae
Chapter 18. Diguetidae
Chapter 19. Plectreuridae
Chapter 20. Pholcidae
Chapter 21. Leptonetidae
Chapter 22. Telemidae
Chapter 23. Mysmenidae
Chapter 24. Anapidae
Chapter 25. Uloboridae
Chapter 26. Oecobiidae
Chapter 27. Mimetidae
Chapter 28. Nesticidae
Chapter 29. Theridiidae
Chapter 30. Araneidae
Chapter 31. Tetragnathidae
Chapter 32. Pimoidae
Chapter 33. Linyphiidae
Chapter 34. Anyphaenidae
Chapter 35. Miturgidae
Chapter 36. Clubionidae
Chapter 37. Corinnidae
Chapter 38. Liocranidae
Chapter 39. Prodidomidae
Chapter 40. Gnaphosidae
Chapter 41. Salticidae
Chapter 42. Thomisidae
Chapter 43. Philodromidae
Chapter 44. Selenopidae
Chapter 45. Sparassidae
Chapter 46. Homalonychidae
Chapter 47. Zoridae
Chapter 48. Dictynidae
Chapter 49. Cybaeidae
Chapter 50. Hahniidae
Chapter 51. Zodariidae
Chapter 52. Tengellidae
Chapter 53. Pisauridae
Chapter 54. Zoropsidae
Chapter 55. Oxyopidae
Chapter 56. Lycosidae
Chapter 57. Agelenidae
Chapter 58. Amaurobiidae
Chapter 59. Titanoecidae
Chapter 60. Desidae
Chapter 60. Amphinectidae

Plate 1. Theraphosidae
Plate 2. Nemesiidae, Antrodiaetidae
Plate 3. Ctenizidae and Cyrtaucheniidae
Plate 4. Cyrtaucheniidae cont., Mecicobothriidae, Dipluridae
Plate 5. Hypochilidae, Filistatidae, Segestriidae
Plate 6. Caponiidae and Oonopidae
Plate 7. Dysderidae, Scytodidae, Trogloraptoridae, Sicariidae
Plate 8. Plecturidae and Diguetidae
Plate 9. Pholcidae (1 of 2)
Plate 10. Pholcidae (2 of 2)
Plate 11. Leptonetidae, Telemidae, Mysmenidae, Anapidae
Plate 12. Uloboridae, Oecobiidae
Plate 13. Mimetidae, Nesticidae
Plate 14. Theridiidae (1 of 4)
Plate 15. Theridiidae (2 of 4)
Plate 16. Theridiidae (3 of 4)
Plate 17. Theridiidae (4 of 4)
Plate 18. Araneidae (1 of 5)
Plate 19. Araneidae (2 of 5)
Plate 20. Araneidae (3 of 5)
Plate 21. Araneidae (4 of 5)
Plate 23. Tetragnathidae (1 of 2)
Plate 24. Tetragnathidae (2 of 2), Pimoidae
Plate 25. Linyphiidae (1 of 2)
Plate 26. Linyphiidae (2 of 2)
Plate 27. Anyphaenidae, Miturgidae, Clubionidae
Plate 28. Corinnidae
Plate 29. Liocranidae, Zoridae, Prodidomidae
Plate 30. Gnaphosidae (1 of 3)
Plate 31. Gnaphosidae (2 of 3)
Plate 32. Gnaphosidae (3 of 3)
Plate 33. Salticidae (1 of 5)
Plate 34. Salticidae (2 of 5)
Plate 35. Salticidae (3 of 5)
Plate 36. Salticidae (4 of 5)
Plate 37. Salticidae (5 of 5)
Plate 38. Thomisidae (1 of 2)
Plate 39. Thomisidae (2 of 2)
Plate 40. Philodromidae
Plate 41. Selenopidae, Sparassidae, Homalonychidae
Plate 42. Dictynidae
Plate 43. Hahniidae, Cybaeidae
Plate 44. Pisauridae, Tengellidae, Zoropsidae
Plate 45. Oxyopidae
Plate 46. Lycosidae (1 of 2)
Plate 47. Lycosidae (2 of 2)
Plate 48. Agelenidae (1 of 2)
Plate 49. Agelenidae (2 of 2), Amaurobiidae
Plate 50. Desidae, Amphinectidae, Titanoecidae, Zodariidae
R.J. Adams is a special education teacher and wildlife tour leader in Monterey, California. He has a BS in biology from Humboldt State University, California and an MS in biology emphasizing entomology and host-parasite coevolution from the University of Utah.

Tim D. Manolis is an artist, illustrator, and biological consultant. From 1986 to 1990, he was the editor and art director of the magazine Mainstream. His papers on birds and his bird illustrations have appeared in many journals and magazines. He is the author of Dragonflies and Damselflies and illustrator of Butterflies of the San Francisco Bay and Sacramento Valley Regions.
"This guide will be your go-to reference."—Bob Walch The Californian


With over 40,000 described species, spiders have adapted to nearly every terrestrial environment across the globe. With its wide variety of habitats, from montane meadows and desert dunes to redwood forests and massive urban centers, it is not surprising that over half of the world's spider families live within the three contiguous Pacific Coast states. Any place you look, spiders will almost certainly be found, and when time is taken to notice their multitude of lifestyles and forms, it is difficult not to appreciate the incredible diversity of this ancient arachnid order.

The purpose of this guide is to help the interested naturalist identify many of the region's spiders to family, and when possible, to genus and species. Identifying spiders to this level can be extremely difficult, often requiring a detailed examination of the spider's reproductive structures under a microscope. While color and pattern can provide useful clues when identifying many spiders, there can also be great deal of variation, even within a single species. This book covers all of the families and many of the genera found along the Pacific Coast of the contiguous United States. However, it should be kept in mind that unlike birds, mammals, and other vertebrates, the distribution and habitat requirements of most invertebrates are poorly known. In some cases, the only published information on a species is its original description. It is not unheard of to find spiders many miles outside their described range, especially among species that disperse by ballooning. Because this book is meant to be useful in the field, most of the features discussed are those that can be seen with a good quality 10x hand lens, although in some cases smaller structures, such as the spider's claw arrangement or cheliceral dentition are mentioned when they provide the most definitive diagnostic characters. As small, affordable digital cameras have increasingly powerful macrophotographic capabilities, important features such as a spider's eye arrangement and clypeus height can often be seen with relative ease, even on freely-moving individuals.

Understanding spider systematics

Like all living things, spiders are classified using Linnaean taxonomy. In this system, organisms are ideally clustered together based on shared features that reflect their common ancestry. The categories within this system start very broadly and become increasingly specific. To illustrate this point, the taxonomy of the Western Lynx Spider, Oxyopes scalaris is shown.


Kingdom Animalia (all animals)

Phylum Arthropoda (Invertebrates with a chitinous exoskeleton and jointed appendages,

including among others, spiders, insects, centipedes, and crustaceans)

Class Arachnida (Arthropods with two body segments and eight legs, including spiders,

scorpions, and ticks.

Order Araneae (Spiders)

Suborder Opisthothelae (Spiders with non-segmented abdomens and spinnerets

near the posterior abdominal margin. This includes all New World spiders)

Infraorder Araneomorphae ("True" spiders)

Family Oxyopidae(Lynx Spiders)

Genus Oxyopes (One of three North American lynx spider genera)

Species Oxyopes scalaris (Western Lynx Spider)

One of the most important divisions in spider systematics separates all North American spiders into one of two infraorders, Mygalomorphae and Araneomorphae. Mygalomorphae includes the tarantulas and trapdoor spiders. They have several features held over from early in the evolutionary lineage of spiders including four book lungs and parallel chelicera. The second infraorder, Araneomorphae, contains what are occasionally referred to as the "true" spiders, and include all of the most common "household" spiders. Except for members of the family Hypochilidae (p. 56), araneomorphs have only two book lungs and chelicerae that move at an angle towards one another. They are further divided into entelegyne and haplogyne families. Female entelegyne spiders, with a few exceptions, have an intricate, sclerotized reproductive organ called the epigynum while the adult males have architecturally complex palps for transferring sperm. The structure of these organs is extremely important in identifying nearly all spider species. The haplogyne spiders, much like the mygalomorphs, have comparatively simple reproductive organs. They lack the entelegyne's ornate epigynum and the male's palps are little more than a bulb tipped by a long, hollow embolus.



Like all arachnids, spiders' bodies are divided into two main parts, the cephalothorax and abdomen. When measuring a spider or when its size is given in the text, it is the combined length of these two body parts and does not include the legs. The cephalothorax holds the mouthparts, eyes, and legs. A spider's jaws consist of their chelicerae and a pair of hinged fangs. When at rest, the fang lies within a cheliceral furrow which is often bordered by numerous teeth and smaller denticles. The arrangement of a spider's cheliceral dentition is often used to differentiate closely related genera and species. Also part of the spider's mouthparts are the pedipalps, often referred to simply as the palps. Resembling a fifth pair of legs, the palps are used for tactile and chemosensory purposes as well as food manipulation. On adult males, their tips house the spider's reproductive organs. The palps are also coated with chemoreceptive hairs which are used to find and follow female spiders' pheromone trails. On females, these hairs are not as dense, and are mainly used to "taste" their prey before eating it. At the base of the palps are two expanded plates called endites that border the mouth. Along their anterior margin are occasionally found swellings or rows of minute teeth, forming a structure called the serrula. Posterior to the mouth is the labium. Rows of setae on the labium and endites act as filters, removing particulate material from the spider's predigested, liquefied meal.


The area between the top of a spider's chelicerae and its eyes is the clypeus and its shape can be important when separating some groups of spiders. The size and arrangement of a spider's eyes is an incredibly important diagnostic feature. While the majority of spiders have eight eyes, many have only six. A few spiders, typically deep leaf-litter and cave dwelling species, have four or fewer eyes. Spider eyes are generally divided into four pairs based on their shape and location. In front are the anterior median eyes (AME) which are bordered by the anterior lateral eyes (ALE). Behind these are the posterior median (PME) and posterior lateral (PLE) eyes. The carapace, which covers the upper surface of the cephalothorax, often carries an invagination called the fovea or thoracic groove. It provides an internal attachment point for the stomach muscles and its shape can be useful for distinguishing some similar genera and families.On the underside of the cephalothorax is the sternum which is surrounded on either side by the spider's legs. In some genera, there are small, sclerotized points between the sternum and the legs called precoxal triangles. Each leg is composed of eight segments, the basal-most, where the leg attaches to the body, is the coxa. Next is the trochanter which distally attaches to the femur, which is often the thickest leg segment. Past the femur are the patella and tibia. The number and arrangement of spines on the tibia is often a very informative feature when identifying spiders. The last segments are the metatarsus and tarsus, which is tipped by the spider's claws. While extremely small, the number of claws on each spider's leg is an important character, both ecologically and taxonomically. Many of the two-clawed spiders have conspicuous tufts of setae between their claws and are cursorial or arboreal hunters. The three-clawed spiders generally use webs to capture their prey with the tiny central claw helping grip the strands of silk. Spider legs (and leg segments) are often referred to by their location on the spider's body. Going down one side of a spider, the leg closest to the front is known as leg I while at the rear is leg IV. Using this method, if a description refers to "femur II", it is referencing the femur on the second leg from the front.

Connecting the cephalothorax to the abdomen is the pedicel. In some species, there is a dark stripe running down the midline of the abdomen's dorsal surface. This is the heart mark or cardiac mark. In others, there may be shiny plates called scutes partially or entirely covering the abdominal surface. At the posterior end of the abdomen are the spinnerets. While most mygalomorphs have only two pairs of spinnerets, the majority of araneomorphs have three. The anterior lateral spinnerets (ALS) are generally the largest, followed by the posterior lateral spinnerets (PLS). The posterior median spinnerets (PMS) are the smallest and are often hidden by the other pairs. Just anterior to the spinnerets on cribellate spiders is a plate (sometimes divided in two) called the cribellum. Its surface is covered with hundreds of tiny spigots that produce an unusual grayish-blue silk that regularly has a "teased" or carded appearance. On cribellate spiders there is almost always a distinctive row of short, curved setae along metatarsus IV called the calamistrum which combs silk from the cribellum. Those spiders without a cribellum (the ecribellate spiders) often have in its place, a small, fleshy protuberance or setal cluster known the colulus.

Anterior to the spinnerets in the araneomorphs is the tracheal spiracle. Part of the spider's respiratory system, the trachea enters the body cavity where its thin walls allow gas exchange to occur between the air and the spider's hemolymph. Respiratory functions are also carried out by the spider's book lungs. Mygalomorphs and members of the araneomorph family Hypochilidae each have two pairs of book lungs while most of the remaining families have only one. The entrance to each lung is a narrow slit on the underside of the abdomen, often marked by a bare patch of surrounding cuticle. Internally, they are made up of many thin, hollow sheaths, similar to the pages of a book. Between these leaves the spider's hemolymph flows and gas exchange occurs. In araneomorphs, the book lungs are located on either side of the epigastric furrow.

Life history

Female spiders bundle their eggs together into egg sacs. These can vary from a few silken threads to a multilayered packet made of several kinds of silk along with protective layers of dirt and debris. In many cases the egg sac's appearance can be tied to a particular family, genus, or even species. When an egg hatches, the spiderling is in an immobile post-embryonic state and is only able to leave the egg sac after undergoing one or two additional molts. With some exceptions, the spiderlings generally disperse soon after exiting. Many araneomorph spiderlings balloon away from their natal grounds by climbing to the top of a twig and releasing several long strands of silk into the wind. Carried away by the breeze, most are deposited close to their take-off point, however, others can travel hundreds of kilometers and have been collected thousands of meters above the ground. This is the origin of the shiny gossamer threads commonly seen floating through the air and blanketing large areas in the summer and fall. Adults of some small species will also balloon away from nonproductive hunting grounds. Other spiders, including most mygalomorphs, are unable to balloon. Instead, they disperse by crawling away from their natal site.

As spiders grow, they must molt their rigid exoskeleton. The number of molts required to reach adulthood varies from as few as five for small spiders to more than ten for the largest. When molting, most spiders suspend themselves upside-down. The old carapace then opens along its lateral seams and falls back like a dropping trapdoor. Next, the sides of the abdominal integument begin to tear, freeing up the constricted abdomen within. Lastly, the spider pulls its legs and palps free from its old skin. Mygalomorphs follow the same basic routine, but unlike araneomorphs, they put down a silk sheet, and molt while lying on their backs. The molt before adulthood is referred to as penultimate and is marked on male spiders by a noticeable swelling of the palpal tarsi and on female entelegyne spiders by a darkening of the area around the epigastric furrow. While nearly all araneomorphs stop molting after reaching maturity, female mygalomorphs will continue to molt throughout their comparatively long lives.

After reaching adulthood, male spiders weave a small sheet of silk known as a sperm web, on which he deposits a drop of semen. He then dips the tips of his palps into the semen and draws it into the embolus, a syringe-like structure used to transfer sperm to the female. His palps now "charged", the male leaves the safety of his web or burrow, pursuing females by following the pheromones wafting off their webs, or in the case of wandering spiders, their draglines. In some cases, when a male finds a penultimate female, he will guard her from other males in an attempt to be the first to mate. Upon encountering a receptive female, male spiders immediately begin courtship behaviors. This represents one of the most complex areas in spider biology, ranging from simple web-plucking and light touches with the forelegs to exuberant dance- like displays with flashes of color, palpal drumming, and sound production. Courtship rituals both aid in mate selection and help identify the normally smaller males as something other than a prey item. During mating, the male transfers sperm either into the female's gonopore (mygalomorphs and haplogyne species) or into her epigynum (entelegyne species), where it is stored in the spermathecae until she is ready to lay her eggs. The sperm is released and the eggs are fertilized only when they are being deposited into the egg sacs. Rarely does the male stay with the female after mating, and while an adult male may attempt to mate with multiple females, they have reached the last portion of their lives and inevitably die soon after. The relationship between female spiders and their young varies considerably across taxa. Some species abandon their egg sacs soon after construction while others guard it for an extended period. Although many females die before their eggs hatch, some do live to see their young emerge. Female mygalomorphs (and a few araneomorphs) can be particularly long-lived, and may parent multiple generations over their lifetimes. While many araneomorphs appear to have annual life cycles, surviving for one year and overwintering either in the egg sac or as spiderlings, others may take several years to mature or even have different generations that mature at different rates. This can also be affected by the environment. In some cases, the same species can demonstrate different life history patterns depending on whether they are in a temperate coastal climate or in a more seasonally affected montane one.

Webs and silk

While other organisms can make silk, spiders are unique in that silk is produced throughout their lives from abdominal glands. The surprising physical properties of spider silk are well documented. In some cases it can stretch up to three times its resting length, and ounce for ounce, can be stronger than steel. What is less appreciated are the wide variety of silks spiders produce. Seven different kinds have been recorded, each of which is used for different purposes. These include swathing silk for wrapping prey and egg sacs, dry strands for web scaffolding, and droplets of sticky silk for prey capture, although no one spider produces them all. Cribellate silk is made by the members of numerous araneomorph families and is bluish-gray with a "fuzzy" or tangled look to it. Unlike silk that captures prey with sticky droplets, cribellate silk attaches to an insect's cuticle using molecular forces. Members of several orb-weaving families often include a thick band of UV reflective silk through the hubs of their webs. Known as a stabilimentum, it is normally either a vertical bar or "X" shaped, and may serve a number of purposes, including warning birds away from the web, attracting insects, or aiding in thermoregulation.

Spider webs vary dramatically between families, and in some cases genera. Most araneomorph webs fall into one of five broad categories. Tube webs consist of sock-like retreats with a radiating collar of signal threads around their entrances. They are often hidden in cracks or along the seams of buildings and are made by several families including Filistatidae (p. 60) and Segestriidae (p. 63). Funnel webs consist of a tubular retreat with a platform spreading out from its entrance, such as those made by members of the family Agelenidae (p. 292). Depending on the species, sheet webs consist of one to several flat or curved sheets suspended above the substrate. These kinds of webs are made by the families Pimoidae (p. 163) and Linyphiidae (p. 167). With their iconic circular design, orb webs are among the most familiar of spider webs. A number of families build these, including Araneidae (p. 138) and Tetragnathidae (p. 157). Despite initial appearances, tangle webs are well organized structures with different kinds of silks playing different roles in prey capture and protection. They are built by members of the family Theridiidae (p. 118). Some spiders incorporate multiple elements into a single web, including members of the araneid genus Metepeira. They surround their cup-like retreats and orb webs with an expansive tangle. The Marbled Cellar Spider, Holocnemus pluchei (Pholcidae, p. 89), builds a tangle around a filmy sheet web.With practice, the typical webs of each family are often easily recognized and are described in the family accounts section of this book. Because they are regularly damaged, many spiders repair their webs on a daily basis. Orbweb weavers (Araneidae, p. 138) regularly devour much of their old webbing and recycle its chemical components into a new one.

In addition to catching prey, webs act as extensions of the spider's sensory field. Just as a female spider at one side of a large orb web can feel the vibrations of an entangled fly, she can also feel the rhythmic plucking of a male well before her potential mate is visible. Laced with pheromones, spider silk can inform others about the age, sex, health, and even diet of the spider that made it. Male spiders normally find mates by following the pheromonal "scents" on the female's silk. In some spiders, the male ties the female down with silk as part of the pre-mating courtship ritual. Known as a "bridal veil", it does not constrain her, but pheromones on the silk may play a role in keeping her sedate during the mating process. Pheromones also provide information between species, as some spiders will respond defensively when encountering the fresh dragline of a potential predator. Ballooning spiders use silk to help them disperse and even wandering spiders that don't build webs weave retreats in protected nooks for resting, molting, and brooding their young.

Spiders as predators

Nearly all of the world's spiders are believed to be almost entirely carnivorous. Not surprisingly for such a large and diverse group, spiders have evolved numerous hunting strategies with prey selection ranging from generally broad to highly specialized. At first glance most spider webs appear to be indiscriminate filters catching anything small enough to get tangled in their weave. When their ecological parameters are combined with their genetically determined web architecture, many spiders disproportionately capture only a small subset of the total variety of possible prey items. In most cases, a spiders' diets thus consist of only a few kinds of prey at any given time, with other items making up a minor percentage of their overall intake. Among the most extreme examples of prey specialization are members of the genus Mastophora (Araneidae, p. 138) who spin gluey bolas laced with pheromones that attract male moths of specific species. Many spiders specialize in eating ants. To accomplish this, they construct webs around ant mounds, while others go so far as to infiltrate ant colonies. The desert dwelling Septentrinna steckleri (Corinnidae, p. 184) lives within ant nests, its cuticular hydrocarbons mimicking those of the ants among whom it dwells.

Among cursorial and arboreal hunters, many use vibrations to determine a potential prey item's size and location before attacking. Others, including jumping spiders (Salticidae, p. 208) use their vision to hunt. Several families of trapdoor spiders and many crab spiders (Thomisidae, p. 225) are ambush predators. They stay in one spot, sometimes for most of their lives in the case of trapdoor spiders, waiting for potential prey to come near. Spitting spiders (Scytodidae, p. 77) subdue their prey by spraying it with a sticky mix of glue and venom. While most prey items are insects, many other small animals, including other spiders, earthworms, isopods, and rarely, small vertebrates, can be part of the spiders' dietary regime.

When an insect is captured in a spider's web, the spider will normally respond in one of several ways. If the prey is soft bodied and harmless, such as a moth or a fly, the spider will quickly bite it, immobilizing it before it escapes. If the prey is large and potentially dangerous, such as a wasp or grasshopper, the spider may choose to throw silk over it from a distance, only biting it after the prey is thoroughly ensnared. In some cases, when the prey is especially aggressive or difficult to subdue, the spider may avoid the captured creature entirely and simply cut it out of its web. When a spider bites, venom is injected into the prey though tiny holes at the tips of the fangs. Spider venoms can be divided into two broad categories; neurotoxins, which affect the nervous system, and cytotoxins, which destroy the surrounding tissues. Once immobilized, digestive fluids are regurgitated and the prey's internal organs begin to dissolve. Additionally, some spiders use their cheliceral teeth crush their prey's body, allowing the digestive fluids to act more efficiently. As the organs liquefy, pumping action by the stomach sucks in the fluid with hairs on the labium and endites filtering out the larger particles. Along with animal prey, both crab spiders and jumping spiders have been noted drinking nectar. Several spider families are also known to gain nutritional benefits by eating pollen grains caught in their webs.

Spiders as prey

A great many animals eat spiders, including mammals, reptiles, amphibians, insects, birds, and even other spiders. Pirate spiders (Mimetidae, p. 110) specialize in hunting and feeding on spiders (a term known as araneophagy). Others, including the Long-bodied Cellar Spider Pholcus phalangioides (Pholcidae, p. 89) make them a major part of their diet. In areas with winters cold enough to dramatically reduce insect populations, overwintering spiders are one of the main food sources for small birds. Although passive defenses such as camouflage are extremely common, spiders also employ a wide range of behaviors to dissuade or confuse potential predators. Some species, especially those in the families Corinnidae (p. 184) and Salticidae (p. 208) use color and behavior to mimic stinging ants and wingless wasps. When threatened in their webs, some spiders drop to ground while others rapidly vibrate making them more difficult to capture. Others might play dead or even drop a grabbed leg, giving the predator something to feed on while the spider gets away. Velveteen tarantulas (Nemesiidae, p. 33), have a more assertive defense, rearing up aggressively when disturbed. Threatened tarantulas (Theraphosidae, p. 27) will kick off special barbed setae known as urticating hairs from their abdomens. These irritating hairs can get caught in a predator's skin, and if close enough, will severely irritate its eyes and respiratory system. Some small rodents have even suffocated from urticating hairs caught in their throats. Female Green Lynx Spiders Peucetia viridans (Oxyopidae, p. 277) are exceptional in that they can spray a burst of venom from their fangs when threatened.

Spiders are also highly susceptible to parasites, both external and internal. Several common wasps (order Hymenoptera), including spider wasps (family Pompilidae) and thread-waisted wasps (family Sphecidae) paralyze spiders and lay an egg on their living, but immobilized, bodies. The wasp then entombs the spider, providing a fresh source of food for its developing young. Some ichneumonid wasps (family Ichnuemonidae) attach an egg directly to the spider's abdomen. The ectoparasitic larva then feeds on its still active host's bodily fluids. Other ichnuemonids and some genera of mantidfly (order Neuroptera, family Mantispidae) will insert their eggs into a spider's egg sac. The young parasitoid then feeds on the spider's eggs, eventually emerging as an adult. Among the numerous families of flies (order Diptera) that parasitize spiders and their egg sacs are the small-headed flies (family Acroceridae). Female small-headed flies scatter their eggs on the ground, and after hatching, the maggots crawl in search of a host. When a suitable spider is found, they move up its leg and burrow into its abdomen through its book lungs. Relatively unobtrusive for most of its development, during its last instar, the larva devours its host from the inside. It then pupates in the expired host's retreat.

Studying spiders

There are three main ways one can study spiders; alive in the field, in captivity, or preserved as part of a permanent collection. A great deal is still unknown about many North American spiders, including their food preferences, egg sac design, growth rates, courtship behaviors, and other aspects of their natural history. Finding spiders isn't difficult. They are in nearly every habitat, and different genera and families often live in fairly specific ecological niches. Just as members of the genus Tetragnatha (Tetragnathidae, p. 157) most commonly build their large, open orb webs over creeks, seeps, and other wet places, the Common House Spider Parasteatoda tepidariorum (Theridiidae, p. 118) is almost always found around homes and other dwellings. By taking note of their behaviors, diets, periods of activity, and habitats, new information about how spiders live will almost certainly be revealed. Spiders can be studied alive in the field in several ways. With advances in close-focus binoculars and the ability of small digital cameras to take good quality macrophotographs, basic behavioral observations are becoming increasingly easy to make. Another highly effective technique for looking at small features on living spiders requires a clear, sandwich-size, resealable plastic bag and a 4" embroidery hoop. Embroidery hoops consist of two tightly interlocking wooden rings, a solid inner one and an adjustable outer one, and are available at any fabric store. Once the spider is coaxed into the bag, seal it and place the spider near the center of the outer ring. Then insert the inner ring, which should pull the bag tight. This immobilizes the spider without injuring it. With a 10x hand lens or jewelers loupe, you can then examine many important anatomical features that would otherwise be impossible to see on a still living spider.

When studying spiders, taking notes and field sketches will both significantly improve the quality of your observations and add to their scientific value. While note taking is a very personal activity, many wildlife professionals employ the Grinnell method. Named after Joseph Grinnell, the first director of the University of California Berkeley's Museum of Vertebrate Zoology, this method uses several steps to promote detailed, accurate record keeping. The first step is creating a field notebook, where immediate notes, including the date, time of day, habitat, elevation, species lists, and any field observations are made. This information is later transcribed into a more readable field journal where quickly written notes are organized into clearly written daily entries. If one is interested in a particular species then a third section, with pages dedicated to that species, are maintained. The last section is a record (linked to earlier sections) of specimens collected. By keeping such detailed notes, one's learning curve is greatly accelerated and it is very likely that new biological and distributional information will come to light. This is also one of the best ways that amateur naturalists can contribute to scientific knowledge. If well maintained, the notes can provide extremely valuable information on the plants and animals of an area many years after they were first written.

Some spiders are diurnal and others are mainly nocturnal, so an outing at night will reveal an entirely different assemblage than a walk during the day. Nocturnal orb weavers can be seen in the heart of their webs, trapdoor spiders wait at the edge of their burrows, and the reflected eye shine of wolf spiders often looks like glittering stars scattered across the ground. When looking for spiders at night, it is best to have a powerful headlamp to keep your hands free. At night (and during the dry parts of the day) nearly invisible webs can be revealed with the use of a "duster". This can be made by putting a small bit of corn starch in the bulb of a turkey baster. When squeezed, a "puff" of corn starch will settle on any nearby webs, revealing their structure in intricate detail. Another trick is to put corn starch inside an old sock (which in turn should be carried in a sealed plastic bag). When lightly beaten over a web, a mist of corn starch falls on to it, highlighting its otherwise invisible architecture.

Because most species are only identifiable as adults, it is often necessary to rear immature spiders to maturity. Many species are easy to keep in captivity and even make fascinating pets. Spiders are generally solitary creatures and each should be kept in its own container. If one is attempting to breed a pair, the male can be introduced into the female's enclosure, but should then be removed after mating to prevent cannibalism. A wide variety of containers can be used to house captive spiders from small plastic cups to large terrariums. Burrowing spiders require soil that is at least twice as deep as the spider is long and web building spiders need a scaffold that is appropriate for the kind of web they construct. Spiders also need hiding places incorporated into their enclosure, such as small rocks, bark, and shards of pottery. Generally spiders eat insects slightly smaller than themselves between once and twice a week. They should also have a constant supply of water. Larger spiders do well with a small dish of water refilled daily, while for smaller spiders, a cotton or sponge-plugged vial will prevent them from falling in and drowning. As spiders prepare to molt, they often become lethargic, secretive, and stop eating. Molting is a risky period, especially for young spiders in captivity, and injuries are relatively common. Not only is the process itself challenging, but immediately after molting, spiders are soft and fairly defenseless. For this reason, all food items should be removed from the spider's enclosure before molting and none put back in for at least a day, giving the spider's newly exposed exoskeleton a chance to harden.

Efficiently capturing spiders can be done in several ways. In weedy or grassy fields sweep nets are used. For collecting spiders from taller, woody vegetation, a beat sheet is invaluable. This is a square of white cloth pulled taught on a wooden frame. When the branches of a bush are shaken over it, insects and spiders drop onto the sheet. If a beat sheet isn't available, a large-mouthed muslin net can also be very useful. Wandering spiders are most easily collected with a pitfall trap. These are easily constructed from two-liter plastic soda bottles by cutting the top off of a bottle just below where it stops curving and becomes straight sided. By inverting the top back into the bottle, a funnel is created. Anything that falls into it then drops down into the main body of the bottle.The pitfall trap is buried with its upper edges flush with the ground. A wooden board, slightly raised with pebbles or screws at the corners, is then placed over it, both to protect the trap and to encourage exploration by small invertebrates. If your goal is to capture live spiders, the pitfall must be checked daily. Placing several balls of crumpled paper at the bottom will provide the spiders with places to hide. Otherwise, you will generally find one large spider and the remains of several others at the bottom of your trap. If you are collecting spiders for a permanent or comparative collection, a few inches of preservative fluid should be poured into the bottom of the trap. The best choices are either 70% ethyl alcohol (available at most pharmacies) or propylene glycol (a common antifreeze), mixed with some water to reduce its surface tension. Never use ethylene glycol, another common antifreeze that is both attractive and toxic to mammals. It is important to mark the trap so it can be found again and always remove pitfalls once you're done collecting at that location. Spiders are also abundant in leaf litter. The easiest way to find these is by spreading out small handfuls of duff on a white cloth or plastic sheet (cut up shower liners work very well), and looking for movement as the spiders scurry away. The litter can also be placed in a mesh bag and sifted over the sheet.

Many spiders are collected using an aspirator or pooter. In its simplest form, an aspirator consists of several feet of elastic tubing with a few inches of stiff plastic pipe sticking out from one end. The stiff piece extends back an inch or two into the tubing and is capped on the inside with a small piece of screen or mesh. To collect a spider, you suck in at the tubing end and vacuum the spider into the pipe. To avoid sucking mold or spores into your lungs, one should avoid aspirating directly from the ground or from rotting logs. A slightly more complex version consists of two pieces of tubing extending from a vial plugged with a rubber stopper. With this arrangement, the spider is trapped in the vial rather than at the end of the tubing.

Maintaining a spider collection can be very important, both as a means of verifying a specimen's identity, and by creating voucher specimen representing a specific date and locality. Unlike insects which are often pinned, spiders are preserved in alcohol. While the alcohol often bleaches out the spider's coloration, it preserves their diagnostic anatomic structures. The best fluid for preserving spiders is 70-80% ethanol or ethyl alcohol, although in a pinch, isopropyl, or rubbing alcohol can be used. Avoid alcohols with perfumes or dyes. While never pleasant, killing spiders is necessary to make a preserved collection. Many people place the living spider directly into alcohol in the field. Another technique that works well is keeping a jar of alcohol in the freezer. A living spider dropped in the cold alcohol is quickly killed. A few seconds later it can be removed and placed in vial of room-temperature alcohol for permanent storage. The next step is to write data labels to accompany the specimens. This is extremely important, as a specimen without associated data is scientifically worthless. At a minimum, the information should include the date, written with the month either partially spelled out or in Roman numerals, where the spider was found, including the specific locality, county, state, and if known, its GPS coordinates, and the collector's name. Additional desired information would include habitat and brief behavioral notes, elevation, method of collection, and time of day collected (if known). A separate identification label should include the scientific name of the spider, the name of the scientist who first described it, the year it was described, who identified it (the determiner), and the year the determination was made. It should also include a note regarding the numbers and sexes of spiders of the same species in the vial. It is important not to mix up collections to ensure that all spiders stored in the same vial were collected at the same place and time. The labels should be written on 100% cotton paper (easily found in art supply stores) and written in archival or India ink. Pencil is also relatively stable in alcohol and may be used. Never use computer printed labels or ball point pens as these quickly fade, dissolve, or leach into the alcohol. The labels are then slipped into the vial with the spiders as a permanent record. The best vials for preserving spiders are glass with screw caps lined with a polyseal insert to prevent evaporation. Tightly sealed small jars can also be used for larger specimens as long as the alcohol levels are checked regularly and refilled when necessary. Nearly all entomological research supplies can be purchased through companies such as BioQuip (URL listed under the additional resources section). Exposure to light will quickly fade specimens, so when they are not in use, they should be kept in a dark cabinet or closed cupboard. Because alcohol is flammable, keep specimens away from heat sources and a fully-charged fire extinguisher should always be kept nearby.

Spiders around the home

The most familiar spiders are those found around homes. These are generally synanthropic species whose evolutionary adaptations have acclimatized them especially well for living in houses and other buildings. Nearly all of these spiders are from other parts of the world, having traveled to North America on boats, trains, and in agricultural supplies. Although any spider bite can be serious if it becomes infected or if the person receiving it is exceptionally sensitive to the venom, almost none of the region's common household spiders is considered genuinely dangerous with the exception of the native Western Black Widow, Latrodectus hesperus (Theridiidae, p. 118).


1. Woodlouse Hunter, Dysdera crocata (Dysderidae, p. 73, plate 7). Most likely native to the Mediterranean region. Common in California and Oregon, less so in Washington.

2. Long-bodied Cellar Spider, Pholcus phalangioides (Pholcidae, p. 89, plate 9). Native to central Europe. Common in California, Oregon, and Washington.

3. Marbled Cellar Spider, Holocnemus pluchei (Pholcidae, p. 89, plate 9). Native to the Mediterranean region. Widespread in California and Oregon.

4. Wall Spider, Oecobius navus (Oecobiidae, p. 107, plate 12). Cosmopolitan. Place of origin unknown. Found in California, Oregon, and Washington.

5. Western Black Widow, Latrodectus hesperus (Theridiidae p. 118, plate 14). Native to western North America. Common in California, Oregon, and Washington.

6. Brown Widow, Latrodectus geometricus (Theridiidae p. 118. plate 14). Cosmopolitan. Place of origin unknown. Extremely common in southern California.

7. False Black Widow, Steatoda grossa (Theridiidae p. 118, plate 14). Native to Europe. Found in California, Oregon, and Washington.

8. Common House Spider, Parasteatoda tepidariorum (Theridiidae p. 118, plate 14). Cosmopolitan.Place of origin unknown. Found in California, Oregon, and Washington.

9. Long-legged Sac Spiders, Cheiracanthium spp. (Miturgidae, p. 179, plate 27). Native to Africa and Mediterranean regions. Widespread in California, uncommon to very rare farther north.

10. Mouse Spider, Scotophaeus blackwallii (Gnaphosidae, p. 197, plate 31). Native to Europe. Common in coastal California, Oregon, and Washington.

11. Johnson Jumper, Phidippus johnsoni (Salticidae, p. 208, plate 33). Common throughout the Pacific Coast states.

12. Wall jumpers, Menemerus spp. (Salticidae, p. 208, plate 36). Native to the Old World tropics and Mediterranean region. Widespread in California.

13. Zebra Jumper, Salticus scenicus. (Salticidae p. 208, plate 36). Holarctic, possibly introduced to North America. Common in California, Oregon, and Washington.

14. False Wolf Spider, Zoropsis spinimana. (Zoropsidae, p 275, plate 44). Native to the Mediterranean region. Common and spreading throughout California's San Francisco Bay Area.

15. Funnelweb weavers, Tegenaria spp. (Agelenidae, p. 292, plate 48). Native to Eurasia. Common throughout California, Oregon, and Washington.

16. Gray House Spider, Badumna longinqua. (Desidae, p. 305, plate 50). Native to Australia. Widespread along the coasts of California and Oregon.


17. Metaltella simoni (no common name). (Amphinectidae, p. 307, plate 50). Native to South America. Very common in southern California.


Additional resources

There is a great deal of information about spiders available both in print and on the worldwide web. Unfortunately, much of this information is incorrect and it can be difficult to determine which resources to trust. While not exhaustive, the following books and internet sites are well-regarded and can provide accurate information on spiders and other arachnids.


Books (the full citation of each book can be found in the reference section)

Spiders of North America: An Identification Manual (2005) by Darrel Ubick, Pierre Paquin, Paula E. Cushing, and Vincent D. Roth (eds). This incredibly detailed manual allows one to accurately identify North America's spider fauna to family and genus. It is not a field guide but a scientific manual for preserved specimens and nearly always requires examining spiders under a dissecting microscope.


Common Spiders of North America (2013) by Richard Bradley. This richly illustrated book describes nearly 500 of the most widespread and distinctive spiders in North America.


Spiders and their Kin. A Golden Guide (2002) by Herb and Lorna Levi. This is a pocket-sized field guide to many of North America's common spiders with additional information on other arachnid orders from around the world.


Arachnids (2009) by Jan Beccaloni. A beautiful full-color book covering the diversity, biology, distribution, and ecology the class Arachnida. While broad in its coverage, it does an exemplary job reviewing what is known about each of the arachnid orders and contains many stunning photos.


Biology of Spiders (1996) by Rainer F. Foelix. This book provides an in-depth review of many aspects of spider natural history, including their ecology, development, and physiology.


Internet resources

World Spider Catalog

This continuously updated website provides the most up-to-date taxonomic coverage of the world's spiders along with their accompanying bibliographic citations.


American Arachnological Society.

The homepage for the American Arachnological Society and link to the Journal of Arachnology. Most of the journal's articles are available for free download.


American Museum of Natural History Scientific Publications

This site allows free access and downloads of the American Museum of Natural History Publications. These include American Museum Novitates and the Bulletin of the American Museum of Natural History, both of which have published numerous articles of arachnological interest.


Biodiversity Heritage Library

This free database allows one to access thousands of publications, including many important out-of-print journal articles on spider biology and taxonomy.


Spider research, University of California, Riverside

Dispelling myths and rumors, the information on this site reviews many of the stories and urban legends that have sprung up around spiders over the years, providing instead factual information regarding the perceived "threats" from many spider species.



Unlike the sites above, BugGuide is a photo collection publicly edited by both professional entomologists and amateur enthusiasts. Hosted by Iowa State University's Department of Entomology, this photo gallery and archive is organized by an active community of people interested entomology and arachnology. While not a "professionally" curated photo collection, many of the contributors are quite knowledgeable and a great deal of good information is freely shared.


Arachnology resources


While numerous companies sell equipment and materials for biological research, BioQuip is the largest company specializing in entomology and arachnology supplies and books.

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