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

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

Text by R. J. Adams
Illustrations by Tim D. Manolis
Copyright Date: 2014
Edition: 1
Pages: 452
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  • Book Info
    Field Guide to the Spiders of California and the Pacific Coast States
    Book Description:

    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.

    eISBN: 978-0-520-95704-6
    Subjects: Zoology

Table of Contents

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  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
    (pp. ix-x)
    (pp. 1-26)

    WITH OVER 40,000 DESCRIBED SPECIES, spiders have adapted to nearly every terrestrial environment across the globe. Considering the wide variety of habitats in California, Oregon, and Washington, 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 this region. Any place you look, you will almost certainly find spiders, and when you take time to notice their many lifestyles and forms, it will be difficult not to appreciate the incredible diversity of this ancient arachnid order.

    The purpose of this guide is to...


    • THERAPHOSIDAE Tarantulas or Baboon Spiders
      (pp. 28-32)

      IDENTIFICATION: While the family Theraphosidae contains the largest spiders in North America, it also includes several small desert-dwelling species. All tarantulas have urticating hairs on their abdomens and thick claw tufts on each tarsus. Adult males have two-pronged tibial mating spurs on their first legs. The larger species have thick coats of long hairs over an underlying pubescence, giving them a distinctly furry look, while on smaller species, the long hairs are finer and more diffuse, giving these spiders a more velvety appearance.

      SIMILAR FAMILIES: Members of the family Theraphosidae are most likely to be mistaken for velveteen tarantulas (Nemesiidae,...

    • NEMESIIDAE Velveteen Tarantulas, Aggressive False Tarantulas
      (pp. 33-35)

      IDENTIFICATION: Several common names have been used to describe North America’s Nemesiidae, butvelveteen tarantulais arguably the most descriptive. They are large spiders, 16 to 30 mm (.63 to 1.2 in.) in length, with a distinctive smooth “velvety” pubescence covering their bodies. They have exceptionally long posterior lateral spinnerets and three tarsal claws, lack claw tufts, and range in color from silvery gray to brown with purplish iridescence on their palps and fore legs. They are also more aggressive than other Pacific coast mygalomorphs. When disturbed, they readily raise their front legs and expose their large fangs. If further...

    • ANTRODIAETIDAE Folding-door Spiders, Trapdoor Spiders, Turret Spiders
      (pp. 35-39)

      IDENTIFICATION: Antrodiaetids are small to medium-size mygalomorphs, 6 to 25 mm (.24 to .98 in.) in length, with one to four sclerotized patches on the dorsal abdominal surface. Members of the family Antrodiaetidae have posterior lateral spinnerets that are quite long and capped by a fingerlike terminal segment. The anterior portions of their carapaces are distinctly elevated, and the thoracic groove shape varies. Antrodiaetidae range in color from grayish yellow to dark mahogany brown. Because of this family’s secretive nature, the individuals most commonly encountered are adult males wandering in search of females.

      SIMILAR FAMILIES: Antrodiaetids are superficially similar to...

    • EUCTENIZIDAE Wafer-lid Trapdoor Spiders
      (pp. 39-42)

      IDENTIFICATION: Euctenizidae represents a diverse group of small to medium-size mygalomorphs, many of whom have distinctive abdominal patterns or build unusual burrow entrances. The major morphological features used to describe this family include a lack of abdominal sclerites, the presence of fairly dense scopulae on the tarsi and metatarsi of their anterior legs, and teeth only on their cheliceral promargins. All of the North American genera were previously housed in the family Cyrtaucheniidae, but in their major revisionary work, Bond et al. (2012b) split them from the South American and Old World genera and placed them in the newly established...

    • CTENIZIDAE Cork-lid Trapdoor Spiders
      (pp. 43-46)

      IDENTIFICATION: The most obvious feature regarding these robust spiders isn’t morphological but architectural. Their thick-lidded trapdoors are unique among the Pacific coast’s spider fauna and in many cases are the only visible evidence of these spiders’ presence. The West Coast’s Ctenizidae are moderately large spiders, 15 to 28 mm (.6 to 1.1 in.) in length, although there is a great deal of variation between populations (W. Icenogle, pers. comm., 2008). They are mostly dark mahogany brown to black while the abdomens of adult males have an unmarked dusky reddish or purplish hue. The corklid trapdoor spiders lack abdominal sclerites, their...

      (pp. 46-47)

      IDENTIFICATION: These tiny mygalomorphs, 3 to 5.5 mm (.12 to .22 in.) in length, lack abdominal sclerites and have only two pairs of spinnerets, and although the posterior lateral spinnerets are quite long, they’re not pseudosegmented.

      SIMILAR FAMILIES: The only spiders likely to be mistaken for a diplurid are members of the family Mecicobothriidae (p. 47). Superficially similar, mecicobothriids have abdominal sclerites and pseudosegmented posterior lateral spinnerets. Additionally, other thanHexura rothi,all regional mecicobothriids have three pairs of spinnerets.

      PACIFIC COAST FAUNA: One genus with one regional species. The Pacific coast’s only diplurid isMicrohexura idahoana(pl. 4), an...

      (pp. 47-49)

      IDENTIFICATION: These small mygalomorphs are identified by the presence of both elongate, pseudosegmented posterior lateral spinnerets and abdominal sclerites. Males also have an unusual palpal structure in which the tarsus extends cymbium-like over the bulb. Unlike other mygalomorphs, the Mecicobothriidae thoracic groove is longitudinal and shallow.

      SIMILAR FAMILIES: Mecicobothriids share several features in common with members of the family Dipluridae (p. 46), including their diminutive size, elongate spinnerets, and web design. However, diplurids lack abdominal sclerites and pseudosegmented spinnerets. The only other western mygalomorph family with abdominal sclerites is Antrodiaetidae (p. 35), but those spiders build either trapdoors or turrets...

    • HYPOCHILIDAE Lampshade Weavers
      (pp. 49-52)

      IDENTIFICATION: The lampshade weavers are a remarkable group of long-legged, cribellate spiders, easily recognized both by their unusual physical appearance and by the distinctive architecture of their webs. This ancient lineage retains several features linking them to the earliest araneomorphs. They have two pairs of book lungs like mygalomorphs, and their chelicerae are intermediate in position between the angled alignment of the araneomorphs and the parallel condition of the mygalomorphs. The Pacific coast’s lampshade weavers are eighteyed, medium-size spiders ranging from 7.4 to 10.5 mm (.3 to .4 in.) in length, although their exceptionally long, thin legs can make them...

    • FILISTATIDAE Crevice Weavers
      (pp. 52-54)

      IDENTIFICATION: This is a morphologically diverse group of haplogyne, cribellate spiders. They range in length from 1.5 to 18 mm (.06 to .7 in.) and vary considerably in their color and shape. A spider in this family has eight eyes tightly clustered on a central mound, chelicerae that are fused at their bases, and an abdomen often covered with dense, velvety setae. Additionally, the filistatids exhibit tibia-patella autospasy, an uncommon defensive condition in which the leg separates from the rest of the body at the tibia-patella joint when grabbed. They are secretive spiders, and often the only sign of their...

    • SEGESTRIIDAE Tube Web Weavers
      (pp. 54-56)

      IDENTIFICATION: The entrances to their webs are all most people ever see of segestriids. These six-eyed haplogyne spiders build white, wide-mouthed tube webs in protected nooks, including cracks in walls and under peeling bark. Tube web spiders have a distinctive leg arrangement in which legs I through III are directed forward while leg IV points backward. The posterior eye row is either straight or slightly recurved, and the abdomen is fairly long and cylindrical.

      SIMILAR FAMILIES: While several families, including Plectreuridae (p. 70) and Filistatidae (p. 52), make tube webs, none of them have the unusual segestriid leg arrangement and...

      (pp. 56-58)

      IDENTIFICATION: With the exception ofCalponia harrisonfordi,an eight-eyed species from California’s central Coast Ranges, caponiids are unique among North American spiders because they have only two eyes. They are small (2.7 to 5.4 mm, or .11 to .21 in., in length) and haplogyne and lack book lungs. Additionally, they have an especially hairy abdomen, and their posterior median spinnerets are in a transverse row with their anterior lateral spinnerets.

      SIMILAR FAMILIES: With only two eyes, spiders in the generaOrthonopsandTarsonopsare immediately recognizable. With its eight tightly clustered eyes,C. harrisonfordi,however, present an identification challenge. There...

    • OONOPIDAE Goblin Spiders
      (pp. 59-61)

      IDENTIFICATION: Goblin spiders are small (1 to 3 mm, or .04 to .12 in.), six-eyed, haplogyne spiders. They range in color from chalky white to dishwater brown, although the introducedOpopaea concolor(pl. 6) is deep reddish orange. Many species have scuta either partially or fully covering their abdomens. Their eyes are large and conspicuous, either with the posterior medians aligned with the anterior laterals (as inOrchestina) or in a tight cluster, with the posterior medians close to the posterior laterals (as in all other North American genera). Oonopids also have a rather unusual gait, moving in short, jerky...

    • DYSDERIDAE Wood Louse Hunters
      (pp. 61-63)

      IDENTIFICATION: Dysderidae is a haplogyne family represented in North America by a single introduced species, the Wood Louse Hunter,Dysdera crocata(pl. 7). It is a distinctive, medium-size (9 to 15 mm, or .35 to .59 in.) spider with a reddish-orange carapace and legs and an unmarked grayish-yellow abdomen. Its six eyes form a procurved arch, and its jaws are forward pointing, exceptionally large, and readily displayed when the spider is disturbed.

      SIMILAR FAMILIES: Members of the family Caponiidae (p. 59) and several genera in the family Corinnidae (p. 146) share the Wood Louse Hunter’s general carapace and abdominal color...

      (pp. 63-64)

      IDENTIFICATION: Trogloraptorids are long-legged, six-eyed, haplogyne spiders endemic to a small region of caves and old-growth redwood forests in southwestern Oregon and northwestern California. Their most distinctive feature is their subsegmented, raptorial tarsi. Trogloraptoridae are able to fold their large claws against their heavily spined tarsi, creating a grasping structure that is presumably used for holding prey. Additionally, on trogloraptorids, the anterior and posterior lateral eyes are connected, while their posterior medians are separated. There is a membranous band connecting the anterior lateral spinnerets, and there is an unusual double row of teeth on the serrula.

      SIMILAR FAMILIES: With their...

    • SCYTODIDAE Spitting Spiders
      (pp. 64-65)

      IDENTIFICATION: With their smooth, dome-like carapaces and unusual eye arrangement, spitting spiders are unmistakable members of North America’s spider fauna. They are haplogyne, are between 3.5 and 10 mm (.14 and .39 in.) in length, and have six eyes aligned in three dyads forming a recurved arc. Spitting spiders range in color from pale yellow with grayish speckling to nearly black.

      SIMILAR FAMILIES: The recluse spiders (Sicariidae, p. 65) share a number of features with the spitting spiders, including their eye arrangement, overall size, often pale coloration, and a penchant for living under rocks, in homes, and in other structures....

    • SICARIIDAE Violin Spiders, Recluse Spiders
      (pp. 65-68)

      IDENTIFICATION: While many people call any cursorial tan or brown spider a recluse, there are a few key features that you must see to confidently distinguish recluses from other, superficially similar spiders; the most important of these is their eye arrangement. Violin spiders have only six eyes arranged as three pairs in a recurved row. They are fairly small (5 to 13 mm, or .20 to .51 in., in length). They have long, thin legs without spines, only two tarsal claws, and an exceptionally large, fleshy colulus. They range from pale yellow to brownish gray or reddish brown in color,...

    • DIGUETIDAE Desertshrub Spiders
      (pp. 68-70)

      IDENTIFICATION: In California’s deserts and chaparral-covered foothills, a desertshrub spider’s web is structurally unique. It consists of a low-slung sheet surrounded by a cobweb-like tangle with a conical retreat suspended in the center. Desertshrub spiders are haplogynes with fairly flat, oval carapaces and six eyes arranged in three dyads. The abdomen can be either white or patterned, and all of the regional species have boldly banded legs. Additionally, diguetids have three tarsal claws and chelicerae fused at their bases. While each of these anatomical features can be found in other spider families, in combination they are diagnostic of the desertshrub...

      (pp. 70-73)

      IDENTIFICATION: Members of the family Plectreuridae are small to medium-size (5 to 12 mm, or .20 to .47 in., in length), eight-eyed, haplogyne spiders. Their carapaces and legs range from reddish orange to black, and their abdomens vary from yellowish brown to black, often with a pale heart mark on their dorsal surface. As many of the diagnostic features of this fam ily are quite small, a detailed examination may be required to confirm familial identity of a plectreurid. Fortunately, there are only two genera in the region, and once you become familiar with the resident species, recognition of them...

    • PHOLCIDAE Cellar Spiders
      (pp. 73-77)

      IDENTIFICATION: Pholcids are small to medium-size spiders with exceptionally long, thin legs, pseudosegmented tarsi, and three tarsal claws. Except for the very small, six-eyedSpermophora senoculata,all Pacific coast cellar spiders have eight eyes arranged as two tightly clustered triads with the small, but well-developed, anterior median eyes between them. The abdomens of these spiders range from oblong to globose and vary from pale gray to heavily mottled. On many species, the males have spurs or other sexual modifications to either or both their clypei and chelicerae.

      The common name “daddy longlegs” can be confusing. It has been applied not...

      (pp. 77-79)

      IDENTIFICATION: Leptonetids are diminutive (1 to 3 mm, or .04 to .12 in.) haplogyne spiders with a distinctive eye arrangement. Although there are eyeless cave-dwelling species in the south-eastern United States, all of the Pacific coast leptonetids have six eyes, either clustered together in a tight group or with the posterior median eyes resting noticeably behind the other four. In living spiders, the legs are uniquely iridescent, contrasting with their pale-gray to dark-brown bodies. This is one of the few families that exhibits patella-tibia autospasy, a defensive condition in which the leg breaks off at the patella-tibia joint when grabbed...

      (pp. 79-81)

      IDENTIFICATION: Telemids are minute (1 to 1.7 mm, or .04 to .07 in.) haplogyne spiders with a diagnostic zigzag or W-shaped sclerotized abdominal ridge just above the pedicels. Telemid cephalothoraxes range from pale gray to bright orange, and their abdomens are blue green or gray and often clothed in fairly long, diffuse setae. Adult females have a distinctive brush of short, stout setae on the dorsal surfaces of their palpal tarsi. While each of the currently described North American species has six eyes, numerous eyeless cave-dwelling species still await description, making Telemidae among the most diverse of the Pacific coast’s...

      (pp. 81-82)

      IDENTIFICATION: Mysmenids are minute, eight-eyed, entelegyne spiders with three claws on each tarsus. They are found in leaf litter, wood rat middens, and other dark, humid places. Members of the family Mysmenidae can be distinguished from other tiny, cryptic spiders by the presence of a distinctive sclerotized spot on the ventral surface of each femur I. Additionally, adult males have spine-like clasping spurs on metatarsi I and cymbia that twist near their tips.

      SIMILAR FAMILIES: On the Pacific coast,Gertschanapis shantzi(Anapidae, p. 82) is the spider most likely to be confused for a mysmenid. The male G.shantzilacks...

      (pp. 82-83)

      IDENTIFICATION: North America’s only “true” anapid is the tiny, eight-eyedGertschanapis shantzi.The female is unique among Pacific coast spiders in that her palpi have been reduced to minute nubs on the anterior face of the endites. The male’s abdomen is reddish brown, covered by a conspicuous scute, and sculpted with numerous grooves and small sclerotized pits along the sides. Both sexes also have enlarged spur-like tubercles on the ventral surfaces of their first and second femora. The unique web is a small, fine-meshed, horizontal orb in which extensions of the radial threads are strung above the mesh and connect...

    • ULOBORIDAE Hackled Band Orb Weavers
      (pp. 83-85)

      IDENTIFICATION: Uloboridae are small, cribellate, eight-eyed, entelegyne spiders whose Pacific coast representatives are unique, both in their morphologies and in their web designs. Hackled band orb weavers have exceptionally long calamistra that stretch across more than half the length of their dorsally concave fourth metatarsi. They also have multiple rows of trichobothria on femora II through IV and nondivided cribella. There are two kinds of webs made by the Pacific coast’s Uloboridae: a horizontal or sloping orb web with a stabilimentum along the midline, and a vertically aligned triangle.

      SIMILAR FAMILIES: There are several small spiders in the ecribellate families...

    • OECOBIIDAE Wall Spiders
      (pp. 85-88)

      IDENTIFICATION: Members of the family Oecobiidae are small (1 to 4 mm, or .04 to .16 in., in length) cribellate spiders with distinctive enlarged anal tubercles (fig. 9). Their eight eyes are arranged in a compact cluster, and their flat, rounded carapaces range in color from pale yellow to dusky brown. They can be exceptionally common around homes and are often found on walls and ceilings.

      SIMILAR FAMILIES: With their enlarged anal tubercles, distinctive shape, compact eye arrangement, and often synanthropic habits, wall spiders are unlikely to be mistaken for any North American spider family.

      PACIFIC COAST FAUNA: One genus,...

    • MIMETIDAE Pirate Spiders
      (pp. 88-90)

      IDENTIFICATION: Mimetids are small (2.5 to 7 mm, or .1 to .28 in.), eight-eyed entelegynes that specialize in preying on other spiders. The tibiae and metatarsi on their fore legs are armed with a diagnostic row of long spines separated by a series of short, stiff setae. Pirate spiders also often rest in a characteristic pose, with legs I and II extended forward, III held close to the body, and IV projecting backward.

      SIMILAR FAMILIES: Pirate spiders are most likely to be mistaken for either orb web weavers (Araneidae, p. 110) or cobweb weavers (Theridiidae, p. 93), both of which...

    • NESTICIDAE Cave Cobweb Spiders
      (pp. 90-93)

      IDENTIFICATION: Nesticids are eight-eyed (or eyeless), three-clawed entelegynes. The anterior margins of their labia are slightly thickened, a condition referred to as rebordered. There is also a ventral comb of serrated setae on tarsus IV, and an adult male has a large, rigid extension off the base of his palpal cymbium (a paracymbium). Cave cobweb spiders are small (2.5 to 4 mm, .1 to .16 in., in length) and make distinctive “split-foot” tangle webs, so called because they split into two branches at the base, in damp, protected areas, including inside caves, within the interstices of thick leaf litter, and...

    • THERIDIIDAE Cobweb Weavers, Comb-footed Spiders
      (pp. 93-110)

      IDENTIFICATION: Theridiidae houses some of the most familiar spiders on the Pacific coast, including the Western Black Widow(Latrodectus hesperus)and the cosmopolitan Common House Spider(Parasteatoda tepidariorum).Like other members of the superfamily Araneoidea, the cobweb weavers are eight-eyed (with one very rare exception), three clawed entelegynes. Most species have an unusual row of curved, serrated setae on the ventral surface of the fourth tarsi, although this feature may be hard to see or even absent on some males. Theridiids have very few or no leg spines, and the anterior margins of their labia lack rebordered edges. They are...

    • ARANEIDAE Orb Web Weavers
      (pp. 110-125)

      IDENTIFICATION: Araneids are among the most familiar and morphologically diverse of North America’s spider families. With their characteristic web design, orb web weavers are what come to mind when most people think of spiders. They range from 1.5 to 30 mm (.06 to 1.18 in.) in length, and their abdomens can be smooth, lobed, or spiny. While many species are cryptically colored, others are brightly decorated. With one rare exception, the region’s araneids build vertically inclined orb webs, some of which include stabilimenta across their hubs.

      Like other members of the superfamily Araneoidea, including the long-jawed orb weavers (Tetragnathidae, p....

    • TETRAGNATHIDAE Long-jawed Orb Weavers
      (pp. 126-131)

      IDENTIFICATION: Tetragnathidae is a morphologically diverse family of orb weavers regularly found near streams, marshes, and other waterways. Collectively, they are occasionally referred to as long-jawed orb weavers (a common name also applied specifically to members of the genusTetragnatha) because the chelicerae on many species are exceptionally long and adorned with numerous stout teeth. While individual genera are fairly recognizable, the features uniting the family as a whole are subtle and often difficult to discern. Tetragnathidae is part of a larger clade of spiders called Araneoidea that houses some of our most familiar spider families, including the orb web...

      (pp. 131-133)

      IDENTIFICATION: Pimoidae is a small family of eight-eyed entelegyne spiders that is part of a larger superfamily called Araneoidea. This superfamily contains some of our most common spider families, including the cobweb weavers (Theridiidae, p. 93), the orb web weavers (Araneidae, p. 110), and the sheet web weavers (Linyphiidae, p. 133).

      With one very rare exception, pimoids range from 5 to 12 mm (.2 to .47 in.) in length. Most have exceptionally long, moderately spined, reddish-brown legs that are coated with setae and demonstrate patella-tibial autospasy, an adaptation that allows the leg to break away at the patella-tibia joint when...

    • LINYPHIIDAE Sheet Web Weavers, Dwarf Spiders, Money Spiders
      (pp. 133-140)

      IDENTIFICATION: Linyphiids are among the most common spiders in North America, with more described regional species than any other family. However, most are minute inhabitants of the leaf litter, rarely seen by the casual observer. A sheet web weaver’s web consists of one or more horizontal, domed, or concave sheets supported above and below by auxiliary threads. Linyphiids are often found hanging beneath their sheet webs, a position that allows them to attack their prey from below. They range from less than 1 to 8.5 mm (. 04 to .33 in.) in length, although most are under 4 mm (....

    • ANYPHAENIDAE Ghost Spiders
      (pp. 140-143)

      IDENTIFICATION: Ghost spiders are small (3.3 to 6.5 mm, or .13 to .26 in., in length), eight-eyed entelegynes with unique lamel-liform claw tufts. Unlike the thick, brush-like tufts of other two-clawed spiders, the setae on ghost spiders broaden distally, giving them an unusual spatulate appearance. Another distinguishing feature of the anyphaenids is the placement of the tracheal spiracle. On other spiders, it is near the spinnerets, but on ghost spiders, it is either near the midpoint of the abdomen or close to the epigastric furrow. Ghost spiders vary from white to brown, often with darker bands or other markings on...

    • MITURGIDAE Prowling Spiders
      (pp. 143-145)

      IDENTIFICATION: Miturgids are two-clawed entelegynes whose eight eyes are aligned in two broad rows. As in related families, the prowling spiders’ anterior lateral spinnerets are conical and almost contiguous across their bases. The detail that best distinguishes a prowling spider is the shape of its posterior lateral spinnerets, the tips of which are capped by elongate or conical segments. Miturgids also lack a clearly defined thoracic groove. Our regional prowling spiders can be concolorous or patterned, arboreal or terrestrial, and as in other families with diverse genera and a complicated taxonomic history, it is often easier to recognize the genera...

    • CLUBIONIDAE Sac Spiders
      (pp. 145-146)

      IDENTIFICATION: Clubionids are two-clawed entelegynes whose distinguishing features as a family are subtle but whose members are not difficult to recognize once you become familiar with their unassuming appearance. Their anterior lateral spinnerets are conical and nearly connected at their bases, and their posterior lateral spinnerets have short, rounded tips. Their eight eyes are aligned in two fairly straight rows, and they possess a small but clearly visible longitudinal thoracic groove on the dorsal surface of the carapace. There are tiny precoxal triangles around the outer rim of the sternum, and there are three or fewer pairs of spines on...

    • CORINNIDAE Ant-mimic Sac Spiders
      (pp. 146-152)

      IDENTIFICATION: Corinnidae is a diverse family of two-clawed entelegynes that were historically housed in a more broadly defined version of the family Clubionidae (p. 145). Excepting the genusDrassinella,they have conical, anterior lateral spinnerets that are either contiguous or very nearly touching at their bases. Because the four Corinnidae subfamilies are exceptionally diverse, it is easier to describe them separately. Spiders in the subfamily Trachelinae lack leg spines but have numerous tiny cusps on the ventral surfaces of their anterior tibiae and metatarsi, a feature unique both within the family and among the former Clubionidae as a whole. The...

    • PLATES
      (pp. None)
      (pp. 152-155)

      IDENTIFICATION: Liocranids are eight-eyed entelegynes with two tarsal claws but no claw tufts. Historically, Liocranidae’s diverse genera were included in a more broadly defined version of the family Clubionidae (p. 145). Like other former (and current) clubionids, liocranids have conical anterior lateral spinnerets that are either contiguous or only moderately separated at their bases, nearly parallel endites, and a generally cursorial lifestyle. Excepting the genusHesperocranum,members of the family Liocranidae lack precoxal triangles and have pseudosegmented tarsi, at least on their posterior legs. As a family, Liocranidae’s diversity makes it difficult to define, although the genera within it are...

      (pp. 155-156)

      IDENTIFICATION: Members of the family Prodidomidae are regionally very rare, small, two-clawed, entelegyne spiders with enlarged, flattened anterior lateral spinnerets. Their posterior eye rows are strongly procurved, giving them a horseshoe or circular appearance. Additionally, their posterior median eyes are triangular or oval rather than circular, and while their anterior median eyes are dark, the others are silvery gray.

      SIMILAR FAMILIES: Several common spider families on the Pacific coast are similar to the prodidomids, although only Gnaphosidae (p. 156) shares their enlarged anterior lateral spinnerets. On gnaphosids, however, the spinnerets are cylindrical with short spigots, while on the prodidomids they’re...

    • GNAPHOSIDAE Stealthy Ground Spiders
      (pp. 156-166)

      IDENTIFICATION: Stealthy ground spiders are predominately nocturnal, cursorial spiders. They are generally recognizable by the shape and size of their anterior lateral spinnerets, which are widely separated, enlarged, and cylindrical and are often clearly visible when the spider is viewed from above. Additional unifying features include their concave endites with distinct depressions across their ventral surfaces and their posterior median eyes that are often oval, triangular, or elliptical in shape. Like most running spiders, stealthy ground spiders have two claws and claw tufts. They have eight eyes, are entelegyne, and are common across the Pacific coast region. While most genera...

    • SALTICIDAE Jumping Spiders
      (pp. 167-180)

      IDENTIFICATION: With their enlarged anterior median eyes, powerful fore legs, and stocky, often ornately decorated bodies, salticids are among the most easily recognized spiders in North America. Jumping spiders are wandering entelegynes and are common in nearly every habitat, from coastal dunes and deserts to montane forests and suburban gardens.

      SIMILAR FAMILIES: With their unusual morphology and characteristic hunting behaviors, jumping spiders are unlikely to be confused with any other spider.

      PACIFIC COAST FAUNA: Thirty-three genera represented by 119 described and numerous undescribed species. Identifying jumping spiders can be one of the most difficult and most gratifying of arachnological challenges....

    • THOMISIDAE Crab Spiders
      (pp. 180-187)

      IDENTIFICATION: Thomisidae is among the most distinctive spider families in North America. The spiders’ fore legs are stocky and laterigrade, an alignment that angles them so that their spined ventral surfaces face out from the body. Legs I and II are also distinctly longer and stouter than legs III and IV, giving these spiders (especially the females) a rather boxy, crab-like appearance. Thomisids can be found across a wide variety of habitats, including leaf litter, tree trunks, and flower heads, and can range in color from white with vivid splashes of pink and green to mottled brown, red, and gray....

    • PHILODROMIDAE Running Crab Spiders
      (pp. 187-191)

      IDENTIFICATION: The running crab spiders are two-clawed entelegynes and make up an exceptionally abundant family within North America’s spider fauna. The different genera are relatively flat bodied, and their outlines vary from short and round(Titanebo)to long and thin(Tibellus).The running crab spiders’ most distinguishing feature is that leg II is longer, sometimes significantly, than leg I. In most genera, the fore legs are laterigrade. In this alignment, the leg’s spined ventral surface faces outward from the front of the body and allows the spider to more effectively grab struggling prey. Nearly all philodromids also have both claw...

    • SELENOPIDAE Flatties
      (pp. 191-192)

      IDENTIFICATION: Selenopids are dorsoventrally compressed entelegynes with only two eyes in the posterior eye row and six in the anterior eye row, although the most lateral of the anterior eyes are exceptionally small and difficult to see. Selenopid bodies are mottled grayish yellow or brown with dark spotting on the abdomen and carapace. Their legs are heavily banded, armed with numerous large spines, and in a laterigrade arrangement, a position that further magnifies their already flattened appearance.

      SIMILAR FAMILIES: No other regional spider family shares Selenopidae’s unique eye arrangement, although several families are superficially similar in form and habit. The...

    • SPARASSIDAE Giant Crab Spiders
      (pp. 192-195)

      IDENTIFICATION: Giant crab spiders are dorsoventrally flattened spiders whose laterigrade leg arrangement allows them to hide in narrow crevices. They are eight-eyed, two-clawed entelegynes with conspicuous claw tufts and scopulae. Their most distinctive feature is a trilobed extension on the dorsal surface of each metatarsal-tarsal joint that allows the spider to lift the tarsus above the axis of the metatarsus, much like a person resting a forearm on a tabletop can raise the hand at the wrist. Regionally, giant crab spiders range from 6.2 to 48 mm (.24 to 1.89 in.) in length.

      SIMILAR FAMILIES: Spiders in the family Selenopidae...

      (pp. 195-197)

      IDENTIFICATION: Juveniles and adult female homalonychids are among the most distinctive and least conspicuous spiders in North America. Small grains of sand adhere to stiff setae on their abdomens, carapaces, and legs, camouflaging them against the background soil. Although adult males lack this applied camouflage, they can be recognized by the combination of a strongly recurved posterior eye row, a broadly rounded carapace with a W-shaped band along the posterior margin, and a roughly pentagonal abdomen. Homalonychids are eighteyed entelegynes endemic to the deserts of the southwestern United States and northwestern Mexico.

      SIMILAR FAMILIES: With their unusual habits, distinctive body...

      (pp. 197-198)

      IDENTIFICATION: Zorids are small, entelegyne spiders with a straight anterior eye row and a strongly recurved posterior eye row. They are two-clawed, and tibiae I and II are armed with six to eight pairs of long, stout spines on their ventral surfaces.

      SIMILAR FAMILIES: The Zoridae eye arrangement is highly unusual. A similar pattern is shared by the wolf spiders (Lycosidae, p. 223), but lycosids lack the heavily armed fore legs of the Zoridae.

      PACIFIC COAST FAUNA: One genus,Zora, with a single regional species,Zora hespera(pl. 29). The male Z.hesperaaverages around 3 mm (.12 in.) in...

    • DICTYNIDAE Mesh Web Weavers
      (pp. 198-205)

      IDENTIFICATION: Dictynidae is a poorly defined, morphologically diverse family of three-clawed spiders whose members include arboreal, cribellate web weavers as well as ecribellate, cursorial hunters. Additionally, many genera are poorly defined and in desperate need of revision. Based on current knowledge, the specific and sometimes even generic placement of many individuals, especially adult females, is extremely difficult, and in some cases impossible.

      Cribellate mesh web weavers are generally less than 4 mm (.16 in.) in length, have eight eyes (with one very rare exception), and build netlike webs around the tips of dried weeds or in the niches of stone...

      (pp. 205-209)

      IDENTIFICATION: Cybaeidae is a family of three-clawed, entelegyne spiders that is difficult to define. As with the other two members of the Dictynoidea superfamily, Dictynidae (p. 198) and Hahniidae (p. 209), Cybaeidae’s genera have historically been shuffled into and out of several families. While most cybaeids have eight eyes, some have only six and a few are completely eyeless. There are, however, several features that, when looked at as a group, unite Cybaeidae’s dissimilar genera. They have rows of trichobothria on their tarsi and metatarsi that become increasingly longer as they progress toward the distal end of each leg segment....

      (pp. 209-214)

      IDENTIFICATION: The Hahniidae are three-clawed, eight-eyed entelegynes. Like several other spider families, they have rows of trichobothria on their metatarsi and tarsi that increase in length as they progress down each leg segment. As members of the superfamily Dictynoidea (along with Dictynidae, p. 198, and Cybaeidae, p. 205), Hahniidae’s genera have been split apart and regrouped numerous times. As currently recognized, Hahniidae contains two subfamilies, Hahniinae and Cryphoecinae. These subfamilies differ conspicuously in the arrangement of their spinnerets; however, similarities in their reproductive structures led to lumping Cryphoecinae within Hahniidae by Lehtinen (1967), a move that more than 40 years...

      (pp. 214-215)

      IDENTIFICATION: Two very dissimilar genera of Zodariidae live along the Pacific coast. Both are three-clawed, eight-eyed entelegynes with exceptionally large anterior lateral spinnerets and highly reduced posterior spinnerets. Additionally, the genusLuticais distinctive in both habitat and coloration, living only along a narrow strip of Southern California’s coastal dunes and on the Channel Islands.

      SIMILAR FAMILIES: No other spider families share the gross morphological features and habitat preference ofLutica. Some Corinnidae (p. 146) might be mistaken for members of the genusZodarion, but none have its greatly enlarged anterior median eyes and highly procurved posterior eye row.


      (pp. 215-217)

      IDENTIFICATION: Members of the family Tengellidae are ground-dwelling, nocturnal hunters with several features that in combination distinguish them from other entelegyne spiders. All of the Pacific coast genera have a prograde leg arrangement, deep notches on the underside of each trochanter, and a vestigial third claw hidden within the claw tufts. They also have at least five pairs of spines on the ventral surface of each anterior tibia. Tengellids range from 7 to 21 mm (.28 to .83 in.) in length. Their eight small eyes are round and similar in size and occur in two transverse rows. Additionally, their anterior...

    • PISAURIDAE Nursery Web Spiders, Fishing Spiders
      (pp. 217-219)

      IDENTIFICATION: Nursery web spiders are three-clawed, eighteyed entelegynes with deeply notched trochanters, although it is often easier to recognize them by their unusual behaviors than by their anatomy. They are closely tied to ponds and streams where they hunt aquatic invertebrates, small fish, and tadpoles either from the shoreline or directly from the water’s surface. Females carry their large, spherical egg sacs under their bodies, held by their chelicerae and attached to their spinnerets. Close to the time of hatching, the females suspend their egg sacs in protective “nursery webs,” normally built in some nearby vegetation. The region’s Pisauridae range...

    • ZOROPSIDAE False Wolf Spiders
      (pp. 220-220)

      IDENTIFICATION: Zoropsidae is represented on the Pacific coast by a single introduced species, the False Wolf Spider,Zoropsis spinimana. This six-eyed, cribellate spider is easily recognized by its large size (10 to 17 mm, or .39 to .67 in., in length), distinctly patterned body, strongly recurved posterior eye row, and straight anterior eye row. Its carapace is orangish brown with a thin, black V behind its eyes and dark, wavy bands along its sides, while the anterior half of its abdomen is decorated with a dark-brown heart mark. The False Wolf Spider has a divided cribellum, and its calamistrum is...

    • OXYOPIDAE Lynx Spiders
      (pp. 220-223)

      IDENTIFICATION: Lynx spiders are easily recognized three-clawed entelegynes with a unique hexagonal eye arrangement. They also have tapered abdomens and long, thin legs with an impressive array of prominent spines.

      SIMILAR FAMILIES: No other North American spider family shares the lynx spiders’ unique eye arrangement. With their darting manner and willingness to jump when disturbed, they are similar to some jumping spiders (Salticidae, p. 167) but are quickly differentiated by their eye structure and thin, spine-covered legs.

      PACIFIC COAST FAUNA: Three genera with six regional species. The largest of the Oxyopidae are the green lynx spiders (Peucetia viridans,pl. 45)...

    • LYCOSIDAE Wolf Spiders
      (pp. 223-232)

      IDENTIFICATION: Wolf spiders are among the most ubiquitous and easily identified spiders in North America. Except for members of the generaSosippusandGeolycosa,wolf spiders are all cursorial hunters and are common in a wide variety of habitats, including grassy fields, suburban lawns, marshes, forests, coastal dunes, and deserts. Females are especially conspicuous when their egg sacs are attached to their spinnerets and when their bodies are covered with newly hatched young. One of their most distinguishing features is their highly unusual eye arrangement. While their anterior eyes are small and run in a straight line across the front...

    • AGELENIDAE Funnel Web Weavers, Grass Spiders (Agelenopsis)
      (pp. 232-237)

      IDENTIFICATION: Although funnel web weavers themselves are generally inconspicuous, their webs are often a prominent part of the summer landscape, especially in grassy fields, on shrubs, and in the corners of old buildings. Agelenids build webs that combine a flat sheet with a tubelike retreat at one corner, earning them their common name, funnel web weavers. They are eight-eyed entelegynes, and in every genus butTegenaria,the eye rows are strongly procurved. Their posterior spinnerets are fairly long, often extending past the spiders’ abdomens, and under magnification, a peppering of plumose hairs can be seen on their legs and bodies....

    • AMAUROBIIDAE Hacklemesh Weavers
      (pp. 237-241)

      IDENTIFICATION: The hacklemesh weavers are secretive, nocturnal spiders whose fairly distinctive webs consist of collars of tangled, bluish-gray cribellate silk radiating from protected crevices. Nearly every hacklemesh weaver has eight eyes in two transverse rows (the exception being one uncommon, minute California species) and a divided cribellum. Amaurobiidae are generally robust spiders with relatively thick legs, ranging from 1.3 to 22 mm (.05 to .87 in.) in length. Other defining features of the family include a calamistrum that is never more than half the length of metatarsus IV, rows of trichobothria on the tarsi and metatarsi that increase in length...

      (pp. 241-243)

      IDENTIFICATION: Titanoecidae is a small family of eight-eyed, cribellate spiders. Because of their similarity to some of the region’s other cribellate families, several morphological features must be used in conjunction to confirm a titanoecid’s identity. Their endites are nearly parallel, and their cribella are longitudinally divided into two adjacent oval plates. While female titanoecids have calamistra that extend nearly the entire length of their fourth metatarsi, on males the calamistra are either vestigial or lacking entirely. They have numerous leg spines but lack long, conspicuous trichobothria. The region’s Titanoecidae range in size from 4.5 to 8 mm (.18 to .31...

      (pp. 243-244)

      IDENTIFICATION: The Pacific coast’s only Desidae species is the introduced Gray House Spider,Badumna longinqua. It is locally common, synanthropic spider that has a divided cribellum and anterior median eyes that are larger than the others. is purplish brown with a gray abdomen and builds very distinctive lattice-like cribellate webs.

      SIMILAR FAMILIES: The Gray House Spider was initially thought to be a hacklemesh weaver (Amaurobiidae, p. 237), but its coloration, unusual web, and large anterior median eyes all stand in contrast to those of the native Amaurobiidae.

      PACIFIC COAST FAUNA: One genus containing a single introduced species. The Gray House...

      (pp. 244-246)

      IDENTIFICATION: The region’s only amphinectid,Metaltella simoni,is a cribellate, eight-eyed, three-clawed entelegyne whose most diagnostic feature is its dentition. It is the only cribellate spider in North America with five or more teeth on each cheliceral margin. It is also exceptionally common around homes with well-watered lawns and gardens across a large portion of Southern California.

      SIMILAR FAMILIES: Amphinectidae is most similar to the families Amaurobiidae (p. 237) and Titanoecidae (p. 241). All three families share numerous features, including a divided cribellum, and Amphinectidae and Amaurobiidae share a relatively short calamistrum. However, neither Amaurobiidae nor Titanoecidae ever have more...

    (pp. 247-252)
    (pp. 253-256)
    (pp. 257-286)
  9. INDEX
    (pp. 287-304)
  10. Back Matter
    (pp. 305-307)