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Common Spiders of North America$

Richard A. Bradley

Print publication date: 2012

Print ISBN-13: 9780520274884

Published to California Scholarship Online: May 2013

DOI: 10.1525/california/9780520274884.001.0001

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FAMILY NESTICIDAE • Cave Cobweb Spiders

FAMILY NESTICIDAE • Cave Cobweb Spiders

Chapter:
FAMILY NESTICIDAE • Cave Cobweb Spiders
Source:
Common Spiders of North America
Author(s):

Richard A. Bradley

Publisher:
University of California Press

The cave cobweb spiders of the family Nesticidae are similar in appearance to cobweb weavers (Theridiidae) but are usually limited to caves or cavelike environments. Like the cobweb weavers, these spiders possess a comb of curved serrated bristles on their fourth tarsi. These diagnostic features are not readily visible without a dissecting microscope. Members of both families attack by wrapping their prey with sticky silk. Unlike most theridiids, cave spider females typically carry their egg cases with their chelicerae or attached to their spinnerets. There are more than 200 species worldwide, and 38 species are known from North America north of Mexico. Some of the species that are restricted to caves have become pale and lost their eyes.

Eidmannella Pallida (Emerton, 1875)

Plate 24

Identification

This is a small pale spider. Some individuals of this variable spider, such as the one illustrated in Plate 24, are pale and unmarked. Others show a dusky edge to the carapace, at the edges of the head region, and around the eyes. In a few populations the abdomen has dark chevron markings. Individuals in some cave populations have reduced eyes or no eyes.

Occurrence

This species is widespread in North America. Most records are for the East. They have been found in dark places, under rocks, and in caves.

Seasonality

Adults: all year.

Remarks

The female is often found near the egg sac, presumably guarding it. Sometimes she has been observed carrying it attached to her spinnerets.

(p.170) Nesticus Silvestrii Fage, 1929

Plate 24

Identification

This is a small variable spider. Some individuals have dusky markings as illustrated. Other individuals are uniformly pale. Individuals in some cave populations have much longer legs.

Occurrence

This is a western species. There are similar species in this genus throughout the East. This species occurs from British Columbia south to central California. They have been found in dark areas, under rocks, among tree roots, and in caves.

Seasonality

Adults: all year.

Remarks

A related species (Nesticus cellulanus) has been introduced into North America, where it has occasionally been found in buildings.