Yellow Sac Spider

yellowsac_spider

Overview

Spiders have two body regions; the cephalothorax (the first body section with head and legs), and abdomen. All spiders also have 4 pairs of legs, fangs and venom, 6 or 8 eyes* and the ability to make silk. Spiders do not have antennae, but their short first pair of legs (called pedipalps) may superficially look like antennae. One difference among spider groups is in the manner of prey capture. The most familiar web spinner spider capture technique is to spin a silk web, and wait and pounce on prey, usually insects, after they are caught in the web. Another group of spiders actively hunts down their prey. Prey is grabbed with the fangs and injected with venom, and silk may be used to subdue the prey. Most of the venomous spiders in the United States do not spin large complex webs; instead they depend on strong venom to incapacitate prey. Of the 3,000 or more spiders in the United States, only a few enter homes on a regular basis.

Identification

Family Miturgidae Cheiracanthium mildei Normally found indoors behind curtains, along ceilings and upper portions of walls, often hides under clutter or in cracks during the day. The abdomen is a shade of pale yellow, and the sac spider may superficially resemble a brown recluse in size and shape. Actively hunts at night and makes a white tubular retreat (the sac) which may be found indoors with our without the spider. Cheiracanthium spiders can be responsible for a very painful bite that may create an area of dead skin.

Family Clubionidae Sac spiders or two-clawed hunting spiders Trachelas tranquillus T. tranquillus is another of the sac spiders that may be found in homes. It ranges from New England and adjacent Canada, south to Georgia and Alabama and west to Kansas and Minnesota. Outdoors, they are found in the same places as yellow sac spiders (see above) and also construct silken retreats, within which they hide diurnally. Most occurrences of T. tranquillus in homes coincide with falling temperatures in autumn. They do not, as a rule, establish reproducing colonies in homes.

The female is 7-10 mm in length; the male is 5-6 mm. The chelicerae and carapace are thick, hard, and reddish-brown, covered with what appear to be tiny punctures. The abdomen is pale yellow to light gray, with a slightly darker dorsal stripe. The front pair of legs is darker and thicker; the other three pairs become increasingly lighter and thinner toward the last pair.

Biology

These small hunting spiders rest during the day behind curtains, in closets, under shelves and in dark corners. During the night they hunt insect prey and roam over surfaces in search of victims. These spiders prefer warmer and drier habitats. They can be found at the bases of plants, on fences, inside rolled leaves, and under stones and boards. Mature females are often collected while they wander about in homes during the autumn. Males mature and mate in midsummer, and each female will deposit a pure white egg sac containing 30-50 eggs in September or October. A common oviposition site is under loose tree bark. A peculiar trait of this spider is its reported tendency to scavenge on dead spiders and insects.

Control

You can use sticky insect traps to caputre spiders as they hunt throughout a room. Place traps at floor corners to improve encounter rates with spiders.

Chemical sprays will have limited if any value.

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