[Pest Profile] Yellow Sac Spider

Order/Family: Araneae/Clubionidae
Scientific Name: Cheiracanthium spp.

Description
The bodies of female sac spiders are about 3/16-inch to 3/8-inch long and either pale yellow to pale green or orange brown to red. Males are smaller than the females, being 1/8-inch to 5/16-inch long.

Biology
Sac spiders lay their eggs in a loose mass covered with a thin white silk sac. Eggs often are laid in indoor retreats and are guarded by the female; however, eggs can be found outdoors in rolled leaves. Females produce several egg masses during their lifetimes, each containing 30 to 48 eggs.

Habits
Sac spiders are of medical importance because, as a group, they are more responsible than any other species for spider bites in the United States, but bites often go unreported because the spider goes unseen or the bite is not felt. Most bites occur when the spider crawls into clothing and is pressed close to the skin. In most cases, the bite produces no more than localized redness, slight swelling and a burning sensation. Sac spiders are commonly found indoors. Their numbers increase significantly in the fall when the weather turns cool and their food supply disappears. They enter structures through faulty screens, cracks around doors and windows, and gaps around pipes, wires and vents. If food is available, they enter and remain in wall voids and crawlspaces. They build silk retreats in upper corners and the joints between walls and ceilings indoors and remain in them during the day. Outdoors, they are found among rocks and wood piles, under decks and benches, around window and door frames, under roof eaves and soffits, behind shutters, and in other protected areas. They are also found on tall grass, weeds, and leaf litter.

Control
Areas conducive to spider activity, such as dark protected areas that attract insect prey, should be identified. Clutter and debris inside structures and scrap lumber, woodpiles, rocks, landscape timbers, and other protective outdoor materials should be removed. Both indoors and out, a vacuum cleaner with a crack and crevice attachment should be used to remove spiders, sacs and egg sacs; then the bag should be sealed and discarded immediately. Particular attention should be paid to upper corners. Trees and bushes should be trimmed back so they do not contact the structure, and the grass should be mowed. Pesticides can be applied as residual sprays or dusts with special emphasis on harborage areas. Nonresidual aerosols, mists and ULVs containing a pyrethroid insecticide can be used to kill exposed spiders. Dusting hollow block voids along the sill plate might be useful in reducing indoor populations. Pesticides are more effective in eliminating the spiders’ food, i.e., insects, than killing the spiders.