Common Name: House / American House / Domestic Spider
Scientific Name: Achaearanea tepidariorum (C. L. Koch)
The common names reflect the fact that this is usually the spider most often encountered indoors. It is a nuisance pest, probably more because of its webs than the spider itself. This spider is found worldwide and is common throughout the United States and Canada.
Adult female body length about 3/16-5/16″ (508 mm) including an almost spherical abdomen, male body length about 1/8-3/16″ (3.8-4.7 mm) including an elongated abdomen. Color highly variable with carapace (cephalothorax dorsum) yellowish brown; abdomen dirty white with a few dark spots (sometimes with a black triangular spot in center of dorsum) to almost black, with several dark stripes meeting at angle medially (=chevrons/”army sergeant stripes”) above tip of abdomen; legs orange in male but yellow in female, with dusky ring at end of each segment (=banded). With 8 eyes, 2 lateral pairs almost touching. Last tarsal segment of 4th pair of legs with row/comb of serrated bristles on venter; all tarsi with 3 claws each.
(1) Other Achaearanea spp. Lack chevrons on abdomen.
(2) Other spiders lack comb of serrated bristles on last tarsal segment of 4th pair of legs and 8 eyes with 2 lateral pairs almost touching.
Female house spiders lay about 250 eggs (range 132-442) in a silken sac which is brownish, oval to flask-shaped, about 1/4-3/8″ (6-9 mm) in diameter, and with a tough, papery cover. There may be more than one sac in the web at a time; a female usually located in the center of the web but may be moved to warmer or cooler sites as required.
The eggs hatch in about 7-10 days but the 1st instar spider lings remain in the sac until they molt once. The 2nd instar spider lings then emerge and balloon. Females molt 7 times and males 6 or 7 times to reach maturity. Adults may live for a year or more.
The house spider randomly selects its web sites. If a web does not yield prey (food) it is abandoned, another site is selected, and a new web built. Survival is low in modern homes with low humidity and few insects, higher in garages, sheds, barns, warehouses, etc. because of more prey and generally higher humidity, and highest outdoors in protected places. Inside structures, houses spiders are most likely to be found in upper corners, under furniture, in closets, angles of window frames, basements, garages, and crawl spaces.
In warehouses, they are common in corners near doors that stay open. Outside, they are often around windows and under eaves especially near light sources which attract prey. Because of their web site selection by trail and error, many webs may be constructed in several days. Dust collecting on these webs accentuates their presence. This situation is unacceptable in most households, offices, food processing plants, etc.
Follow the standard control procedures for spiders as outlined in the introductory section. Use a vacuum to remove adults, egg sacs, and webs. If a broom is used, adults usually escape unless they are first individually treated with a nonresidual contact pesticide; this can leave marks or dirt/dust on wall and ceiling surfaces.