The House Spider
Common Name: House/American House/Domestic Spiders Scientific Name: Achaearanea Tepidariorum (C.L. Koch) Class/Order/Family: Arachnida/Araneae/Therididae Metamorphosis: Simple
INTRODUCTION
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.
RECOGNITION
Adult female body length about 3/16-5/16" (5-8 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 (=chevronsP'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 rowlcomb of serrated bristles on venter; all tarsi with 3 claws each.
SIMILAR GROUPS
- Other Achaearanea spp. lack chevrons on abdomen.
- 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.
BIOLOGY
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 may produce up to 17 sacs, containing over 3,760 eggs, in her lifetime. The sacs are 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 lst instar spiderlings remain in the sac until they molt once. The 2nd instar spiderlings 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.
HABITS
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. Eventually, successful webs are constructed where air currents bring in prey. 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, house 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 saves especially near light sources which attract prey.
Because of their web site selection by trial 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.