Brown House Spiders

General Facts

Steatoda grossa is also known as the brown house spider, the cupboard spider, the dark comb-footed spider and the false black widow. As one of its common names suggests, this spider resembles the black widow spider.

Scientific Name

Steatoda grossa

Appearance

Similar to the true black widow, the brown house spider female is about ¼ to 3/8 inch in length (does not include the length of the legs), but does not have the characteristic red hourglass pattern on the underside of the abdomen. Also, this spider is more oval in shape than the true black widow. In most cases, the abdomen is purplish-brown to black with pale yellow to grayish markings, and the cephalothorax is a red-brown color with slightly darker legs. Brown house spiders have long, thin legs that are dark brown or black for the adult females and light brown or reddish for the adult males.

Behavior, Diet & Habit

Brown house spiders are very common in man-made structures and are also found outdoors in sheltered places including in tree bark, wood piles, under rocks, on low-growing foliage and in outdoor storage buildings. When found indoors, they usually build their webs near the ground-level floors, but also may build inside cupboards and cabinets and can be found more or less throughout the year.

Similar to most other spiders, this species preys on insects and other spiders. The brown house spider may prey on black widow spiders, though pill bugs make up a good portion of its diet. Males die shortly after mating and live for only 12-18 months. Females live up to six years.

Both the brown house spiders and true black widow spiders suspend upside down in their web, making it somewhat easy to spot the presence or absence of the red hourglass on the abdomen. Both are nocturnal.

Reproduction

Brown house spiders mate in the spring with females producing 2 or 3 egg cases every few months. Each sac contains 10-250 eggs. After hatching, spiderlings go through two molts and then leave the egg sac.

Signs Of An Infestation

The presence of the spiders, their egg sacs, webs and the appearance of dead prey are evidence of brown house spiders living inside the home.

Distribution

The brown house spider originated in Europe, but can be found worldwide. Within the United States, its wide distribution includes many areas around the Atlantic, Gulf, and Pacific regions and the southern and western states.

More Information

Sealing all cracks, gaps and crevices that provide access inside the home is an important way to prevent spiders from wandering into the structure. Another preventive method is to use a vacuum or broom to remove spiders, webs and egg cases. Finally, make sure the insects that serve as the brown house spider’s food source are kept to a minimum and harborage sites are removed and cleaned up.

Should the homeowner need help controlling the brown house spider or any other spiders, contact your pest management professional and request an inspection. Your pest management professional can use his or her inspection findings to prepare a comprehensive pest management plan that will effectively and efficiently deal with the specific pest problem.

Brown house spider bites produce symptoms that are similar, but much less serious than a black widow bite. In some instances, brown house spider bites may cause blisters around the bite and can include moderate to severe pain plus mild to moderate nausea, headache and lethargy. Symptoms normally last from 1-60 hours unless the bite victim is allergic to the spider’s venom.