Common Name: Spider – Hobo spider
Latin Name: Tegenaria agrestis
Common Family Name: Funnel web spiders
Latin Family Name: Agelenidae
Other Names: Aggressive house spider, funnel weavers, domestic house spider
Origin: At least 7 species of spiders in the genus Tegenaria occur in North America, with only T. chiricahuae a native, and occurring in Arizona and New Mexico. The other six species are believed to be European in origin, with T. domestica found throughout the U.S. and T. agrestis found in the Pacific Northwest states. The family contains many other genera and over 400 species of spiders.
Biology: The most notorious species in this group is T. agrestis, variously called the Aggressive House Spider or Hobo Spider, and it is known to bite with little provocation. Like many spiders it has venom which is cyto-toxic, and tissue death at the site of the bite, leading to a lingering open wound, is very possible. It is a very common spider in structures in the Pacific Northwest, and is the most likely cause of serious spider bites there. Species of Tegenaria usually live about two years, and with T. agrestis the first year is spent developing to the adult stage, the second summer is for mating and egg production, and the adults die shortly after this. The family name is derived from the prey capture habit of these spiders, which create wide mat of webbing with a funnel-like hole in it, and the spider waits within this funnel for prey to stumble onto the web mat. The spider then rushes out, subdues the prey, and drags it back into the funnel for feeding. The funnel-web mats may be on vegetation or near the soil, or possibly within structures in undisturbed areas.
Identification: Since Tegenaria appears to be the most important group of spiders in this family the description will be for them. These are fairly large spiders, with adult bodies about ¾ inch long and with very long, hairy legs. There are several longitudinal dark stripes on the top of the cephalothorax and the top of the abdomen exhibits a distinct “herring-bone” pattern of darker, zig-zag lines. There are eight eyes in Tegenaria, arranged in two rows across the front of the “face” area, and with the posterior row strongly curved to the back, and the outer pairs of eyes nearly touching.
Characteristics Important in Control: Since these spiders pose a definite human health threat they do need to be controlled when found living in structures. Habitat modification, to remove all possible harborage sites, is a vital component of control of this group. Exterior vegetation should be trimmed well away from the structure, grassy areas kept mowed, and piles of lumber or firewood maintained properly and well away from the building. Any unnecessary objects on the soil need to be removed. On the interior cleanup of clutter is important, along with physical removal of webbing. Exclusion techniques need to be employed to close any potential gaps or holes the spiders may use to enter the building. Chemical applications include the use of a dust insecticide within cracks and voids that may harbor the spiders, as well as an application of a residual pyrethroid insecticide around the exterior and to likely spider areas inside.