The Hobo Spider (Tegenaria agrestis) is a species of arachnid that is native to western and central Europe. It is now also found in the northwestern United States and southwestern Canada. It has recently spread into southern Alaska, making it the first dangerous spider to humans in that state. It has been also recorded on a small island (Peberholm) in Denmark, and in southern Sweden. Its habitat is semi-arid and warm environments, although in Europe it is not normally encountered in houses, mostly due to compost. Hobo spiders are most problematic during the months of August and September, especially west of the Cascades.
The adult female is about 0.43 to 0.59 inches long. The male is generally smaller and grows to about 0.43 inches. The coloring of both sexes is a mixture of soft brown or rusty earth tones. Although most spiders of the genus Tegenaria have hairy-looking legs, the legs of the Hobo Spider are mostly smooth and solid light-brown in color.
The web is flat or curved with a sheet of dense silk that curves upwards at the edges. The web slants downward to one corner where it forms a funnel-like retreat for the spider to rest in. There is an escape hole in the back as well. The web catches prey that falls into it from above, and insects that fall into it become tangled in the trip threads that cover the surface of the web – the web itself is not sticky. Though this is an aggressive spider, it will usually avoid contact with humans. Most bites occur through accidental touching, squeezing or pinching of the spider or web area. The venom of the Hobo Spider is strong enough to cause intense pain at the site of the bite and may also lead to tissue death of the affected area, though this is not confirmed.
The aggressiveness of the Hobo Spider is found to be more true when the female is tending to her egg sac, becoming very aggressive if it feels the egg sac is being threatened. However, they normally do not bite unless forced to protect themselves, and in most cases, it does not inject venom when it does bite. When a Hobo Spider does inject its venom, it is not likely that the bite will be fatal, especially in healthy humans. Some reported symptoms of the bite include intense headaches, vision problems, and feelings of malaise or nausea. These symptoms are not confirmed for the Hobo Spider due to lack of positive identification of the spider.
The best protection against Hobo Spiders in one’s home is the presence of other spiders, especially the Giant House Spider (Tegenaria duellica), that will compete with them for food and often kill them if confronted. Care should be exercised when disturbing webs or moving boxes around. Though this species does not perceive humans as prey, it is possible for them to bite if they feel threatened. The best way to remove webs is by gently sweeping it away with a broom. Most spiders will generally follow suit and leave as quickly as possible when disturbed.