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The hobo spider, Tegenaria agrestis, is a member of the family of spiders known as the Agelenidae or funnel web weavers. Approximately 500 species of funnel web weavers occur worldwide; about 300 of these are found in North America, and about 100 species are native to Europe. Funnel web weavers are characterized by their ability to move rapidly, and by their layered, flat web, which has a funnel-like lair at the rear in which the spider resides and waits for prey. The web is not sticky like that of many spiders, but rather is a trip web, which traps insect prey that is unable to navigate on the surface.
The genus Tegenaria contains those spiders which are commonly known as European house spiders, although not all are European, and some do not live in houses; about 90 species are recognized. Some species of European Tegenaria have extended their range far beyond the European continent: The domestic or lesser house spider, Tegenaria domestica, is now cosmopolitan, and is common in and around human habitations in many areas of the world. In the United States the giant house spider, Tegenaria gigantea, is now found in the Pacific Northwest, and Tegenaria pagana is now established in some southern and western states.
Tegenaria agrestis, the hobo spider, was first described in 1802 by naturalist C.A. Walkenaer, in the Paris based journal Faune Parisienne, (vol. 2, pp. 187), under the name Aranea agrestis, which translates spider of the field. This reference to the field was accurate for the species in its indigenous range (western Europe), where the spider lives in fields, woods and rock quarries. While in Europe the hobo spider is occasionally found in greenhouses, it is largely divorced from the human population on that continent.
The hobo spider was first reported in the U.S. in 1936 by arachnologist Harriet Exline (as Tegenaria magnacava), who published her findings in the journal Psyche, vol. 43(1), pp. 21-26. In the United States, the introduced hobo spider did not seek the same type of habitat favored by its European counterpart: Rather, it became established around human habitations, and is now commonly found around the foundations of houses, and beneath rocks, wood, and ornaments in yards. Recently, U.S. specimens of hobo spider have been found in rural areas, including some heavily farmed areas; this trend may continue, placing some U.S. populations of this spider in habitats similar to those that it occupies in Europe. It is unlikely that this trend will affect populations in urban areas. Urban populations of hobo spider do appear to be decreasing in some areas, such as Seattle, Washington, where the giant house spider, Tegenaria gigantea, has become abundant.
The life cycle of the hobo spider in the United States has not been conclusively established, as controlled laboratory studies on this topic have not been reported. Some arachnologists believe that west coast populations are annuals, completing the entire life cycle in one year. Inland populations were originally reported in the literature to undergo a two year life cycle; however, three distinct stages (small juveniles, medium sized immatures, and adults) can be found during the late summer and early fall in inland areas, suggesting that inland populations may actually have a life cycle of three years. The eggs of the hobo are deposited in one to four egg cases in late September and October. These egg cases are composed of several layers of silk, intermingled with layers of soil and debris. The egg cases are usually attached to the undersides of rocks, wood, or other items found in yards, gardens and vacant lots; each egg case may contain 100 or more eggs. Contrary to some references hobo spiders are not prone to construct egg cases inside living quarters (though they have been found in crawlspaces). The eggs hatch in early to mid-June: The spiderlings emerge, feed, and largely remain beneath the surface during their first season, molting their exoskeleton periodically as they grow. The juvenile spiders then overwinter, and are sometimes found indoors during this period. Assuming the two year scenario, the spiders emerge as adults in late July to early August of the second year. The females build webs and remain stationary, but the males began nocturnal wanderings in search of mates. It is at this juncture that males enter houses (often in large numbers) from outside habitat and from garages and crawl spaces; thus, they come into contact with humans; most bites occur during this time period. The hobo spider season peaks during the first week or two of September in most areas. After mating the males began to die, and are absent by the first week of October. The females construct the egg cases, and most remain in the web until they die, usually expiring by mid-November: Some adult females do enter houses in late September, October, and November.
The behavioral aspects of the hobo spider have been a subject of controversy in the past, primarily due to the the publicized myth of the "aggressive house spider". While the hobo will bite when pressed against skin or tormented, it is no more "aggressive" than other wandering spiders; it does not bite without clear provocation, and certainly does not track people down and attack them, as some people have come to believe. The quick movements of this spider, and the fact that they sometimes run toward individuals when disturbed have fueled such myths, but the idea that such spiders are "attacking" is a misinterpretation. In actuality, these spiders have very poor vision and cannot distinguish objects more than a foot or two away. When disturbed inside a house, particularly when a light has just been turned on, the spiders most often remain stationary. When such spiders finally sense potential danger, they run, sometimes toward a person that they really can't see. Hobo spiders are not good climbers, and are usually found at ground or basement level. They sometimes climb up to a level of about four feet if the surface of the wall, etc. is sufficiently porous. Hobo spiders found in wash basins and bathtubs arrived there by falling down the slick porcelain surface; they did not come up through the drain.
Physically, the adult hobo spider is a moderately large (12-18 mm body length) brown spider, with long, unmarked legs (legs included, a typical specimen would fit nicely on a silver dollar). The dorsal abdomen exhibits a "herringbone" or multiple chevron pattern, which may be quite obscure in darker individuals. The male sports two pedipalps (antennae like protuberances) between the two front legs, which are swollen at the ends, looking somewhat like a pair of boxing gloves; these "boxing gloves" are actually the male genitalia, not "fangs" or "poison sacs". The female generally has a larger abdomen than the male, and does not have swollen "boxing gloves" at the ends of the pedipalps. Several other spiders resemble hobo spiders; only an arachnologist, or other specifically trained person should attempt to make a positive identification of this species: In an instance where a spider has bitten a person, it is imperative to obtain positive identication only from a qualified professional arachnologist.
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