EUROPEAN HOUSE SPIDERS

AND OTHER

FUNNEL WEB WEAVERS

Closely related to the hobo spider, Tegenaria agrestis, most other members of the genus Tegenaria are considered as a group to be European House Spiders. Two of these, the domestic or lesser house spider, Tegenaria domestica, and the giant or larger house spider, Tegenaria gigantea, share much of the North American range of the hobo spider. Other members of the spider family Agelenidae are found within the range of the hobo spider as well, most significantly several species of grass spider, Agelenopsis spp.. Because of their familial relationship, all of the above spider species share traits and characteritics that make them important competitors against the hobo spider. Non-hobo agelenid spiders are also important as "look-alike" species to the hobo. Some species are very difficult for the untrained eye to distinguish from the hobo spider, and many non-arachnologist "hobo spider" identifications ultimately turn out to be other Tegenaria species or other members of the family Agelenidae.

Tegenaria domestica is found throughout the entire North American range of the hobo spider, and most probably throughout the European range of agrestis as well. While generally considered a "city dweller", domestica is also common in and around buildings in some rural areas of North America. Like the hobo spider, the domestic house spider is indigenous to Europe, but was transported to North America and other continents by humans, almost certainly by means of ocean vessels: The approximate date of the original North American introduction of T. domestica is unclear, but it probably occurred very early, perhaps in conjunction with the first arrival of significant numbers of humans from Europe. Since then, this spider has become established almost universally in North America and other continents. Domestic house spiders are very easy to mistake for small hobo spiders; The herringbone or broken chevron pattern on the dorsal abdomen (which is obscured in darker specimens) is similar in both species, but domestica is smaller (12 mm) than agrestis. Coloration of the domestic house spider varies from greyish-brown to dark chocolate brown: Most domestica appear at first glance as smaller, darker spider than the adult hobo spider. The legs of the domestic house spider are ringed (see photograph at right), unlike the ringless legs of the hobo spider and the giant house spider. Leg rings can be difficult to see in some specimens, but can usually be visualized by placing the spider to be examined in a "zip-lock" baggie and looking at the legs through a strong light source. In the northwestern U.S. Tegenaria domestica exemplifies one of many spider species with leg rings, all of which are harmless and beneficial. Another discernable difference between the domestic house and the hobo spider is the pattern found on the sternum (breast plate): The sternal pattern of the hobo spider consists of a light colored center, with dark vertical bands on the sides; the sternal plate of the domestic house spider consists of a light colored center, with three small circles in a vertical line on the sides. As with all spiders, positive identification of this species requires examination of the genitalia, and should be left to a specialist.

Domestic house spiders are major food competitors of the hobo spider and compete for web sites as well. In southern Idaho, domestica often lives colonially in crawl spaces beneath homes in rural areas. These colonies may consist of 30 to 100 or more specimens which construct webs in the floor joints and corners, as well as in storage boxes, bottles and other objects being stored in the space. As domestic house spiders are not seasonal (unlike T. agrestis and T. gigantea), these colonies are active year-round. The presence of large T. domestica colonies in the crawl spaces of rural homes virtually guarantees the relative absence of hobo spiders in such homes. As hobo spiders are noticeably absent from the premises of most buildings with large domestica colonies, yet are present in similar habitats where domestica has not established colonies, the domestic house spider can be exemplified as a competitor which can successfully prevent the invasion of hobo spiders by the principle of competitive exclusion. Domestic house spider colonization should be encouraged in rural areas within the North American range of the hobo spider; destroying domestica colonies with sprays, bug bombs etc. in such areas is extremely foolish, and is an open invitation for subsequent invasion by the hobo spider.

Tegenaria domestica may also play a predatory role in the natural control of hobo spider populations. Adult hobo spiders are larger and more robust than adult domestic house spiders, and thus are not likely candidates for domestica predation, but sub-adult hobos, particularly first year spiderlings, are at risk of predation by adult domestica.

Tegenaria gigantea, the giant or larger house spider (pictured above), is a larger cousin of the hobo spider, T. agrestis, and is in fact the largest member of the genus Tegenaria. Like the hobo and domestic house spiders, gigantea was introduced into North America from Europe; It probably was first introduced on Vancouver Island, B.C. in the mid-1920s, and was likely present in the Seattle area by 1960. The giant house spider has gained a reputation and received much publicity over the past several years as a beneficial spider which keeps hobo spiders out of houses; this reputation seems well founded: In much of western Europe (England, France, Germany and Wales) where agrestis lives in fields , virtually divorced from the human population, gigantea is commonly found inside houses and other buildings. In some areas of the northwestern United States (parts of the Seattle, WA area for example), the establishment of gigantea populations appears to correlate with a reduction in the numbers of hobo spiders.

T. gigantea superficially looks very much like T. agrestis, and smaller specimens are difficult to distinguish by eye-balling even to the arachnologist. Adult gigantea are larger (16-18mm body length) than agrestis, with proportionally longer legs which are not ringed or banded. The brownish coloration is almost identical for the two species; only the wider, darker margins of the cephalothorax in gigantea distinguish it from agrestis when viewed from a dorsal perspective. The sternum (breast plate) of gigantea is similar to that of T. domestica, exhibiting a pale center, with four small circles in vertical lines on each side, rather than the solid dark margins of agrestis.

Behaviorally, the giant house spider shares some common traits with the hobo spider, but differs in some other key traits. Like agrestis, gigantea can move quickly, and in fact, until 1987, was listed (under the name Tegenaria atrica) as being the world's "fastest" spider in the Guinness Book of World Records, having been clocked at speeds of up to 1.73 ft/sec (1.17 mph) on a level surface; that honor has now been officially awarded to certain African and Middle Eastern "sun spiders" or solifugids, which are really not spiders at all. Unlike agrestis, which prefers to remain at or near ground level, gigantea has no aversion to heights, often being sighted in lofty areas such as atop curtain cornices, or on other high ledges inside houses (such as the specimen pictured at left, near the ceiling of a Seattle area laundry room). Adult hobo spider and giant house spider males both wander in search of mates in the late summer and early fall; this undoubtedly leads to occasional meeting and confrontation. The giant house spider, being a larger carnivorous arachnid than the hobo spider, very likely preys upon the hobo when the opportunity presents itself, but it's primary role as an agent of competitive exclusion appears to be as a competitor for food and web sites. It is noteworthy that specimens and webs of Tegenaria gigantea are often found beneath the same objects as specimens and webs of T. agrestis, although their respective webs are usually widely separated; Specimens of T. domestica are sometimes found co-existing beneath debris with these two species as well.

The migration and establishment of giant house spider populations into southern Idaho, northern Utah, and other areas of the upper Great Basin desert has been anticipated and awaited by many as a key to eliminating hobo spider populations. Observations now suggest that gigantea establishment in these areas is unlikely: While gigantea has extended it's North American range eastward and northward from western Washington (specimens have been found as far east as Saskatchewan, Canada), it does not appear to be establishing itself in the more arid, southerly regions within the range of the hobo spider. In these areas Steatoda spiders, particularly Steatoda hespera, appear to be the principal arachnid competitor/predator of T. agrestis.

Agelenopsis grass spiders are found throughout the North American range of the hobo spider. In some locales these spiders are very common and can be found on the same premises as the hobo spider: In other areas, such as the heavily infested Upper Snake River Valley of Idaho, it appears that the hobo spider has displaced the urban grass spider population; grass spiders in this region are found commonly in rural areas where the hobo spider has not become established, but are rare or absent in cities and towns where the hobo is the dominant agelenid spider. Grass spiders compete with the hobo spider for food and for web sites, and may take hobo spiders as prey in some circumstances. The noteable absence of Agelenopsis species in areas with large agrestis populations however, strongly suggests that the grass spiders are in many areas, on the losing end of the competitive race with the hobo spider.


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