Giant house spider
|Giant house spider|
C. L. Koch, 1843
The giant house spider, Eratigena atrica (atri - dark, feral, from atrium) is one of the biggest spiders of Central and Northern Europe. It has also been known by the names Tegenaria duellica or T. gigantea; it is a member of the recently described genus Eratigena and is a close relative of both the domestic house spider and the infamous hobo spider. The bite of this species does not pose a threat to humans or pets, and is generally reluctant to bite, preferring to escape.
The two sexes do not differ in coloration or markings. Its coloration is mainly dark brown. On its sternum is a lighter marking, with three light spots on each side. The opisthosoma features a lighter middle line with six "spots" on each side. The Giant house spider has the same coloration as the Domestic house spider; it has earthy tones of brown and muddy red or yellow. They also have conspicuously hairy legs, palps and abdomen. In contrast to other related species, E. atrica and the smaller E. picta have uniformly colored legs. In other species, the legs are annulated or spotted. Female body size can reach 18.5 millimetres (0.73 in) in length (despite its name, smaller than Tegenaria parietina), with males having a slightly smaller body at around 12 to 15 millimetres (0.47 to 0.59 in) in length. The female leg span is typically around 45 millimetres (1.8 in). The leg span of the male is highly variable, with spans between 25 to 75 millimetres (0.98 to 2.95 in) being common.
Its eight eyes are of equal size and are arranged in two rows. As the eyes contain fewer than 400 visual cells, T. atrica can probably only distinguish light and dark.
The giant house spider is indigenous to north western Europe. However, it was unwittingly introduced to the Pacific Northwest of North America circa 1900 due to human activity and strongly increased in numbers for the last century. Its original habitat consists mostly of caves, or dry forests where it is found under rocks, but is a common spider in people's homes.
The webs built by the giant house spider are flat and messy with a funnel at one end. The spider lurks in the funnel until a small invertebrate happens to get trapped in the web, at which point the spider runs out and attacks it. They usually build their webs in corners (on both the floor and ceiling), between boxes in basements, behind cupboards, in attics, or any other area that is rarely disturbed by large animals, or humans. Often found near window openings.
Biology and behavior
T. atrica often builds its funnel web in undisturbed corners. The web does not contain glue, and if an animal gets entangled in the web, the spider runs towards it, crushes the animal to a pulp, which is then digested.
T. atrica normally lives for two or three years, but lifetimes of up to six years have been observed. While the female only leaves its nest to feed, males can often be seen wandering around houses during the late summer and early autumn looking for a mate. Males can be found from July to October, adult females occur all year.
At least 60 spiderlings emerge from an egg sac. Unusual for spiders, they are subsocial at this stage: they remain together for about a month, but do not cooperate in prey capture. The amount of cannibalism correlates with the amount of available food. T. atrica molts seven or eight times before reaching the immature adult state, and after a final molt reaches maturity.
Like most spiders, the spider possesses venom to subdue its prey. Since E. atrica bites can penetrate human skin on occasion, the effects of agatoxin might be felt by bite victims, though these spiders will not bite unless provoked.
With speeds clocked at 1.73 ft/s (0.53 m/s) (1.18 mph), the giant house spider held the Guinness Book of World Records for top spider speed until 1987 when it was displaced by sun spiders (solifugids) although the latter are not true spiders as they belong to a different order.
Relationship with Eratigena agrestis
A population of Giant house spiders is popularly thought to be a deterrent to the establishment of Eratigena agrestis, known in North America as the "hobo spider", and considered by some to be more likely to bite humans. Giant house spiders may compete with hobo spiders for the same resources. Hobo spiders grow no more than a body size of 15 millimetres (0.59 in) long whereas the larger female giant house spider can have a body size of 18 millimetres (0.71 in), but has proportionately much longer legs.
This species was referred to as Tegenaria gigantea until 1995, when researchers concluded that this name was a synonym of T. duellica (published in 1875), making the latter the oldest available name at that time. This species was then moved into a newly created segregrate genus named Eratigena (an anagram of Tegenaria) in 2013, along with several closely related species, and duellica, gigantea and other names were all synonymized under an even older species name, atrica.
In popular culture
Humorist David Sedaris has written about his relationship with E. atrica. His essay "April & Paris"  documents his growing affection towards and domestic association with giant house spiders, particularly one named April. The essay can be found in the collection When You Are Engulfed in Flames.
- Bolzern; Burckhardt, & Hänggi (2013). "Phylogeny and taxonomy of European funnel-web spiders of the Tegenaria-Malthonica complex (Araneae: Agelenidae) based upon morphological and molecular data.". Zoological Journal of the Linnean Society 168: 723–848. doi:10.1111/zoj.12040.
- Checklist of Danish Spiders (Araneae). Version 26-10-2011 (list)
- Platnick 2008
- Pourié & Trabalon 1999
- "Giant House Spider (Tegenaria gigantea)". Woodland Park Zoo. Retrieved 20 August 2013.
- "Species Tegenaria agrestis - Hobo Spider". BugGuide. Iowa State University. Retrieved 20 August 2013.
- "Species Tegenaria gigantea - Giant House Spider". BugGuide. Iowa State University. Retrieved 20 August 2013.
- "April & Paris". The New Yorker. Retrieved 14 September 2014.
- Pourié, Grégory & Trabalon, Marie (1999): Relationships Among Food and Contact Signals in Experimental Group-Living Young of Tegenaria atrica. Archives of Insect Biochemistry and Physiology 42': 188-197.
- Platnick, Norman I. (2008): The world spider catalog, version 8.5. American Museum of Natural History.
- Prouvost, O.; Trabalon, M.; Papke, M. & Schulz, S. (1999): Contact sex signals on web and cuticle of Tegenaria atrica (Araneae, Agelenidae). Arch. Insect Biochem. Physiol. 40: 194-202.
- Pourié, Grégory; Ibarra, Fernando; Francke, Wittko & Trabalon, Marie (2005): Fatty acids mediate aggressive behavior in the spider Tegenaria atrica. Chemoecology 15(3): 161-166. doi:10.1007/s00049-005-0308-6
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