Eratigena atrica
| Giant house spider | |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Class: | Arachnida |
| Order: | Araneae |
| Infraorder: | Araneomorphae |
| Family: | Agelenidae |
| Genus: | Eratigena |
| Species: | E. atrica |
| Binomial name | |
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Eratigena atrica (C. L. Koch, 1843) |
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| Synonyms | |
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The giant house spider, now with the scientific name Eratigena atrica, is one of the biggest spiders of Central and Northern Europe. It was previously placed in the genus Tegenaria, where in addition to Tegenaria atrica, it was also documented as Tegenaria duellica, Tegenaria gigantea and Tegenaria saeva, among others, all thought to be different species. It is now a member of the newly described genus Eratigena. The bite of this species does not pose a threat to humans or pets, and it 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, Tegenaria domestica; it has earthy tones of brown and muddy red or yellow. They also have conspicuously hairy legs, palps and abdomen. The female body size can reach 18.5 millimetres (0.73 in) in length (despite its English name, the species is 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, E. atrica can probably only distinguish light and dark.
The first description of a spider now assigned to this species was by Carl Ludwig Koch in 1843, under the name Tegenaria atrica. Other supposedly different species were described later, including Tegenaria saeva by John Blackwall in 1844, Tegenaria duellica by Eugène Simon in 1875 and Tegenaria gigantea by Ralph Vary Chamberlin and Wilton Ivie in 1935. T. gigantea was synonymized with T. duellica in 1978. The three remaining taxa have been regarded as distinct species, particularly in Britain. Thus Roberts (1995) provides distinguishing characters for T. atrica, T. duellica and T. saeva, as does Oxford (2008) for T. duellica (as T. gigantea) and T. saeva. Others consider these three as part of a single morphologically variable species, for which the oldest name, and hence the senior synonym, is T. atrica.
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