Eratigena atrica is one of the three spider species (along with E.duellica and E.saeva) commonly called giant house spiders. They are large synanthropic spiders native to Europe and introduced to North America. Their bites are not considered dangerous to humans or pets. Giant house spiders have sometimes been considered a single species, collectively called E.atrica, but have been accepted as separate species since 2018 due to small but consistent differences in morphology.
Description
Nomenclature The genetic study which moved giant house spiders into the new genus Eratigena collapsed several previously defined species into E.atrica broad sense. A 2018 study of genetics and morphology of European giant house spiders found three well-separated morphological groups, leading to restoration of the three separate species. While morphologically distinct, they have little genetic differentiation, suggesting that the species are young.
The genus name Eratigena is an anagram of Tegenaria, the genus from which it was split. The species name atrica means "from the atrium" and may refer to the greenhouse in which the first described specimen was found, or its general tendency to live in houses.
Distribution
Eratigena atrica is native to Europe. The E.atrica specimens used to delineate the three species came from Britain, France, Germany, Belgium, the Netherlands, Switzerland, Austria, Sweden and Finland. It is also found as an invasive species in North America, with populations in British Columbia and extending into Montana, and also in Quebec, Newfoundland, and Nova Scotia. (The giant house spiders found in the US Pacific Northwest are generally E.duellica.)
Genomics
Whole-genome sequencing of a male E. atrica found 22 pairs of chromosomes. There are two different X chromosomes, X1 and X2, but no Y chromosomes: males are X1 X2 and females are X1X1 X2X2. This is the most common and probably ancestral form of sex determination in spiders.
While E. saeva and E. duellica have been hybridized in captivity, there is no evidence that E. atrica can hybridize with the others. A survey of an area in England where all three species coexist failed to find any apparent hybrids in the wild.
Habitat and behavior
Giant house spiders, including E. atrica, often live in buildings, favoring hidden locations such as behind crates, around windows, or under furniture. They make flat, irregular webs with a funnel at one end. Despite their large size they are generally inconspicuous, except for males in mating season (late summer and fall) which wander while searching for females. Their bites are not generally considered dangerous to humans or pets.
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