''Amaurobius similis'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

in the family Amaurobiidae. It is one of at least two common spiders found in houses known as lace-webbed spiders. The specific name ''similis'' is based on its similarity to the species ''

Amaurobius fenestralis ''Amaurobius fenestralis'' is a species of spider in the family Amaurobiidae ''Amaurobiidae'' is a family of three-clawed cribellate or ecribellate spiders found in crevices and hollows or under stones where they build retreats, and are often c ...

''. Both are often found near windows, hence the specific name of ''A. fenestralis''.

Description

Mature males have a body length of 6–8 mm, females 9–12 mm. The carapace is dark reddish-brown in colour, with a darker head area. The top of the abdomen has a dark wedge shaped marking, edged with yellow towards the anterior. The legs are coloured as the carapace, and bear darker annulations. The species is very visually similar to ''A. fenestralis'' and, while ''A. similis'' tends to be larger and darker in colouration when mature, microscopic examination of the genitalia is necessary for reliable identification of the two species.

Distribution and habitat

''Amaurobius similis'' has a

Holarctic The Holarctic realm is a biogeographic realm that comprises the majority of habitats found throughout the continents in the Northern Hemisphere. It corresponds to the floristic Boreal Kingdom. It includes both the Nearctic zoogeographical region ...

distribution, and is found throughout

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

and the

Caucasus The Caucasus () or Caucasia (), is a region between the Black Sea and the Caspian Sea, mainly comprising Armenia, Azerbaijan, Georgia, and parts of Southern Russia. The Caucasus Mountains, including the Greater Caucasus range, have historically ...

. It has also been introduced to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. The species is found primarily in or around buildings, where it spins a web in holes in walls, fences and window frames. It is also less commonly found under bark in more natural habitats, such as woods.

References

Amaurobiidae Holarctic spiders Spiders described in 1861 {{Amaurobiidae-stub