''Amaurobius fenestralis'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...

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 collected in pitfall traps. Unlidded burrows are sometimes quite obvious in crusty, ...

. It is one of at least two common spiders found in houses known as lace-webbed spider, the other being '' Amaurobius similis''. The specific name ''similis'' is based on its similarity to ''A. fenestralis''. Both are often found near windows, hence the specific name of ''A. fenestralis''. The two species are difficult to distinguish: ''A. fenestralis'' tends to be smaller and lighter in colouration when an adult. Both species have V-shaped markings on their abdomens, with ''A. fenestralis'' usually having two or three, and ''A. similis'' four. Examination of the genitalia may be needed for precise identification. This spider has been seen preying on another spider, '' Steatoda nobilis'' in areas around the UK.

References

Amaurobiidae Spiders described in 1768 Taxa named by Hans Strøm {{Amaurobiidae-stub