Amaurobius fenestralis

This is a dark brown spider with a pale oval ring marking on its abdomen which has a dark 'cardiac' mark in its centre. It often has orange/brown chevrons below this cardiac mark. It is very similar to A. similis and the two cannot reliably be distinguished by eye. If in a garden or associated with houses then it is more likely A. similis , however if in woodland it is more likely to be A. fenestralis . Requires examination at high magnification in good lighting, typically examination of the genitalia. Requires examination at high magnification in good lighting, typically examination of the genitalia. Found under bark and stones, in crevices in masonry, often around windows and sills, hence its name. Predatory on many other invertebrates, including other spiders. Its web is characteristically very pale blue-grey or white, and the strands are 'fluffed' by the spider to tangle the feet of its insect prey. The web usually forms an open funnel leading to the spider's retreat in the deepest part of the crevice. The spider can be attracted from its lair by holding a sounding tuning fork against its web, presumably resembling the sound of a trapped insect. 5,115 British records for this species to 2015.