This is a small spider family of which only three species of the genus Segestria are found in Britain, only one of them widely distributed. They are elongated spiders, with only six eyes and the first three pairs of legs facing forward. They have a characteristic dark abdominal pattern, reminiscent of an adder's. They live in silk tubes in cracks in logs, walls, under stones and cliff faces. The tube opening is surrounded by at least six radial threads extending quite a way away, which act as signal threads to the spider sitting inside the funnel and are quite characteristic of the genus. The spider is active at night, when she comes out to her retreat's entrance, poised with her forward facing six legs touching the radial lines, awaiting passing insects.
Segestria florentina (top photo taken in Sheerness, Kent, courtesy of Robert Jaques) is a large spider that can reach 22 mm of body length. It is almost black with iridescent green chelicers. It lives near sea ports and it is thought to have been introduced from at least the 19th century with produce from the Mediterranean, from where it is native.
The female makes her egg sac inside her retreat and remains with her spiderlings until they disperse. Matriphagy, where the mother dies and the spiderlings eat her, has also been reported.