Lace web spider - Amaurobius species
Overall size: 20mm
Other names: Funnel weavers
Season: all year round. Usually found outdoors on walls, fencing and clutter around the garden, but most common in homes in autumn when males leave their webs to search for female spiders. Also common after heavy rain when they become flooded out of their own homes.
A medium-sized spider, usually brown and frequently having yellowish markings on the abdomen. Three related species live in Britain, living in tubular retreats within holes in walls, bark, etc. Their web is made of silk with a woolly texture due to extremely fine and sticky fibres, which gives them the name lace-weavers.
Adults are 5 to 15 mm long. Males are smaller than females but with longer legs. Amaurobius ferox is the largest on average, and the darkest. The other two are hard to tell apart, but if in house or garden it’s probably an A. similis, while if in woodland it’s more likely an A. fenestralis.
They superficially resemble false widow spiders (Steatoda sp.) and people often worry about them, but they are harmless.
Window spider (Amaurobius fenestralis)
Amaurobius fenestralis by Danny Steaven licensed under CC BY 1.0 via Wikimedia Commons
The window spider is found under tree bark, fallen logs, under stones, on plants with stiff, dense foliage, and in crevices in masonry, often around windows and sills, hence its name.
Lace-weaver spider (Amaurobius similis)
Amaurobius similis by David Featherston under CC BY-SA 2.0 via Wikimedia Commons / Cropped from original
The lace-weaver spider is the most common in gardens and around houses; in holes in walls, fences, window frames. Away from houses it is found in similar situations to A. fenestralis.
Black lace-weaver spider (Amaurobius ferox)
Amaurobius ferox by Danny Steaven licensed under CC BY 1.0, via Wikimedia Commons
The black lace-weaver spider is found in similar locations to A. similis, but more often under stones, hedgerows and logs.
All three species are occasionally found wandering in buildings, cellars and outhouses.
Life cycle
Females live for two years, while males only a few months. In late summer and autumn males wander in search of females. They strum silk threads in females’ webs to advertise their presence. The eggs are laid in a sac within the retreat in the summer of the following year. Females frequently die and are eaten by spiderlings before they disperse.
The web
The web is a tangled mesh of threads surrounding a circular retreat leading into a crevice, usually on a vertical surface. When fresh, it has a lace-like appearance and a bluish colour, and it is very sticky. The web is spun by night, but the spiders are ready to respond to any insect stuck in it at any time of day.
Get help identifying your spiders
You can email a photo to the Musuem's Identification and Advisory Service: bug@nhm.ac.uk
Please tell us as much about your specimen as possible, including a detailed description, where and when you saw it, and its approximate size.
Spiders in your home
Back to the Spiders in Your Home guide