Tube Web Spider

The tube web spider belongs to the family Segestriidae, a group of elongated, fast-moving spiders best known for the distinctive silken retreat that gives them their common name. Rather than spinning a flat, sticky orb to catch prey, a tube web spider builds a tapering silk tunnel deep in a wall crack, beneath loose bark, or under a stone, with a scatter of non-sticky trip threads radiating outward from the entrance like the spokes of a wheel.

The best-known species, Segestria florentina, is native to southern Europe but has spread through human commerce to parts of North America and elsewhere, where it often colonizes old stone or brick walls. Its cylindrical body and forward-projecting fangs give it a streamlined, almost centipede-like silhouette that sets it apart from the average web-building spider.

Because the spider spends nearly all its life hidden inside its tube, most sightings happen at night when the animal's front legs can be seen resting just inside the tunnel mouth, poised to detect vibrations transmitted along the trip lines.

• Elongated, parallel-sided body rather than a rounded abdomen
• Eight eyes clustered tightly together at the front of the head
• Long, forward-pointing chelicerae (fangs); in Segestria florentina these can show a metallic green or purple iridescence
• Legs held forward in pairs, useful for gripping tube walls and racing outward along trip lines
• Silk retreat is a tapering tube with loose trip threads fanning out from the entrance, distinct from a woven sheet or orb
• Lookalikes include other tube-dwelling spiders and some funnel-web weavers, but the tight eye cluster and tube-plus-radiating-threads combination are diagnostic

Tube web spiders favor vertical or sheltered surfaces with narrow crevices: old stone and brick walls, tree bark, fence posts, and rock outcrops. They are most active from late spring through autumn in temperate climates, retreating deeper into their tunnels during cold weather. The group has a wide distribution across Europe, parts of Asia, and, through accidental introduction, isolated urban populations in North America.

These spiders are ambush predators. They remain hidden inside their silk tube with their front legs resting on the trip lines that radiate from the entrance; when a passing insect brushes one of these threads, the spider senses the vibration and darts out to grab it before retreating back into the tunnel to feed. Diet consists mainly of crawling and flying insects such as beetles, flies, and woodlice that wander near the tube entrance. In the wider ecosystem they help regulate populations of small arthropods living in and around masonry and bark crevices.

Females lay eggs in a silken sac tucked inside or near the tube retreat and often guard the sac until spiderlings emerge. Young spiders disperse to find their own crevices, where each spins a miniature tube and begins hunting almost immediately, growing through a series of molts over one to two years. Adults can survive multiple seasons, sheltering in their tubes through winter in temperate regions before mating in the following warm season.