Segestria

Distinguished from other spiders by the combination of six eyes in three pairs (rather than eight) and the elongated, cylindrical body form. The anteriorly directed legs and tubular retreat-building behavior are additional diagnostic features. Differs from the related genus Ariadna (also Segestriidae) in eye arrangement details and geographic distribution. The eye pattern alone separates Segestria from all other spider families except Dysderidae, which have a different body shape and six eyes in a different arrangement.

Body elongated and cylindrical, with a somewhat flattened carapace. Six eyes arranged in a semicircle of three pairs anteriorly, rather than the eight eyes typical of most spiders. Chelicerae large and project forward. Legs long and slender, with the first three pairs directed forward and the fourth pair backward. Coloration generally dark brown to black, often with faint patterning. Spinnerets reduced, with only the posterior pair functional; cribellum absent.

Found in rocky habitats, walls, tree bark, and other situations providing cracks and crevices suitable for tubular retreat construction. Often occurs in human-modified environments such as stone walls, old buildings, and bridges. Requires sheltered microhabitats that allow construction of silk-lined tunnels.

Primarily Palearctic, with the majority of species in Europe and Asia. Disjunct populations in North America (introduced or native), North Africa (two species), Madagascar (S. madagascarensis), and New Zealand (one species).

Active nocturnal hunters that use silk triplines radiating from the retreat entrance to detect prey. Prey includes various insects and other small arthropods that blunder into the triplines; the spider rushes out to capture them.

Reproduction involves egg sacs placed within the female's retreat. Development includes egg, spiderling, and adult stages. Spiderlings likely disperse by ballooning or wandering, though specific details are poorly documented for most species.

Constructs tubular silk-lined retreats in crevices, with several silk triplines extending across the substrate to detect vibrations. Spends most of time inside the retreat, emerging rapidly when prey contacts a tripline. Non-aggressive toward humans; bites rare and not considered medically significant.

Predator of small arthropods in rocky and crevice habitats. May contribute to control of insect populations in urban and natural settings. Serves as prey for larger arthropods, birds, and other vertebrates.

Occasionally found in homes and buildings, particularly older structures with stone or brick walls. Not considered a pest species. Bites are rare and cause only minor local symptoms. Some species have been transported internationally via human commerce.

• AriadnaAlso in family Segestriidae with similar tubular retreat construction; differs in eye arrangement details and primarily tropical distribution
• DysderaAlso has six eyes, but eyes are arranged differently and body is more compact with enlarged chelicerae for preying on woodlice

• spider
• arachnid
• tubular retreat
• crevice-dwelling
• nocturnal hunter
• six eyes

• BugGuide
• Wikipedia
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life