Segestriidae

Segestriidae can be distinguished from other spider families by the combination of six eyes arranged in a semicircle (vs. eight eyes in most spiders) and three pairs of legs directed forward (vs. two pairs in most spiders). These features are diagnostic at the family level. Within the family, genera can be distinguished by genitalic morphology, leg spination patterns, and other somatic characters. Ariadna, the largest genus, is characterized by particular palp structures in males and distinct genitalia in females. The genus Indoseges from India resembles Ariadna but differs in male first leg spines, apophysis shape and position, and female palp tarsi spination.

Segestriidae spiders have six eyes arranged in a semicircle, distinguishing them from the eight-eyed majority of spiders. The first three pairs of legs are directed forward, an adaptation for tube-dwelling life, compared to the two forward pairs typical of most spiders. The leg structure facilitates movement within silken tubes and burrows. Body form varies among genera, with Ariadna species showing considerable morphological diversity across their range.

Segestriidae are tube-dwelling spiders that construct silken tubes or burrows in various substrates. They inhabit diverse environments including soil, rock crevices, and human structures. In arid regions such as the Namib Desert, Ariadna species construct burrows in gravel plains and surround the entrance with stone rings. The family shows remarkable habitat flexibility, with one species (Ariadna phantasma) being halotolerant and inhabiting salt lakes in Western Australia, where it constructs burrows into the lake surface. Some species are found in human dwellings, constructing webs in window frames and eaves.

Global distribution on all continents except Antarctica. Greatest diversity occurs in tropical and subtropical regions. The Americas harbor significant diversity, particularly in Brazil, Chile, and Central America, with 31 nominal species recognized in the American continent. Australia contains at least 14 described species of Ariadna, with high diversity in South Australia and Victoria. India has documented Segestriidae from Odisha and other regions. The family extends into temperate regions, with records from southern and potentially mid-Atlantic United States. Namibian populations show strong genetic structuring correlated with environmental parameters.

Segestriidae are sit-and-wait predators that capture prey from their tube retreats. The specific diet composition has not been documented in the available sources.

Segestriidae are tube-dwelling spiders that spend their lives in silken tunnels or burrows, functioning as sit-and-wait predators. They construct and maintain tubular retreats from which they capture passing prey. In arid environments, Namibian Ariadna species surround their burrow entrances with stone rings, a distinctive behavioral trait. The developmental cycle from egg to adult has been documented in at least one species (Ariadna mollis), with parasitoid wasp development taking 24 days, though this reflects the parasitoid rather than the spider's own development. Females of some species may continue molting after reaching adulthood, a trait shared with mygalomorph spiders.

Segestriidae function as sit-and-wait predators in their respective ecosystems. In arid environments such as the Namib Desert, they contribute to invertebrate biodiversity in gravel plain habitats. Their specialized habitat requirements in some cases (e.g., salt lake endemism) make them potential indicators of ecosystem health and candidates for conservation attention. The family serves as host for parasitoid wasps in the genus Epipompilus (Pompilidae), with Ariadna mollis documented as host for Epipompilus excelsus in Brazil.

Some Segestriidae species occur in human dwellings, constructing webs on exterior window frames and under eaves, though they are not considered pests. They are not dangerously venomous to healthy humans. The family has been subject to taxonomic confusion with other spiders; for example, some Ariadna species have been mistaken for brown recluse spiders or filistatid crevice weavers due to similar web structures. Their tube-dwelling habits and distinctive morphology make them subjects of ecological and behavioral research, particularly in arid-adapted systems.

• Filistatidae (crevice weavers)Similar tube-like or funnel-like web structures issuing from holes; both families have been confused in field observations. Distinguished by eye number and arrangement: Segestriidae have six eyes in semicircle, Filistatidae have eight eyes. Filistatidae are cribellate spiders with calamistrum on fourth legs, a feature absent in Segestriidae.
• Agelenidae (funnel-web spiders)Construct funnel-shaped webs with retreat tubes that can resemble Segestriidae webs. Distinguished by eye arrangement and number: Agelenidae have eight eyes in two rows, Segestriidae have six eyes in semicircle. Agelenidae have two pairs of legs directed forward, Segestriidae have three.
• Brown recluse spiders (Sicariidae)Male Segestriidae have been mistaken for brown recluse spiders due to similar coloration and long legs. Distinguished by eye number: Segestriidae have six eyes in semicircle, brown recluse have six eyes in three pairs across front of carapace. Male Segestriidae have extremely long, elbowed pedipalps not seen in recluse spiders.

• six-eyed spiders
• tube-dwelling
• burrow-dwelling
• sit-and-wait predators
• cryptic species
• arid-adapted

• BugGuide
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Bug Eric: Spider Sunday: Crevice Weavers
• The taxonomy of the American Ariadna Audouin (Araneae: Synspermiata: Segestriidae)
• A ghost in the salt: A new species of halotolerant tube-web spider in the genus Ariadna (Araneae: Segestriidae)
• Description of a new genus and five new species of tube-dwelling spider family Segestriidae (Araneae: Synspermiata) from Odisha, India
• Do habitat features affect the composition of silk proteins by Namibian arid-adaptedAriadnaspiders (Araneae: Segestriidae)?
• The Tube-Web Spiders of the Genus Ariadna (Araneae: Segestriidae) from South Australia and Victoria
• How soil granulometry, temperature, and water predict genetic differentiation in Namibian spiders (Ariadna: Segestriidae) and explain their behavior
• First record of Epipompilus excelsus (Bradley, 1944) (Hymenoptera, Pompilidae) as a koinobiont ectoparasitoid of Ariadna mollis (Holmberg, 1876) (Araneae, Segestriidae)
• Figure 1 from: Villanueva-Bonilla GA, Brescovit AD, dos Santos EF, Vasconcellos-Neto J (2018) First record of Epipompilus excelsus (Bradley, 1944) (Hymenoptera, Pompilidae) as a koinobiont ectoparasitoid of Ariadna mollis (Holmberg, 1876) (Araneae, Segestriidae). Journal of Hymenoptera Research 66: 15-21. https://doi.org/10.3897/jhr.66.28915