The spider family Filistatidae (crevice weavers) includes 115 described species (Platnick 2013). Seven of these species occur in North America north of Mexico, including five large spiders in the genus Kukulcania (the other two are small spiders, <5 mm long) (Bradley 2013).
The common name "crevice weaver" refers to the retreat these spiders build in a crack or similar space, usually among rocks or dead wood. The spider builds a silken tube in this space then extends a circular band of hackle-banded silk (i.e., silk from the cribellum) in a circular pattern around the entrance. From this circular area the spider spins a series of long trip lines, yielding a distinctive web. Crevice weavers can often be found in and around buildings. (Bradley 2013).
The synanthropic Southern House Spider (Kukulcania hibernalis) is found in the southeastern United States (Bradley 2013), but is also widespread in South America (Brescovit and Santos 2013). It is among the most common spiders within its range in the eastern United States (Howell and Jenkins 2004). The eight eyes are tightly grouped on a central mound (Bradley 2013). This spider exhibits conspicuous sexual dimorphism. The female is dusky gray or black with a velvety covering of hairs. The legs have velvet hairs and many short spines. The male is tan with long legs and palps. These palps are often held in a folded position position, extending directly in front of the chelicerae. Markings on the male's carapace (the upper part of the cephalothorax) often result in these spiders being misidentified as Brown Recluse Spiders (Loxosceles reclusa), although Brown Recluses can be easily distinguished from Southern House Spiders by the fact that they have six eyes rather than eight eyes (Howell and Jenkins 2004; Gaddy 2009). Although the female Southern House Spider stays around her web crevice, the male roams and hunts like a wolf spider or fishing spider (Gaddy 2009).
Crevice weaver spiders (Filistatidae) comprise cribellate spiders with features that have been regarded as "primitive" for araneomorph spiders. They are weavers of funnel or tube webs. The family contains 18 genera and more than 120 described species worldwide.
One of the most abundant members of this family in the Americas is the southern house spider (Kukulcania hibernalis). Named after the fierce Meso-American god Kukulkan, the females are large (up to nearly 20 mm) dark-colored spiders and males are light brown, smaller (about 10 mm), but more long-legged and with palps that are held together in front of their carapaces like the horn of a unicorn. The males also have a darker streak on the center of the dorsal carapace that causes them to be often mistaken for brown recluse spiders. The tiny members of the genus Filistatinella are like miniature versions of Kukulcania. The nominate genus Filistata is Afro-Eurasian in distribution. In many older books the species from the Americas now placed in the genus Kukulcania are placed in Filistata.
A striking visual characteristic of the family, beside dimorphism, is the unusual upward bend encountered near the femur of the first pair of legs. While resembling hydraulic muscle mechanisms akin to arthropods, this modification actually allows the spider to retain the prey directly from the crevice it occupies. Also, if the larger prey ever tries to pull it from the crevice, the spider can use these legs to "grab" to the side walls and hence make it difficult. Many Kukulcania species also use them to dig holes in the soft ground at a 25- to 30-degree angle.
The family Filistatidae was created in 1867 by Anton Ausserer.[1] It was based on the species he called Filistata bicolor (now Filistata insidiatrix), a Mediterranean species also found in southern Austria.[2][3]
On the basis of the features of the male and female genitalia, the family was placed in the Haplogynae, usually as the sister taxon of the remaining members of the group.[4] However, unlike the other haplogynes, Filistatidae are cribellate and do not show a decrease in the number of segments of the anterior lateral spinnerets.[5] They have other features which have been regarded as "primitive": an M-shaped intestine, only leg IV moving while combing silk, and posterior book lung leaves being present in early juveniles.[6] A 2013 study based on molecular evidence placed the family as sister to a clade consisting of Hypochilidae and the remaining haplogynes.[7] The precise phylogenetic position of the family was described in 2014 as "one of the most enigmatic problems in spider phylogeny".[5]
A 2015 study, based on genomic data, places Filistatidae with Hypochilidae in a clade outside most of the families previously placed in Haplogynae:[8]
AraneomorphaeHypochilidae
Filistatidae
most other "traditional" haplogynes
Entelegynae
This placement suggests that features that were thought to be "primitive" to araneomorph spiders as a whole (such as an M-shaped midgut) could actually be novel derived features (synapomorphies) of the Hypochilidae-Filistatidae clade.[8]
As of April 2019, the World Spider Catalog accepts the following genera:[9]
Kukulcania hibernalis male
Crevice weaver spiders (Filistatidae) comprise cribellate spiders with features that have been regarded as "primitive" for araneomorph spiders. They are weavers of funnel or tube webs. The family contains 18 genera and more than 120 described species worldwide.
One of the most abundant members of this family in the Americas is the southern house spider (Kukulcania hibernalis). Named after the fierce Meso-American god Kukulkan, the females are large (up to nearly 20 mm) dark-colored spiders and males are light brown, smaller (about 10 mm), but more long-legged and with palps that are held together in front of their carapaces like the horn of a unicorn. The males also have a darker streak on the center of the dorsal carapace that causes them to be often mistaken for brown recluse spiders. The tiny members of the genus Filistatinella are like miniature versions of Kukulcania. The nominate genus Filistata is Afro-Eurasian in distribution. In many older books the species from the Americas now placed in the genus Kukulcania are placed in Filistata.
A striking visual characteristic of the family, beside dimorphism, is the unusual upward bend encountered near the femur of the first pair of legs. While resembling hydraulic muscle mechanisms akin to arthropods, this modification actually allows the spider to retain the prey directly from the crevice it occupies. Also, if the larger prey ever tries to pull it from the crevice, the spider can use these legs to "grab" to the side walls and hence make it difficult. Many Kukulcania species also use them to dig holes in the soft ground at a 25- to 30-degree angle.
