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Platnick (2013) lists 528 species in the spider family Dysderidae (woodlouse spiders). Dysderids are native to the western Palearctic, with most species being circum-Mediterranean, many of them with narrow distributions (Cook 1965a,b; Ubick 2005). Just one of these species, Dysdera crocata, is found in North America north of Mexico (and it is not native; this synanthropic species has been spread widely around the world) (Ubick 2005; Bradley 2013).
Dysderids have six eyes, two in front and four behind, with the posterior row slightly procurved (i.e., the lateral eyes are anterior to the median eyes). There are two pairs of conspicuous spiracles under the abdomen. Dysderids have huge chelicerae and long fangs, giving them a fearsome appearance, but none of the scattered reports of humans being bitten by dysderids have been medically serious. These bites have sometimes resulted from the spider building its retreat in the fingers of a glove. (Bradley 2013)
Dysderids are widely believed to feed mainly on terrestrial isopods (woodlice, pillbugs). Although it is unclear how specialized dysderids are in nature (they will take a range of prey in captivity), some dysderid species are known to feed on isopods in the wild and their modified chelicerae and feeding behavior appear clearly to indicate at least some degree of specialization for capturing these prey and biting through their hard calcareous exoskeletons (Cooke 1965a,b; Pollard et al. 1995; Řezáč and Pekár 2007 and references therein; Řezáč et al. 2008).
Dysderids are nocturnal wandering hunters. They are ground dwellers, often found under rocks and logs in both grasslands and forests. Cooke (1965a,b) studied the life history of two British Dysdera species, D. crocata and D. erythrina. These spiders build retreats for molting and depositing eggs, which are loosely bound with silk and guarded by the female within a thick cocoon in which she seals herself. In captivity, these spiders reach sexual maturity in around 18 months and then live for an additional two to three years. In the Nearctic region, the introduced Dysdera crocata is found mainly in urban areas and disturbed habitats. (Cooke 1965a; Ubick 2005)