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The mygalomorph spider family Dipluridae (funnel-web spiders) includes 179 described species (Platnick 2013); most species are tropical, but five occur in North America north of Mexico (Coyle 2005; Bradley 2013). The family is perhaps best known for the dangerously venomous Sydney Funnel-web Spider (Atrax robustus) of Australia (Bradley 2013).
The two genera in the United States are found in the southwestern United States (Euagrus) and in the southern Appalachians and Pacific Northwest (Microhexura). Euagrus spiders are among the most common mygalomorphs in Mexico and Central America, with three species occurring in North America north of Mexico. Microhexura includes just two species (see below). Spiders in both genera build ground webs composed of flattened, often branching, tubular retreat passages connected to small, irregular sheets. These webs are often hidden under objects or in soft, porous organic substrates. Euagrus prefers riparian, woodland, and forest habitats. Euagrus webs are typically found beneath rocks, but inconspicuous irregular funnels and sheets often extend into surrounding leaf litter. Microhexura montivaga, a federally listed endangered species in the United States, is restricted to remnant patches of fir forest on a few high peaks in the southern Appalachian Mountains, where it lives almost exclusively under moss mats on rock outcrops. The other Microhexura species, M. idahoana, is widespread in Pacific Northwest conifer forests, where its webs are often common in or under rotting logs and other organic debris. (Coyle 2005) More information on the natural history of Microhexura can be found in Coyle (1981, 1985). Information on Euagrus can be found in Coyle (1988).
Diplurids have only four spinnerets, having lost the anterior pair. The median spinnerets have one short segment. The posterior spinnerets are long, widely spaced, and conspicuous. (Bradley 2013)