Two new spider families discovered in Washington state

When I tried to take it through Roth’s family key to North American spiders, it went precisely nowhere. “Well,” said I, “this spider is now officially upgraded from ‘curious’ to ‘bizarre.'” Finally the excellent keys on the Spiders of Europe website led to the answer: the appearance of only two spinnerets (most spiders have six) made this spider a member of Zodariidae, a family not known from Washington and never before seen by me; the species is Zodarion rubidum.

Zodarion rubidum is widespread in southern and central Europe, and was found introduced in a Pennsylvania quarry in 1967. By 1999 it had spread to Colorado, and now it’s here in Washington state! (P.S., this spider has no common name at all.) Excited by her new find (an adult female), Laurel re-checked the May 9 sample, and it included an adult male Zodarion! What’s more, she also had juvenile Zodarion from two sites in Pierce County. So it’s definitely part of the Washington fauna now.

This 4-millimeter-long spider has some interesting habits. It is an obligate myrmecophage: in other words, it will not take any prey but ants (which most spiders won’t eat at all). When at rest, it lives in a little igloo-shaped structure make of tiny pebbles and debris fastened together with silk. It favors the habitat of loose rock slopes at the sides of railroad tracks, and some writers suspect the species spreads to new habitats along railroads. The Gold Bar site is only 178 meters from the BNSF Railroad tracks.

Family Desidae

Meanwhile, in early June, volunteer Ben Diehl was weeding a garden plot in front of the apartment building where he lives in Burlington, Washington. He had a vial handy to collect any spiders that turned up among the weeds. Just before departing the Burke for his new full-time job, he handed this vial to me, and I finally looked through it at the end of July.

One of the seven spider specimens was very unfamiliar! It seemed to be in the family Amaurobiidae, but didn’t match any known species or even genus. Finally I went back to the good old Spiders of Europe website, only to find I had the first Washington specimen of a species with the tongue-twisting name Badumna longinqua. It is currently placed in the family Desidae, not previously known from Washington.

Article Source: Burke Museum