In much of Delaware County, secretive spiders spin tube-like webs along the bases of trees. Atypus snetsingeri (like a lot of bugs, it doesn’t have a common name) waits in a burrow below for an unsuspecting insect to brush against the web. Using enormous chelicerae (fangs) it stabs through the web, paralyzing its prey, and then drags it inside to drink its liquified insides.
A. snetsingeri has a lot of fans for a reclusive and somewhat intimidating spider. It has been the subject of nature walks at Tyler Arboretum, where it is quite common, and it inspired a citizen science effort to map its range.
For decades the spider puzzled arachnophiles and scientists, since it didn’t have any close relatives outside of Asia. A new study looking into the genetics of the apparently enigmatic spider reveals why: the A. snetsingeri that calls the Philly area home is identical to a species from East Asia, Atypus karschi. In other words, the local spiders were transplants all along.
It is impossible to say exactly how the Asian spiders made it to Delaware County, but, like a lot of small critters, it probably hitched a ride in the soil around the roots of imported plants, which might explain its abundance at Tyler Arboretum.