A piece of lint

December 17th, 2015

A piece of lint

On  July 4th, 2009, I was busy doing Saturday chores at home in Ithaca. We’d been going inside and out, when I noticed a fuzzy black piece of lint on a white linoleum floor. Our dog is black and furry so he was my first hunch as the source. But, this lint looked just a little bit odd, so I found my hand lens to take a look. As an undergraduate at the University of California, Berkeley, I’d done invertebrate surveys and worked as a teaching assistant for a field entomology course taught by Dr. Evert Schlinger, an acrocerid expert. To my surprise, the ‘lint’ turned out to be a member of the Acroceridae, a small family of peculiar-looking flies uncommonly collected in the Northeastern United States .

Acrocerids have a large humpback and a small head, hence the common name small-headed flies. To show how uncommon they are, the Cornell Insect Collection contains approximately 13,000 drawers of insects and only one drawer houses the acrocerids. This species keyed out as Pterodontia westwoodi, with no other specimens of this species and only one other species of the genus in Cornell’s collection. Pterodontia flies have a tooth on the front edge of the forewing, which explains the genus name Ptero-dontia; the flies are pretty hairy and the short wings and thick body suggest that they aren’t strong fliers. P. westwoodi was first described in 1848 from Georgia and, since then, it’s only been reported from 4 other locations in the eastern US (Long Island, Woods Hole, Beltsville and now Ithaca). The larvae of acrocerids are endoparasitoids of spiders. Other species of Pterodontia have been reported as depositing eggs while flying by flicking them onto vertical surfaces. The first instars are planidia, i.e. active legless larvae that locate hosts. We don’t know why this species is so rare; perhaps it is common but just not located where and when entomologists are looking for specimens. So, be on the lookout and you too could come up with rare insect specimens when you should instead be doing Saturday chores.

Ann Hajek, with insect identification by Jim Liebherr

(This piece previously published in the 2010 Cornell Department of Entomology Newsletter)

Ann Hajek--Associate Curator