There's a fly on my nose!

By Mike Ackland
Honorary Associate of the HEC

In September 2011, John Carr of Massachusetts, USA, posted photographs of an anthomyiid fly on the website diptera.info. This site has thousands of photos of flies, sent in by both diptera enthusiasts who are keen photographers, and experts who offer advice and possible identification.

I recognised the anthomyiid as a species of Eutrichota, which has over 50 species in the Nearctic Region. Positive identification to species however generally requires examination of a specimen under a microscope. John, who is a very good photographer and naturalist, later added to his posting some very clear close-ups of various parts of a male specimen he had caught, and offered to send the specimen to me. This proved to be Eutrichota affinis (Stein), a species widespread in America and which is associated with the groundhog Marmota monax L. and may be found in and around their burrows. The larvae are considered to be facultative commensals probably feeding in excrement and debris in the burrows.

A few other species of Eutrichota in North America have been associated with mammals including ground squirrels, Spermophilus tridecemlineatus (Mitchell), chipmunks, Tamias striatus (L.) and various species of gophers (Geomys spp.).

In Europe other species of Eutrichota have been found around the burrows of the Alpine Marmot Marmota marmota L. There are seven species of Eutrichota in Britain, though no life histories are known. See Pont & Ackland, 1995 for more details of the flies found in the Alps (full reference below). I first met Adrian Pont (another Hope Department Honorary Associate) in the mid 1950's in Leigh Woods near Bristol, where we were both collecting insects. So we have both been studying flies for over 50 years.

Recently John Carr sent me two photographs of specimens of Eutrichota affinis on the head and nose of a groundhog. These were taken in Connecticut on 30th May 2009. The groundhog family was living in a culvert, and John reports that they later ate part of his sister's garden!
My thanks to John for permission to use these excellent photos.

There's a fly on my nose!

Females of Eutrichota affinis (Stein)(Diptera: Anthomyiidae) on the head of the groundhog Marmota monax L.

Reference
Pont, A.C. & Ackland, D.M. (1995). Fanniidae, Muscidae and Anthomyiidae associated with Burrows of the Alpine Marmot Marmota marmota Linnaeus in the upper Ötz Valley (Tyrol, Austria). Insecta, Diptera. Berichte des naturwissenschaftlich-medizinischen Vereins in Innsbruck, 82: 319-324.

A pdf version of the paper is avaliable HERE.