A Tiny Little Scavenger

Just a quick note tonight, about this little guy:

Black Scavenger Fly, family Sepsidae, Lyons Woods FP, Lake Co, IL 4/17/2014

This is a male Black Scavenger Fly, in the family Sepsidae. According to Arnett, there are 34 species north of Mexico, (1) and many of them look similar, so I'll probably never know which one.

These guys have some rather unsavory habits, by our standards: their larvae feed in animal droppings. The adults tend to hang out nearby, and mating takes place almost exclusively near dung. This happens soon after the material is deposited, (2) and often involves some very species-specific structures on both male and female. (This sort of thing isn't unusual in many insects.) Such specialization most likely happens through various forms of sexual selection, and since these guys are easy to attract, they've been used to test a number of hypotheses about the forms that sexual selection can take. (3,4)

Yesterday I didn't even know this family existed, and today, I find out that its a commonly researched group of critters! It's no wonder biologists specialize -- a whole planet full of critters is simply too much for any one person to truly comprehend.

(1) Arnett, R. (2000). American insects: a handbook of the insects of America north of Mexico. CRC Press, Boca Raton.

(2) Parker, G. A. (1972). Reproductive behaviour of Sepsis cynipsea (L.)(Diptera: Sepsidae). I. A preliminary analysis of the reproductive strategy and its associated behaviour patterns. Behaviour, 172-206.

(3) Puniamoorthy, N., Ismail, M. R. B., Tan, D. S. H., & Meier, R. (2009). From kissing to belly stridulation: comparative analysis reveals surprising diversity, rapid evolution, and much homoplasy in the mating behaviour of 27 species of sepsid flies (Diptera: Sepsidae). Journal of evolutionary biology, 22(11), 2146-2156.

(4) Eberhard, W. G. (2005). Sexual morphology of male Sepsis cynipsea (Diptera: Sepsidae): lack of support for lock-and-key and sexually antagonistic morphological coevolution hypotheses. The Canadian Entomologist, 137(05), 551-565.