Waiter, there’s a fly on my fungus…

On my recent season-opening-birthday-bug-collecting-trip in Sam A. Baker State Park, Rich and I happened upon a large grape (Vitis sp.) vine hanging from a tree in the bottomland forests along Big Creek. Draped over a foot-long section of the lower vine was a weep area covered with a thick fungal growth, softly colored in pink and white and on which a large number of “fruit flies” had congregated.  Their small size provided a good opportunity to get some more field practice with my MP-E 65mm macro lens, an opportunity made all the more challenging by the angle of the vine and its closeness to the tree upon which it was climbing.  There were quite a number of the flies feeding and mating, but they were quite difficult to approach and photograph – annoyingly taking flight or moving to the other side of the vine no matter how deliberate my movements.  Every now and then I found a relatively more cooperative subject and was able to get in a shot or two before it, too, moved nervously to the other side.  I probably also missed a few good shots when I got distracted watching their feeding behavior through the lens at higher magnifications (2-3X).  It was fascinating watching as they scraped their labellum on the surface of the fungus – I’d never seen this behavior up so close and personal before.

Keith Bayless kindly identified these as belonging to the family Drosophilidae, possibly in one of the smaller genera of Drosophila sensu lato.  I suppose a more specific ID would require a good view of its chaeotaxy (the arrangement of the bristles).  Now… I’m about as pedantic as they come, but I must admit to difficulty in calling these by their more proper common names of pomace, vinegar, or wine flies rather than the more widely used but technically incorrect “fruit flies” (the latter term referring to species in the family Tephritidae and including such important agricultural pests as the Mediterranean fruit fly and olive fruit fly).  When I was a kid and we saw swarms of these things rising up from overripe bananas, they were fruit flies.  When I got older and reared Drosophila in high school biology, they were fruit flies.  Not until I took Systematic Entomology as a college junior did I learn that fruit flies are something else and these are actually pomace flies, but by then it was too late.  These are fruit flies! (And later in the day we found some “big black ants“!)

Photo Details: Canon 50D (ISO 100, 1/250 sec, f/14), Canon MP-E 65mm macro lens (2-3x range), Canon MT-24EX flash (1/8 ratio) w/ Sto-Fen diffusers.  Typical post-processing (levels and unsharp mask).  Photo 1 slightly cropped.

Copyright © Ted C. MacRae

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