Wednesday, June 22, 2011

Deer Fly? Maybe.

This blog is called "What Do I Know?"  But I'm probably more interested in "How Do I Know?"  Since my camera does a decent job of taking macro shots, I've been able to take fairly close-up pictures of bugs.  But that leaves me with the problem of identifying them.  So, I bought Dominique M. Collet's Insects of south-central Alaska. Sometimes it gives me a pretty clear id, like for the birch shield bug. But other times it leaves me still uncertain, but it narrows down the possibilities and then I can start googling.

The book has 29 families of flies. (He includes mosquitoes and midges.
"The most distinguishing characteristic for these insects is a pair of well-developed forewings and hindwings (halteres) reduced to stubs.")
Most of us probably can distinguish 'flies' from 'mosquitoes', but now we have 27 more different specific families.  And then each family can be broken down - though he doesn't do that for most.  You can see, though, how the more you know, the more you realize how much you don't know.  And if you're honest with yourself, you'll realize that what you don't know dwarfs what you do know.  And this should lead to humility. 

Going through the pictures, I decided the deer fly seemed the most likely.  Especially this:
"These . . . flies have gold and green metallic eyes . . ."
So I googled deer fly (family Tabanidae).

Bugguide offers a lot more detail. [my comments in brackets below]
"Medium to large flies, females take blood, and some are pests. Typical characteristics:
  • stoutly built flies with large squamae (scales above the halteres, also called calypters);
    [It is stout.  I'm not positive about the squamae.  If you click the links to halteres it tells you
    "calypter noun - a small membranous flap at the base of the hind edge of the wing in some flies; it covers the halteres."
    but I can't tell from the pictures they provide and this one I took. There is a lump at about where the wing comes in.]
  • feet with 3 pads (as opposed to 2); [My picture doesn't show the foot pads]
  • 3rd antennal segment elongated, clearly made up of several fused parts; [???]
  • 3rd antennal segment with a prominent tooth at base in some groups [????]
  • wing veins R4 and R5 fork to form a large 'Y' across the wing tip." [Yes! you can see the Y pattern of the veins on the wing.  Look at the tip of the wing on the left.]

So, I'm not certain, but at this point I'm tentatively identifying this as a deer fly until I get more evidence one way or the other.


  1. Looks more like a horse fly species to me. We have both deer and horse flies and the horse flies have those lovely slicing mouth parts that are almost as big as their evil heads.

  2. Flies? Interesting hobby. I always hated Biology, especially flies and bugs. They disturb me a lot. However I can imagine, that on a professional level it is interesting to someone. Nowadays I am preparing to an university contest and for 3 days I made a lot calculations about budget deficit. It is boring to most of the people, but interesting to me.

  3. Anon, you may well be right - that's why I was tentative. I was taken in by the 'gold and green metallic eyes' description of the deer fly (but not of the horse fly.) They are both in the family Tabanidae.

    Ropi, I think anything can be interesting if one gets to know more about it and if they are presented in a way that you can relate to. Are you writing your report in Hungarian or English?

  4. Is it the same camera you had last year? Amazing focus!

  5. Tómas, I thought the focus was pretty good too, until I saw the pictures at


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