Winter Crane Flies

2013 October 23

In November of 2012, we had a few nights that were above freezing, so I left the porch light on through the nights of November 4, 18, and 22. And each time, among the insects that came to the light were these small crane flies.

November 4:

November 18:

November 22:

All of these look pretty much identical to my eye, so I suspect they are all the same species.

They are about 50% longer than the average mosquito, and appear to be Winter Crane Flies in the genus Trichocera. These are very cold-tolerant flies, and I sometime see them on our windows during brief thaws all through the winter. Even in January and February.

Most of the winter crane flies we get look like they are all from one species, but we sometimes get these, too, which have more rounded, pear-shaped wings (this one is also from the 18th):

There are apparently 25 species in the Trichocera genus, and BugGuide makes no attempt to differentiate them, because you need to spend some serious time looking at leg structure and wing vein patterns to tell them apart. They do have a link to an ID key, which is this paper (pdf), but the first few key items look like they need a microscope, and I don’t think my pictures show quite enough detail for them. Darn.

Anyway, the larvae spend the late spring, summer, and early fall in moist areas where there is a lot of rotting material. Once it gets cold enough that most of the things that prey on flying insects have either migrated, hibernated, or died for the winter, the adult winter crane flies emerge to mate and lay eggs. They do need it to be above freezing before they will fly, but not by much. I expect that their blood is basically antifreeze so that they don’t die when it actually does freeze. I can’t imagine that the adults eat much of anything, because where would they get it?

2 Responses
  1. Andrius permalink
    October 23, 2013

    Hi, these are really Winter Crane Flies, genus Trichocera. Most of them are rather hard to identify to species, especially females, and microscope is needed in many cases as well. Nevertheless, the 4th and 6th images show Trichocera annulata – one of the common species that is spread in many countries with colder climates around the world. As H.D.Pratt puts it in the key mentioned “abdomen distinctly annulate, tergites obscurely yellowish with posterior margins brownish” 🙂

  2. October 23, 2013

    Some bugs are glorious. Some bugs are meh. Despite your awesome photography and engaging prose, crane flies are doomed to the meh category.

    It’s like being Roseanne Barr’s make up artist. You’ve got nothing to work with here.

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