Green Crane Fly

2023 July 2

It has been a while since I left the porch light on to draw in insects, so I did that on June 30, 2023. One of the insects that came in was this green crane fly. It is one of the crane flies in the Erioptera chlorophylla species complex, which consists of about 8 species that look very similar, but don’t actually interbreed with one another and can presumably be distinguished by genetic analysis. Back in 2011, I previously posted pictures of a similar green crane fly, but that one was a deeper green color and had browner legs, so probably not the exact same species.

The eyes are extremely black, and quite large compared to the rest of the head. The rest of the fly is so pale that it almost seems like it should be transparent, even though it isn’t. Still, it would be awfully hard to pick out on a green surface like a blade of grass or a tree leaf.

At first, I thought that my photos might be a bit blurry, but looking more closely I see that the fly actually is covered with fine fuzz, which blurs its outlines. The two green orbs sticking out to the side just behind the second pair of legs are the halteres, which are heavily modified wings that have been turned into a sort of gyroscopic balancing mechanisms. All of the flies in the order Diptera (which only have a single pair of flight wings) have the halteres, but they are way more obvious on this crane fly than on most other flies.

These are very distinctive flies, but they are only a little bigger than mosquitos. And unfortunately, since they are drawn to light, some people with light-lure mosquito traps catch these, and think that they are mosquitos. And then they crow about how effective their trap is, without ever realizing that they are only catching inoffensive and harmless crane flies while the mosquitos that they wanted to catch go free. So if your mosquito trap is filled with things that resemble mosquitos, but are green like this, they are not mosquitos.

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