weird fly from the philippines (1)
December 27, 2009
Dear Bugman,
What is this bug?
It is very common in gardens. Its distinctive characteristic is that it constantly waves its two front legs around (white-tipped) as if engaging in semaphore.
It must be some kind of fly, but which one?
Thanks for the attention!
Luzon, Philippines

Stilt Legged Fly

Stilt Legged Fly

Dear Kulisap,
We tried doing a web search of “fly waves front legs” and came up with a cirrusimage page on the Stilt Legged Fly family Micropezidae that states:  “I would have called this the ‘semaphore’ fly, in that it constantly waves its front legs around as if signaling someone or something. Popular science has it they are mimicking ant or wasp antennae, but I’m not sold on that theory. Wasp antennae are jointed and “droop”  and certainly don’t wave about like this fly does.
”  According to BugGuide:  “Odd little flies, known for their displaying (?) behavior of walking around and lifting their prominently marked front legs. Abdomen attached to thorax by “wasp-waist”. Likely ant or wasp mimics. The posture of the forelegs may imitate ant and/or wasp antennae and provide them with some protection from predators.”  It is interesting that both you and the person who wrote the cirrusimage posting likened the behavior of the fly to semaphore.

One Response to Stilt Legged Fly from the Philippines

  1. kulisap says:

    Dear Bugman,

    Thanks for the response and the positive ID!!

    I do agree with the information you quoted… I don’t think they are wasp mimics, since I’ve never seen wasp antennae move around as much as these flies’ legs do! What’s more, all individuals I’ve observed engage in the same energetic movements, so I kind of doubt that it’s for sexual signaling.

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