A convincing wasp mimic

While wandering around the wildflower garden late last evening, I noticed a small black insect resting on a bee balm leaf. My first thought was that it could be the offspring of the potter wasp I observed a month ago since it was smaller than the wasp I saw in June.

side view of a thin black insect facing to the left, with a white bands on waist and two on abdomen

But I have been fooled by flies that look like bees many times, so I decided to look closer. And sure enough, the antennae were short – a big clue that it’s a fly.

top view of the insect, with the two small antennae at the top

And then I noticed the big eyes – another clue. In fact, these almost look like cartoon eyes.

view from the front, with two large eyes and two large white spots in the middle

Diagnosis: thick-headed fly, possibly Physocephala furcillata. It’s a parasite that indirectly kills bees when it lays its eggs.

top view with the head facing left, showing the narrow waist

This fly is so similar to a wasp, on first glance, that I had to double-check my images of the potter wasp to make sure I hadn’t overlooked a key feature on that one, but I’m still convinced on the potter wasp. (Plus, I don’t think flies build pots.)

comparison of fly vs. potter wasp - hard to see wasp's antennae but heads are different

More about thick-headed flies

 

 

 

 

 

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