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.

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.

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

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

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.)

More about thick-headed flies

• Thick-headed flies on bugguide.net
• The enemy within (find out how and where the females lay their eggs)
• Parasite forces host to dig its own grave (specifically about bumblebee victims)