#thick-headed fly

[northerlyy]

Thick-headed Fly (Physocephala tibialis), taken June 12, 2026, in Georgia, US

A very cool-looking fly resting beside a busy flower cluster! This species is such an awesome case of mimicry—I could tell what this guy was trying to be immediately. Most wasp-mimics go for parasitic species or paper wasps, but this species went for a potter wasp. The dark cells of the wing that form the shape of a wasp's wing are especially cool, likely to make it so birds will only see the wasp-like wing silhouette from afar and steer clear of this fly. Like most wasp mimics, they feed on the same plants as their models and likely move similarly, further selling the act!

[dailybugfacts]

Could you give some facts on Physocephala tibialis and other eastern U.S. conopid flies?

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TODAY'S FACT IS

Did you know that Physocephala Tibialis is a species of thick-headed fly found in much of the eastern US and southeastern Canada? These flies parasitize bees going around pollinating flowering plants. The fly lays an egg in the abdomen of the bee victim, eventually hatching and developing the larva of the fly inside the abdomen of the bee host. Occasionally, the host bee will literally dig its own grave shortly before the developing larva kills it. The larva pupates and overwinters in the corpse of its host and eventually goes off as an adult to continue the cycle.

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Photo by Heather Holm

[miyrumiyru]

They looks like a wasp chewing a toothpick

[have-you-seen-this-animal]

Conopid fly mayhaps?

Have you seen a conopid fly (Family: Conopidae)?

I have now

Yes, in photos/videos

Yes, irl

I'm not sure

Voting ended onJan 8, 2025

Photos thanks to the wikipedia commons and Marlin.

[miyrumiyru]

Love on a leaf!

Not gonna lie, this situation is kinda... hot.

조잔벌붙이파리 (Conops flavipes)

[miyrumiyru]

Family Conopidae (Thick-headed flies)

Females are parasite the bees (especially to bumblebees) by opening the victim's abdomen like a can (＠_＠;)

Adults feeding on nectar :P

(F) 산타로벌붙이파리 (Conops santaroi)

(F) Waisted beegrabber (Physocephala rufipes)

[coolbugs]

Bug of the Day

Check out this cool thread-waisted wasp I found in my pollinator garden the other day!

(Just kidding, it’s a fly, not a wasp - a thick-headed fly, Physocephala tibialis. Did it fool you? It was definitely trying to ;-))

[kqedscience]

Parasite Forces Host To Dig Its Own Grave

"If a bumblebee is attacked by a thick-headed fly, it’s doomed. The fly will lay an egg inside it and the larva will eat it alive. And if that wasn’t an ignoble enough fate, the larva also forces the bee to burrow into the ground. The soil is warm and safe, and makes for a better nursery for the developing fly. And the bee? The bee is as good as dead. For its last act, it might as well dig its own grave."

Learn more about this parasite from Ed Yong at Not Exactly Rocket Science.