Thick-Headed Fly – Physocephala

Thick-Headed Fly – Physocephala furcillata

Conopids are most frequently found at flowers, feeding on nectar with their long proboscis.  Conopidae is distributed in all the zoogeographic regions except for the poles and many of the Pacific islands. About 800 species are described worldwide, approximately 67 of which are found in North America.

If you’ve ever seen one of these flies, you’ll know how the word ethereal applies to its habit. The above specimen is only about 10mm – much smaller than the individual pictured below, which is about 15mm.

Conopid Fly

Live adult flies photographed in the wild at Allegheny National Forest, Pennsylvania. Size = 10-15mm

Thick-Headed Fly - Physocephala tibialis

This species’ wings are colored to mimic the dark, narrow wings of the vespid wasps, especially the potter wasp (below).

The majority of conopids are black and yellow, or black and white, and often strikingly resemble wasps, bees, or flies of the family Syrphidae, themselves notable bee mimics. The larvae of all conopids are internal parasites, most of aculeate (stinging) Hymenoptera. Adults are said to alight and deposit eggs on their flying hosts.

Physocephala tibialis
Potter wasp mimic
Vespidae - Potter Wasp Eumenes sp.
Potter Wasp Eumenes sp.

Thick-Headed Fly - family ConopidaeAn insect’s world is a colorful place!

Flies Index

North American Insects & Spiders

Online since 2002