Robber Fly – Laphria thoracica

Robber Fly – Laphria thoracica

color photo Robber Fly Laphria thoracicaFamily Asilidae – Robber Flies
Live robber flies photographed at northern Illinois. Size = 25mm / deer fly prey size = 10mm

color photo Robber Fly Laphria thoracica with deer fly preyThe backwash from this sucker’s prop almost knocked me down yesterday when it did a close fly-by with a stunned deer fly held tenderly in its front claws, impaled on its proboscis. This is the largest (and in my opinion most stately) of the Laphria complex flies, a truly magnificent creation.

color photo Robber Fly Laphria thoracica with deer fly prey

Before I began photographing insects, I had no idea such a thing existed. Now it is my ardent wish every time I’m in the field for an opportunity to watch one of these clever creatures at work.

For me, such a spectacle is every bit as fascinating as watching a lion or cheetah capture and consume a large mammal; a less dangerous pursuit certainly, accessible and inexpensive!

color photo Robber Fly Laphria thoracica with deer fly preyThere are over 7,000 species of robber flies world wide; nearly 1,000 in North America.

Male Bumble Bee
Male Bumble Bee
Robber Fly - Laphria thoracica
Female Robber Fly

The Laphria complex flies are convincing bumble bee mimics. This evolutionary adaptation allows them to reap the benefits of aposematic (warning) coloration without the high metabolic cost of constructing and maintaining a venom-delivery system.

Reference: Laphria thoracica

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Online since 2002