Robber Fly – Laphria thoracica

Family Asilidae – Robber Flies
Live robber flies photographed at northern Illinois. Size = 25mm / deer fly prey size = 10mm

The 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.

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!

There are over 7,000 species of robber flies world wide; nearly 1,000 in North America.

Male Bumble Bee

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: Bugguide.net Laphria thoracica

Flies Main | Flies Index | Bee Flies | Robber Flies

Tree Encyclopedia / North American Insects & Spiders

Online since 2002