Bumblebee Mimic Robber Fly

2014 June 4

I see that this one didn’t get written down in my log book, so I’ll have to go by memory and the date stamp on the image files. The pictures were taken on July 5, 2013, and I think that either I found it dead in the road, or Sandy found it dead on the sidewalk.

At first glance, it looks like a bumblebee, but appearances are deceiving. Note that it only has one pair of wings, with the hind wings reduced to “halteres”. So, we know immediately that it is a fly (Diptera), and not a bee.

The head also looks decidedly non-bee-like. Bees tend to have smaller eyes relative to their heads than flies do.

The proboscis is clearly designed for stabbing, and so this looks like a predatory fly. The legs are also quite robust, which would have made it pretty good at grabbing onto prey.

What it actually is, is a robber fly mimicking a bumblebee. While there are several robber fly genera that mimic bumblebees, it looks like only the genus Laphria lives this far north. There are quite a number of these, but based on abdomen color, leg color, and the absence of a tuft of yellow hair on the face I think the most likely looks to be Laphria sacrator

The normal reason for mimicking a bumblebee would be as protection against predators who don’t care to get stung. But, given that these are predatory flies, they might have another reason. It might be easier to ambush actual bees on flowers if they think the robber fly is just another bee. As long as the fly is quick, and avoids the bee’s stinger, they could take one easily. And, in fact, some of the larger bee mimic robber flies are referred to as “bee killers”

It looks like robber flies in general lay their eggs either in the soil or on plants, and the maggots that hatch out are usually predatory on other small insects that they find.

One Response
  1. Bridget permalink
    June 6, 2014

    Saw one of these for the first time last night at a local park. I live in Columbus, Ohio. It was really cool!

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