Sunday, August 3, 2014

A Fly in Bee's Clothing

The robber fly, Laphria flavicollis. Click to enlarge.
Looks like a bee, doesn't it? It's not.

Bees have two pairs of wings. See the yellow ball-on-a-stick just in front of the right wing? That's called a haltere organ; there is another one on the other side. Halteres are the modified remnants of an ancestral pair of wings. All flies have halteres but they are easier to see on big flies like this one that's just over half an inch long.

The antennae are all wrong, too. Look at the real bumblebee below for comparison. And, although this insect looks superficially like a bumblebee, it is sitting on a leaf. That's an unlikely pose for a bumblebee -- they rarely sit still for long.

Robber flies are predators that prey on insects -- beetles, flies, BEES, and even big things like damselflies. They can catch flying prey in the air, snatch them up, and carry them away to eat. Robber flies have strong beaks with piercing mouthparts that they jab into prey. They inject digesting enzymes that liquify the victim's insides. Then the fly drinks them up through its straw-like mouth.

And what is the point of looking like a bee? Maybe it puts bees off their guard and helps the robber flies catch dinner.
This is a bumblebee. If you see what seems to be a bumblebee sitting on a leaf, take a closer look. It might turn out to be a bee-like robber fly! Click to enlarge.

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