Bumble Bee Mimic Robber Flies

Here are a couple Bumble Bee Mimic Robber Flies I ran across a couple months ago. And while it may look like they had an argument and are disdainfully looking away from each other, they're actually mating. Although there could be exceptions, in general I believe flies (including robber flies), butterflies/moths, and true bugs tend to mate with the ends of their abdomens connecting, while with beetles, mantises, and grasshoppers the males mount the females. (Yes, I've seen a fair amount of "insect porn" out there - these guys are shameless.)

These flies are a little unpopular in some circles because:
  1. We've been told we need to protect bees.
  2. These robber flies actually eat bees. (I suspect they'll eat bee relatives we tend to feel less empathy for, like wasps/hornets, unless the wasps/hornets are substantially bigger than our bees.)
Note that I don't see enough robber flies that I believe they're having much of an effect on bee populations. My guess is that a single lawn treated with insecticide probably hurts bees more than all the robber flies in a township. (Still, I have to admit that sometimes when I think I'm seeing bees, I may actually be seeing this type of robber fly.)

You could easily mistake these robber flies for bumble bees or Carpenter Bees; they are considered mimics because they derive benefits by looking like (some) bees:
  1. Some predators might avoid them because they fear they might get stung by the robber flies, even though robber flies can only bite, not sting. This is called Batesian mimicry.
  2. Looking like bees might help them casually fly next to a bee that thinks they're harmless relatives rather than bee predators. This is called aggressive mimicry.

June 17, 2021 at the Plainsboro Preserve
Photo 141960280, (c) jpviolette, some rights reserved (CC BY-NC)


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