Robber Fly

Subject: Is this a robber fly
Location: Princeton NJ
July 30, 2017 4:37 pm
I have never seen a fly like this. It’s about an inch long. I tried to find it on the Web, but the closest thing I could find is a robber bug. Is that what it is?
Signature: Barbara

Robber Fly

Dear Barbara,
Thanks to this BugGuide image, we are confident your Robber Fly is a male
Efferia aestuans.  According to BugGuide:  “The most likely robber fly to land on humans. (comment by Herschel Raney)  Sometimes fearless. The males are much less common and harder to approach. (comment by Herschel Raney)  The commonest species of Asilinae in the northeast (comment by Herschel Raney).”

Thank you Daniel. Are these beneficial insects, are should I kill these when I see them. I accidentally squirted it with the hose, and it just sat there looking at me. With insects, I try to identify them if they are new to me. I’m an organic gardener, and I rely on benefical insects.

Hi again Barbara,
Robber Flies are beneficial predators.  While they might bite a person if carelessly handled, they are not aggressive.  We do not condone killing Robber Flies.

Thank you! If I ever see it again, I will let it be. We have honey bees, but we can spare a few. We also have hummingbirds and hummingbird moths. Hopefully the robber fly will not bother those.
Thanks again. I really appreciate your service.

We believe your hummingbirds and moths will be safe as they are probably too large for this species, however we do understand that large Robber Flies can attack hummingbirds, something you can read about on Hilton Pond.

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