Robber Fly from Montana

Subject: Northwest Montana Bug?
Location: Northwest, Montana
October 16, 2016 8:35 pm
This bug was on the wall at a store, in Northwest Montana, USA. It also seemed somewhat aggressive.
Signature: Danielle Peirce

Robber Fly, possibly genus Stenopogon
Robber Fly, possibly genus Stenopogon

Dear Danielle,
This is a predatory Robber Fly in the family Asilidae, and it greatly resembles this member of the subfamily Stenopogininae that is pictured on BugGuide.  In our opinion, it seems to resemble members of the genus
Stenopogon that are pictured on BugGuide where it states:  “diversity about equally divided between Eurasia and N. America (w. Canada to Costa Rica); in our area, mostly sw. US (the wast majority restricted to CA), with 3 spp. more widely western, ranging into ND-IA-MO-AR.”  The only species that BugGuide reports from Montana is Stenopogon inquinatus, and your individual might be a member of that species when compared to this BugGuide image.  Large Robber Flies are able to take down large winged prey, including Dragonflies, Bees and Wasps, but they are not aggressive towards humans.  With that said, carelessly handling a large Robber Fly, if a person is even able to capture one, might result in a painful bite.  Random Natural Acts has some very nice images of large Robber Flies.

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