Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Nuclear Bug - Diogmites basalis

Nuclear Bug - Diogmites basalis
Northfield, Franklin County, Massachusetts, USA
Size: 3/4"
This creature looks somewhat like a Robber Fly, but is twice the size. Of course, I do live close to a nuke plant.....
What IS this thing??

Images of this individual: tag all
Nuclear Bug - Diogmites basalis Nuclear Bug and prey - Diogmites basalis

Yes on Robber Fly, maybe Diogmites?
It is a Robber Fly. Might be Diogmites. That "hanging out while snacking" is typical for them, but I am just learning a few. That dark pattern under the abdomen is quite different than species I've seen in NC.

Check out Herschel Raney's pages on Diogmites. D. platypterus is very dark, looks pretty similar to your photo. (Legs are more yellow.) Again, these things are tricky, I'm looking at patterns and colors, which are often not reliable.

Again, that's if I am in the correct genus!

Patrick Coin
Durham, North Carolina

Thanks Patrick-
According to my Audubon guide, Robber Flies are 3/8 in., which is what's been making me wonder, as these guys are a lot bigger. I know there is a species of Giant Robber flies, but the pics of those I've seen don't quite match these. Soon I will add a pic of a similar fly that looks, to me anyway, different enough that I'm not sure it's the same bug. Thanks for the link- we'll see how things develop. Right now, I'm going with the leaky nuke plant theory. It would explain the three foot long ants I've been seeing.....
Bruce Kahn

Nuclear bug
That is indeed a robber and there are many larger than 3/8 inch. Several reach 35 to 40 mm and the Diogmites are almost all larger than 18 to 20mm. This is not Diogmites platypterus unless the leg color is very variable in your section of the country. It is likely Diogmites basalis and that is described as a "large reddish brown species" with dark reddish legs. They are supposed to have a golden spot on the abdominal sides and your spots qualify though they are smaller than I expected.

A plethora of Robber Flies
Thanks Herschel-
After checking out your site, I see that there are indeed more varieties of Robber Fly than are dreamt of in my philosophy.... or more than one way to skin a cat... or at least more than you can shake a net at....
So much for the Audubon Society! Bunch of amateurs....
Bruce Kahn