Horse Fly Mimic?

July 11. A late morning walk to the St Olaf Natural Lands. I noticed a lot of conspicuous galls on some Sumac. These are caused by Sumac Gall Aphids, one of the only aphids known to cause galls; usually galls are caused by flies and wasps.

Encountered, at the same location and possibly the same dead branch as four years ago, Astata unicolor. The large eyes and odd behavior of this wasp convinced me, at first, that it was a horse fly or a soldier fly. It even had the high-pitched whine of a fly when it flew. Perched about four feet off the ground on a dead Sumac branch, this wasp made rapid, aggressive flights, returning again and again to the same perch---a male being territorial. The females of this species, a stinkbug hunter, differs markedly in appearance with smaller eyes (not meeting in the middle) and red abdomen.

At the Cerceris fumipennis site, the playing field was being groomed, a small vehicle driving around and around the infield, smoothing out the playing field, erasing all the wasp nests. I found one wasp with beetle sitting on the ground where the entrance to her nest used to be. I suspect most of the wasps will be able to re-establish their nests and entrances.

Posted on July 12, 2017 12:16 PM by scottking