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Opisthius richardsoni

Opisthius richardsoni
Milwaukee, Clackamas County, Oregon, USA
April 4, 2009
Size: Approx. 1 cm long
Found on the banks of a large river, muddy & sandy. Ran like a tiger beetle, but did not fly. Possibly an Elaphrus? but couldn't find a good match among existing records.

This is a specimen of Opisthius richardsoni, a close relative of Elaphrus. Welcome to Bugguide! Nice to see another contributor from my home state (I grew up in Portland).

Thanks Eric! I use your book
Thanks Eric! I use your book all the time. This species isn't in there, nor in any of the other field guides I have. Are they unusual? I think I've seen them before, but always thought they were tigers.

Only so much room on the "book ark."
I wanted to include a lot more species than we were able to in the field guide:-) No, this species is not unusual or uncommon, just often ignored, so not many images exist.

Maybe "locally" common?
I've only ever seen them in one locale--a sandy, rocky riverbank--and never in a number of similar locales that do house tiger beetles.
On the other hand, they seem abundant there. It could be because of the particular size of rocks with adjacent sandy areas where they become visible.

ID Progress
I went through the same process: first I thought it was a tiger beetle, then found a photo misidentified as Elaphrus, finally got a good ID.
They do run a bit like tiger beetles, and the ones I've photographed coexist with two species of tiger beetle.

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