My, Grandma, what big mandibles you have . . .
Mandibles
This one I did *not* find in the house![1] It was out front, crossing the road[2]. It was strong and fast, and I had to hold onto it pretty firmly to get that face shot.
Full body view
This is a specimen of the genus Calosoma, most likely Calosoma calidum (it's a bit smaller than Calosoma sayi[3], which lives further south than here in any case, but it could be Calosoma frigidum, which lives all through Canada and all around the Arctic[4]). One of the distinguishing features of this genus is the colored "punctures" on the wing covers, which in this specimen were gold:
Wing cover detail
These are evidently commonly referred to as "caterpillar hunters", they are definitely predatory. Oddly, it didn't really try to bite me, even though the mandibles look capable of taking a nasty nip out of somebody. They are quite common around here, just a few seconds after I captured this one I saw another one also making a dash across the road. Hopefully, I'll find one of the larvae of this beetle sometime soon, they are these black, evil-looking things that closely resemble the beastie that got put into Chekov's ear in "Star Trek II: Wrath of Kahn". In the past, we've seen several of the larvae crawling around in the driveway, but not since we got the camera.
I was a little surprised to find out that these beetles live a long time - a year or so as a larva, and two or three years as adults. In any case, if they help keep down the caterpillars around here, I'm all for it.
[1] Just an update on how the arthropod project is going: So far, I've found 35 distinct species, and all but 4 or 5 were things that had gotten into the house or were sitting on the window (or, in today's case, crossing the road[2]). I haven't really even started hunting around in the grass yet.
[2] Q: Why did the beetle cross the road? A: To get its picture on the Internet!
[3] In North American entomology books, you'll see a lot of reference to the name "Say", usually identifying beetle species. These are references to Thomas Say, who was one of the first serious naturalists in North America. With a combination of hard work and being in the right place at the right time (the Midwest, in the early 1800s), he identified over 1400 new species of insects (over 1000 of which were beetles). He is reported to have held the record for most species identified by a single individual, even though he died when he was 47 years old.
[4] One of the things that struck me about this beetle is that it was very cold-resistant. I did the normal trick of putting it in the refrigerator to slow it down for photography, and even after a couple of hours it was still scrabbling slowly at the sides of the jar trying to get away. This same treatment knocks out other insects to the point that they barely move until they warm up. The cold-hardiness makes me think that it might be the semiarctic species.