Handsome little fellows, aren't they? These are known as Horned Passalus, Odontotaenius disjunctus. Another name is Patent Leather Beetle; kind of a good one, that. These were in the midst of rotting wood, where they spend their lives. Supposedly, adults can make up to fourteen distinct sounds by rubbing various body parts together, and will "vocalize" when disturbed. We weren't overly abrasive with these, apparently not enough to stimulate them to call. The brown beetle is a youngster; it will eventually grow into a suit of gloss black like the full adult behind it.
Horned Passalus larvae are big white grubs, nestled deep in galleries made by the adults. The youngsters cannot feed, so the adults handle the chore of feeding them. The formula for baby? Partially chewed and digested wood chips and feces. Great stuff. But they'll do just fine on that, if a Pileated Woodpecker doesn't key in on their log and blast it to smithereens. Nothing one of those jumbo woodpeckers would like better than a giant beetle grub.
A closer view of the adult. They have rather intimidating pincers, but seem to be quite docile and made no effort to do any of us in. Upon close inspection, most large beetles are quite showy, even all black ones like this. Notice the tan fringe of hairs at the rim of its pronotum, which is that helmetlike covering just in front of the groovy wings.
We found this one nearby, and it is a real showstopper. Unfortunately, I could not manage a free-ranging photo. This beast, which we believe to be a Blue-margined Ground Beetle, Pasimachus depressus, was astonishingly fast. No joke. If released, it would scoot like it had been shot from a cannon, leaving no chance of decent photos. This style befits its lifestyle as a hunting beetle that runs down and eats other critters. It is aided in this by large pincers, although it made no effort to give us a bite like some other big, pincered beetles will. Maybe it felt that the foul-smelling secretions that it blasted from its anal glands would be sufficient to deter us.
Unfortunately, some large beetles have become scarce, at least locally, because collectors covet them. There is a thriving and probably mostly unregulated trade in beetles, with some of the largest and most beautiful species fetching hundreds of dollars. Many if not most are harvested from the wild, too. This probably isn't an issue, at least yet, in Ohio, but species like the Hercules Beetle of the tropics have been decimated locally by collectors.