Horned passalus, or Bess beetle, Odontotaenius disjunctus. The light-colored ones have just emerged from the pupal stage; the black ones are older. Very common in forested areas, but seldom seen. Check the link below, and thanks for the picture.
Tucker

Here is a link that might be useful: Horned Passalus

Thanks so much for the ID and the link, Tucker!
I live on 5 1/2 mostly wooded acres in southeast Mississippi. We lost hundreds of big trees in Hurricane Katrina, and I put a lot of the resulting log sections around newly planted trees to keep armadilloes from digging them up. It's been 2 years since the hurricane, so the logs are extremely rotten, with mushrooms all over them. These particular logs are in an area close to the house that I mow. Anyway, I put the beetles back at the base of the log they were under when I got through mowing that little area around the logs - they're big and interesting looking! I noticed what might have been a larva running hurriedly by - it looked sort of like a centipede.
Thanks again!
Sherry