When I first saw this bug, I was admittedly worried. It looked like it was about to burst, and maybe it was. Apparently judging by one entry on BugGuide.net, I’m not the only one who’s come across this particular kind of female beetle with the dire-looking abdomen. In fact, I noticed quite a few entries with ballooned Ophraella sp. beetles on BugGuide. The one subtle difference in their shots versus mine was that in mine the abdomen is bi-color, with a yellow and dark brown/black divide, while the BugGuide shots were more or less one color, usually yellowish or brown. My uneducated educated guess is that this individual is in a later (or earlier) stage of development.