1) I'd be surprised if there were meat enough on the tribble to eat. Considering how little energy they need in order to reproduce, I figured they were a reproductive system with legs and little else. They're not seen moving, so I wonder if they even have locomotive capabilities or rely on people getting angry and throwing them far away . . .

2) They could also be considered akin to fish, making them parve. It's never stated what the original natural habitat of tribbles looked like, so far as I'm aware (other than that it was filled with baby tribbles). Not that they have fins and scales, but the locust comment seems apt.

3) I also have this image of a chinese chef "Poison . . . poison . . . tasty tribble!" (http://en.wikipedia.org/wiki/One_Fish,_Two_Fish,_Blowfish,_Blue_Fish)