I do see this in the "known bugs" section, but I decided to revive this thread just to point out that the bug still exists in trainer at least. It's not specific to PUing your own scarabs, either...
Gemini PUd a total of four scarabs during that game and ate a total of three of mine. When he PUd his first, the scarab health was way high, it might've been higher than all scarabs played in the game. And then it didn't drop to 1 at the end of his turn.
Again, sorry for reviving the dead thread but I'm certain this is not the way the developers intended PUing scarabs to work. If I meet him again I'll keep closer track.
Edit: Elidnis PU's my 6/13 scarab when I have 10 and he has 0. It drops to 6/4 at end of turn (should be 6/1). A few turns later he PUs the same scarab (now 6/25) when I have 23 and he has 0. It drops again to 6/4 at end of turn (should again be 6/1).