I noticed the indented thorax in bees of an observation hive of mine.
Also visible on these bees were varroa mites, although only a few
mites.  The obs hive population is also very small due to (I think)
swarming several times during the summer.  I have no idea what may
have caused the dent.  By the way, I didn't mention, the dent is on
the underside of the bee.
Eileen Gregory
Hillsborough,
North Carolina