Lots of interesting stuff on this thread
.
Found the following via Google Scholar:
http://psyche.entclub.org/82/82-292.html
which is based on observations of captive beetles in America, with the Devil's Coach-horse (
Ocypus olens) larvae and adults preying on the garden snail (
Helix aspersa).
Doesn't go into a lot of detail about the feeding habits but includes:
"Generally, the shells were left intact. However, some of the smaller shells showed various degrees of destruction from the body whorl to the apex. Attack by an adult beetle resulted in more severe mutilation of the shell."
Martin
Martin Harvey