In his autobiography Charles Darwin told the story of how he once during a collection trip had picked up a beetle in each hand and and put the 3rd one in his mouth and how the latter had responded by releasing an “intensely acrid fluid” burning his mouth.
Here is a similar story by Henry Pilsbry from an 1892 paper of his. In this case, the unidentified “rare specimen” was undoubtedly a snail.
It may be remarked that the custom of holding specimens between the lips is not so rare with field naturalists as fastidious persons might suppose. I confess to having once swallowed a small and very rare specimen while holding it for a moment. The creature was, alas! not my own property, and its outraged owner has not yet forgiven me.I don’t think I’ve ever put a specimen, snail or otherwise, in my mouth for safekeeping, but I do remember witnessing a friend cleaning the mud off of tiny shells by putting them on his tongue and then rubbing them against the top of his mouth.