Why, snails, of course! The Times is reporting that in Great Britain unprecedented numbers of snails and slugs have been crawling into the mail boxes to dine on the mail. Not only that but they also leave everything covered with their slime!
The Times quotes a Post Office manager: “Slugs and snails are devouring the edges of letters and most of the stamps. They are everywhere at the moment because of the weather. All we can do is apologise to people and keep on putting the pellets in the box.”
Snails and slugs do eat paper. And despite the Royal Mail's claim that the mollusks are after the glue and the printing inks, it is actually the plain paper that they wouldn't mind eating. Paper is mostly cellulose and cellulose—from the plant matter they eat—is a major component of the normal diet of most snails and slugs.
That's is exactly why one should not put the locality information written on paper in the containers of live snails and slugs even if they are dormant. I try to follow my own advice, but there are occasional lapses. Here is a recent example. The corner of this locality tag was eaten away by the very slug hanging upside down underneath the lid within a few hours it took to bring it home.
Thanks to the reader xoggoth for bringing this news item to my attention.