In addition to their medical use, the leech was also used in Victorian times by sailors, who used them to detect impending storms.

A contraption existed where twelve leeches were placed in bottles, with small plates attatched at the top which, when knocked slightly, would ring a bell. The theory was that when a storm approached, the leeches would react to the change in air pressure, and instinctively attempt to seek cover by climbing out of the bottle. They would then knock the plate, ringing a bell.

The idea was eventually scrapped because of the fact that the leeches had to be fed periodically, and also because the sailors were reluctant to place their lives in the "hands" of a bunch of parasites.