Leech (Hirudo medicinalis)

Last summer, on a family trip to the lakeside, I spotted a leech near the waterline where we were snorkeling. I was startled and disgusted. The last thing I'd want was a leech hanging on my skin, sucking blood. That was the end of

playing in the water for that day, but I decided to find out a little more about the critter.

This is what I spotted, in fact a horse leech (haemopis sanguisuga), a very common species. It can grow up to 15 cm long. It feeds on small aquatic animals and does not suck blood.

Leeches are typically black or brown worms that have two suckers, one at each end. A majority of leech species live in fresh water. They feed on the blood that they suck from vertebrate and invertebrate animals. Because of their hunger for blood, many people (like myself) find these wrigglers unpleasant, even frightening and disgusting. However, most leeches do nor feed on human blood, and are quite harmless to humans.

Throughout history, leeches have been used in medicine for blood-letting, removing bad blood from patients. The practice was in use in ancient Greece and India, and -although rare nowadays- leeches are still used for this purpose in some parts of Europe and North America.