Book 30, Question 63
What are leeches, and are they dangerous?
Leeches are flat, soft-bodied worms with a sucker at each end.
Some live in ponds and lakes. Most pond leeches eat snails and worms, and only a few kinds feed on the blood of animals. They swim by rippling their bodies and attach to rocks and plants. They're a part of a healthy food web, and fish and birds eat them.