They are small- most of them are less than one centimeter long. They don't look dangerous and they can't kill you, but most people are afraid of them. What are they?
They are leeches, small animals that live on the forest floor and drink blood. Most of the time they drink animals' blood but they are happy to drink human blood too. As soon as they find an animal, they sink their teeth into the skin and drink the blood. The leeches can drink as much blood as more than three times their own weight. When they're full, they drop off and find somewhere to rest for half a year! Each time the leeches drink blood, it can keep them alive for six months.
Just why people are so afraid of leeches is difficult to say. Maybe it's because they drink blood. But they are quite useful too. Doctors use them during operations. The leeches help doctors by drinking blood around a cut. With less blood there, the doctors can see better what they are doing.
