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Of the 650 species of leech listed, Hirudo medicinalis is one of the most extensively studied. This annelid from the subclass Hirudinea has 2 suckers, one housing the mouth and its 3 jaws. It lives mainly in the stagnant waters of marshes and ponds. When it comes to reproduction, the animal is a hermaphrodite. Inseminated leeches lay their eggs during the spring and summer months, outside the water, with cocoons containing as many as thirty young.
Cockroach Species. There are over 3,000 different types of cockroaches-some are considered pests while others are beneficial in their natural environment. The three main types of cockroaches commonly found in homes in the U.S. include the German cockroach, Oriental cockroach and American cockroach.