Back biters are people who gossip or talk behind someone's back. The term can also be used to describe animals that bite from behind, such as fleas, MOLARS, and bumblebees. Fleas are small, wingless parasites that feed on the blood of mammals and birds. MOLARS are the large, flat teeth at the back of the mouth used for grinding food. Bumblebees are large, fuzzy insects that live in colonies and feed on nectar and pollen.