An adult flea is a small reddish-brown bug that is laterally compressed. This means that the bug is not very wide in order for it to move more easily between the hairs of animals. Fleas also have small spines on their body's that prevent them from being brushed off of the host. Additionally, a flea has a hard, outer body that prevents it from being smashed. Because of these adaptations, it can be difficult to kill them.
Fleas are parasites that feed off of blood, both human and animal, by piercing the skin from the outside and sucking blood. Because they do not have wings, fleas travel from hosts by hopping. They can hop up to 7 inches in the air.
Fleas are a pest that many pet owners have had to deal with at some point in time. Because many species of fleas prefer to feed off of animals, pets are the most common method for fleas to infest a household. Although fleas prefer animals, once inside a home they will often bite and feed off of humans as well.