How Fleas Work

An adult flea.
Photo courtesy CDC/Vector Ecology & Control Laboratory, Fort Collins, Colo.

Imagine returning to your home after a long vacation. You pick up your pets from the kennel, unload your luggage and head to bed to recover from the long drive. But your sleep is anything but restful. All night, you're plagued by tiny pinpricks and incessant itching. It doesn't take you long to figure out that you're being attacked by a seemingly infinite mob of hungry fleas.

­ What happened? Did your pets pick up an infestation at the kennel? Did the vampire-like insects hitch a ride on your luggage? Or did a swarm of them decide to move in while you were gone?

It's a creepy idea, but the most likely answer is that the fleas were waiting for you. Fleas are parasites -- or life forms that feed on hosts -- often harming the host in some way. Fleas use their hosts' blood as food. They generally prefer the blood of four-legged animals to human blood, so before you went on vacation, the fleas fed on your pets, not on you.

Although newly emerged fleas need to find food within a few days, adults can go for a couple of months without a meal. Flea pupae can also stay in their cocoons for up to a year, waiting to sense the body heat and vibrations that signal the presence of nearby hosts. So when you go on vacation, the fleas don't starve to death -- they simply wait for you and your pets to come back.

When you walk into your home after being away, hungry adult fleas flock to you and to anything else that has a pulse, regardless of how many legs it has. Pupae break out of their cocoons and search for their first blood meal. Your home, which seemed clean and relatively flea-free when you left, is suddenly overrun.

The ability to live without food is just one of a flea's many adaptations. These adaptations make it easier for fleas to move around on their hosts, feed on blood, reproduce and survive when food is scarce. In this article, we'll look at how these adaptations make it harder to kill fleas. We'll also explore how to keep fleas from invading your home and your pets, as well as how to get rid of an infestation.