Fleas are one of several pests that feed on blood. Others are mosquitoes and other biting flies, ticks, bed bugs, certain mites, and lice. While fleas need animal blood to survive, they can also go for several months without feeding…just one reason why they are such successful pests.

Adult fleas spend all of their time on their host animal and are well adapted for doing so. They are flattened side-to-side so that they can move between animal hairs. Each body segment has backward-projecting spines (like a comb) that help the flea hold securely to the hair. The flea’s head even has spines to hold it in place while it is feeding.

Flea to Rover: “I Vant to Suck Your Blood!”

Fleas, like most of the blood-feeding insects, have piercing-sucking mouthparts. A flea’s mouthparts are made up of three stylets that pierce the skin. The two outer stylets work in unison to saw into the skin, causing bleeding. Once the skin is pierced, a third stylet is inserted and all three form a feeding tube that draws up the blood. The flea injects saliva into the wound to keep the blood from clotting. If this particular flea is carrying a disease, that disease is introduced into the victim through the flea’s saliva.

A mated female flea has strong incentive to feed since she must have a blood meal in order to develop eggs. She will consume about 18% of her body weight in blood, and will then lay 4-8 eggs which fall off of the animal host. She will feed every day or two, producing 400-500 eggs in her lifetime. The male flea feeds on blood, too, but the immature or larval flea that is not found on the animal does not suck blood. It feeds on dried blood, though, in the form of feces excreted by the adult flea.

How Can You Tell if the Bite is From a Flea?

Fleas prefer animal blood but will feed on people if there are no pets or other animals available (see How Can I Keep Fleas From Biting Me?). Unfortunately, there is no easy way to distinguish a flea bite from any other insect bite. People have varying reactions to flea bites. For most, a flea bite leaves a small red spot where the mouthparts entered the skin surrounded by a slight, hard bump and reddish discoloration. Some people barely notice the bite while others have intense itching which can last for several days. Sometimes a rash develops. Flea bites on people tend to be more common on the lower legs.

Photo credit: Ikayama / Foter / CC BY-NC-SA