Last Updated: December 30, 2016

Fleas are any of over 2,000 bloodsucking parasitic species in the order ‘Siphonaptera.’ In greek, ‘siphon’ means tube, referring to the tube through which fleas suck blood, and ‘aptera’ means wingless. Fleas are very small (1/16th to 1/8th of an inch) wingless parasites that feed off of the blood of mammals and birds. Fleas are generally dark colored, ranging from reddish-brown to black. They are fast and very agile, able to jump nearly seven inches (over one hundred times their body size!). This agility allows fleas to move between hosts with relative ease. Fleas have very thin bodies with bristles facing backwards to allow them to move rapidly between the hairs or feathers of their host. In addition they have durable bodies, which make them resistant to scratching and swatting.

Fleas lay eggs directly onto their hosts, about twenty at a time. The eggs then generally roll off in areas where the host sleeps. Eggs hatch into small larvae that feed on food around them including feces, rotting food, and rotting animals. The larvae are blind and like to stay in small dark places like cracks in walls, sand, and linens. After a few weeks, larvae become pupae and after another few weeks, adult fleas emerge out of the pupae. Fleas can survive the winter by staying in the pupa phase of their life cycle. Some fleas emerge from their pupae only when they sense a potential host is near.

Adult fleas are relatively long-living insects, able to live for several years in ideal conditions and to go for several months between feedings. Female fleas can lay thousands of eggs in a lifetime, allowing for tremendous population growth. Adults generally make up a minority of any flea infestation. The majority of the population at any given point of time is the eggs. Fleas thrive in warm and very humid environments. Flea bites though not generally painful can become itchy and swollen. Fleas can be dangerous as transporters of disease. Some of the most common fleas are dog fleas, cat fleas, and human fleas. There are hundreds of fleas capable of feeding on human blood. The human flea (pulex irritans) is one such flea. Despite its name, the human flea is actually capable of feeding on dozens of different mammals and birds. As with most fleas, it is possible for the human flea to transfer various diseases and parasites.