Fleas are blood-sucking parasites. They live off the blood of their host and cannot reproduce without it. Fleas are not only a nuisance, but because they are blood sucking parasites, flea bites can cause irritation to almost all mammals, including humans. They are considered dangerous because they are vectors for diseases like murine typhus or plague. Full grown fleas are not able to reproduce without feeding. Therefore, in order for their survival, it is crucial for fleas to find a host to feed on.
There are about 200 different species of fleas all over the world. Most fleas are biologically similar in shape, size, and color. Minor differentiations of fleas can only be observed through a highly magnified microscope. Flea species vary by preference in their host. For instance, rat fleas are most commonly found on Norway rats, cat fleas on cats, dog fleas on dogs, etc. However, they are not limited to just one host and can be found on many mammals. The common species of fleas are the cat flea (which are also commonly found on dogs and are known to bite humans), the dog flea, the rat flea, and also the human flea.
Biology and Identification
Fleas follow a full life cycle: egg, larvae, pupae, adult.
The eggs of fleas are best made in warm and humid environments. That is why you may see a heavier infestation during the summer season whereas in the winter, there is a lighter infestation of fleas. Eggs have a smooth covering and may easily roll off of the fur in resting areas. Eggs will hatch anywhere from 1-24 days.
Larvae and pupae are known to be able to survive for months before feeding for the first time on their hosts. Larvae will emerge from their eggs and will feed off of such things as dust, skin flakes or the feces of adult fleas. Larvae will spin a cocoon around themselves. This sticky, protective covering will keep them dormant for several months and even up to an entire year, until they emerge as an unfed adult flea.
The developed pupa will remain dormant until they can detect a nearby host. Once they emerge, the full grown flea will look for a host and purposely remain there for the rest of their lives. An unfed flea is able to live for months without a host. Once the flea feeds for the first time, it is not able to survive without its host for more than a few weeks. The adult fleas are about 1.5 – 6 mm long, reddish-brown in color and are wingless insects that use their legs as a means of movement. They are laterally compressed meaning that they are flat from side to side. Their long, powerful hind legs and laterally compressed body are efficient for easy movement through the fur of their host. Hook like combs on their legs make it easy for fleas to grab on to the host. Fleas are also known for their tube like mouth parts which are specifically adapted to make it easy to feed on the blood of their host. Fleas have very small or no eyes which makes their eyesight very poor, however, they use their antennae to navigate through their environment.