The Pulex irritans is a common flea better known as a human flea and is very similar to cat fleas and dog biting fleas on humans.
Body Structure of Human Fleas
Most fleas have the same general body structure with minor variations across the more than 2,000 members of the species.
Adult Pulex irritans are reddish-brown and the largest females can be one and half times the size of the smaller males. Also, the abdomen and thorax of the human flea are larger than the head which is much smaller in proportion to its overall body size. As you probably already know, the mouth structures of human fleas are incredibly efficient at puncturing the skin and sucking the blood out of its host.
Human fleas, like all other species, have three pairs of legs. Information gleaned from one of the University of Michigan websites says:
Pulex irritans has three pairs of legs used primarily for walking or running, but has extensive jumping abilities for escaping or getting onto a host. The enlarged coxae contain a highly elastic protein named resilin which is the primary reason for this ability. To jump, the flea will first lock their coxae back, compressing the resilin bands. The jump begins when the tergo-trochanteral depressor muscle relaxes, releasing the coxae. The resilin rapidly expands and causes the flea to summersault through the air at approximately 200 times gravitational acceleration. Jumping fleas can move more than 30 cm in about 0.02 seconds. The pretarsal claws on the middle or hind legs catch onto the host or substrate. Jumps can be made in rapid succession. Oriental rat fleas have been known to make up to 600 jumps per hour for 72 hours straight.
Mating & Reproduction in Human Fleas
Male flea genitalia is called the aedeagus. Females store the male’s sperm in a body structure called the spermatheca. Females lay eggs that are oval in shape and milky white in color. When the eggs hatch, flea larvae emerge in the form of maggots lacking eyes and legs. Yum!
The gestation period of the human fleas is 4 to 6 days, but scientists are not exactly sure if they breed year round nor do they know how long the time gaps are between breedings, if any. Once the flea lays the eggs there is no parental involvement with the only contribution to the development of the fleas being the adult excrement used to feed on.
Human fleas require blood meals to reproduce and will feed on just about any mammal, but domesticated dogs and pigs are their most common hosts.
Although they are originally thought to have been native to Central and South America, they now inhabit the entire globe except for the Arctic.