Fleas are laterally compressed and Wingless insects. Their mouthparts are piercing-sucking which enables them to suck blood from a host animal.
Adult fleas are parasites of warm-blooded vertebrates. The majority of species occur on mammals, but about 100 species are found on birds. Fleas have complete metamorphosis, with distinct egg, larva, pupa, and adult stages. Adult fleas remain on the body of the host and suck blood about once per hour, so they seldom leave the host animal. If they do, they quickly jump back to the host. Eggs are laid on the host, but fall to the ground. Larval stages feed and develop on the ground or bed of the host animal (or indoor carpeting); they have chewing mouthparts and resemble fly maggots.
When development is complete, the larvae often will move to a location different from the larval feeding site and create a silk cocoon, which is usually covered with pieces of debris from the substrate. The pupa forms inside the cocoon, and the flea emerges as an adult by breaking open the cocoon and crawling to the surface.
Lice are parasites of mammals or birds. Sucking lice live on the skin of mammals, and all stages suck the blood of their hosts. These insects are host specific and do not infest animals other than their primary host: the dog louse remains a pest of dogs and the human louse remains a pest of humans. The louse stays on its host throughout its life cycle;
and lice almost always are transmitted by contact. Humans are hosts of head lice and pubic, or crab, lice.
The shape of the louse’s claws influences its ability to infest different races of people. In the U.S., head lice infestations are 35 times higher among Caucasians than among Blacks. Contributing to this difference is the ability of the claws to grasp the hair type. Caucasian hair is round whereas Afro-Caribbean hair is flattened oval. The claws of head lice and body lice may have difficulty grasping the hair of non-Caucasians.
Silverfish have flat bodies that give them access to cracks and crevices in kitchens and bathrooms, and wall voids throughout houses and commercial buildings. They are active at night and move quickly in and out of harborages, which makes infestation sites difficult to find and treat. Sticky traps can be useful in locating infested harborages, so liquid and dust applications can be more effective. Silverfish often are found in sinks and bathtubs, because they cannot climb smooth, vertical surfaces.
Psocids are common household pests; they usually occur in kitchens and bathrooms, but can be found in other humid locations. In commercial buildings, they can occur in rooms where books and files are stored. There are several psocid species that infest stored grain products, especially if the product is exposed to moisture. Inspection for these small insects is difficult without the aid of a hand lens.