Ctenocephalides felis The large tooth-like structures on the head of the cat flea help it hang onto the host’s hair and keep it from being dislodged by scratching or shaking.
The 2,500 or so species of fleas are ectoparasites, living externally on mammals. These wingless insects depend on their hosts for mobility and dispersal. Unique leg adaptations allow a flea to leap onto its host, and its flattened body lets it move easily and quickly through mats of hair. Humans become ancillary hosts when domestic animals and pets are infested. Fleas can transmit deadly bacterial diseases to humans, including bubonic plague and murine typhus (from rat fleas) and cat scratch disease (from cat fleas). Skin irritation from flea bites is the immune response caused by the proteins in flea saliva.
Fleas are not strictly host specific, but prefer to stay in the nest or burrow of their chosen mammal. Larvae are not blood feeders, but feed on the debris, shed hair or feces of the host. Because fleas live closely with their hosts, they do not use elaborate mechanisms to find the host— they are attracted by movement and carbon dioxide. Adult fleas depend solely on blood for nutrition. Females use additional feedings for their eggs and can produce hundreds to several thousand eggs in a lifetime.