Human Flea

*Pulex irritans*, the human flea, is a combless flea 1.5–4 mm long, reddish-brown and laterally flattened, with a rounded head and a single row of bristles behind the eye. Despite the name it is not restricted to people — pigs, dogs, badgers, foxes, coyotes and other carnivores are common hosts, and modern infestations in developed countries usually trace to livestock, wildlife dens, or crawl-space denning animals rather than to human bedding. Females lay eggs loosely in host resting material; the egg–larva–pupa–adult cycle takes three to six weeks depending on temperature and humidity, and adults are long-lived and tolerate starvation well.

Adults feed on whatever warm-blooded host is available and will move to people readily when the primary host is gone. Bites appear as itchy erythematous papules, often in irregular clusters on legs and waistline where clothing constricts. The species is a recorded secondary vector of *Yersinia pestis* in some sylvatic plague foci and a documented intermediate host of *Dipylidium caninum*. Larvae are free-living in floor debris, straw, and soil, feeding on organic matter and adult flea faeces, and are strongly negatively phototactic.