Cat Flea

The cat flea, *Ctenocephalides felis* (Siphonaptera: Pulicidae), is the flea encountered in well over 90% of residential and veterinary cases, on cats, dogs, and wildlife alike. Adults are 1.5–3.2 mm, wingless, laterally flattened, shiny reddish-brown, with both genal and pronotal combs and enormously developed hind femora for jumping. Development is complete metamorphosis: eggs, three larval instars, pupa in a silken cocoon, and adult. A blood-fed female lays 20–50 eggs per day, up to 2,000 in her lifetime; eggs are non-adhesive and fall from the host into carpet, bedding, and soil. At 27°C and 75% RH the whole cycle finishes in 17–26 days, but pre-emerged adults can remain quiescent in the cocoon for up to five months awaiting host cues.

Adults are permanent ectoparasites — once on a host they feed within minutes and rarely leave voluntarily, mating and defecating partially digested blood ('flea dirt') that drops off and feeds the larvae below. Emergence from the cocoon is triggered by vibration, warmth, and exhaled carbon dioxide, which is why a home vacant for weeks can produce a sudden mass of hungry fleas the day people return. Larvae are negatively phototactic and burrow deep into carpet pile and cracks, feeding on adult flea faeces and organic debris. Bites are typically clustered on ankles and lower legs, producing intensely pruritic papules, and the flea is the intermediate host of the tapeworm *Dipylidium caninum* and a vector of *Bartonella henselae* (cat scratch disease) and murine typhus.