Life History

The cat flea is a cosmopolitan, eclectic species, having been recorded from more than three dozen species, including opossums, raccoons, kangaroos, and even birds. This wide host range explains this flea's ability to repopulate domestic animals after suppression efforts. Because it lacks host specificity and tends to feed on humans, the cat flea is a pest of both companion animals and humans with whom they share their abode.

FIGURE 1 Cat flea life cycle: adult (top), eggs, larva, and cocoon (enclosing pupa). (Illustration by Cara J. Mitten.)


Once adult cat fleas locate a host, they tend to remain on that animal unless dislodged. They feed readily and mate on the host. Female fleas lay eggs while on the host and because the eggs are not sticky, they readily fall off into the host's environment, with large numbers accumulating in areas frequented by the animal. Each female flea can produce more than two dozen eggs per day. Adult fleas are about 1 to 4 mm in length and are strongly flattened from side to side. They are equipped with relatively long legs armed with strong outwardly projecting spines. Cat fleas have a collar of spines (ctenidium) on the back and another row of spines above the mouth. These characteristics allow for rapid movement through the host's hairs and also serve to resist removal from the fur.

Once the adult flea finds a host, it begins to feed. Typically the female mates and begins oviposition within a couple of days. On the host, a female flea averages about one egg per hour and, as a female flea can live on the host for several weeks, potential production can amount to hundreds of eggs in her lifetime. Only the adult stage is parasitic; all other life stages develop off the host (Fig. 1). Eggs

Cat flea eggs are approximately 1 mm in length, with little surface structure other than aeropyles (permitting gaseous exchange for the developing embryo) and micropyles (for sperm entrance during fertilization). Typically, the larvae hatch within 24 to 48 h after oviposition, with more rapid hatching at warm temperatures.


From the eggs emerge small, white, eyeless, legless larvae with chewing mouthparts. Because they seldom travel far from where they hatch, cat flea larvae are usually found in furniture, carpeting, or outside in areas frequented by flea hosts. Flea larvae have three instars that, under favorable conditions, can be completed in as little as 10 days. Larvae will develop only in protected microhabitats in which the relative humidity exceeds 75%. Cool temperatures, food shortages, or other unsuitable environmental conditions may extend larval developmental time to several weeks or a month. The third instar voids its gut approximately 24 h before initiation of cocoon construction. The white prepupa wanders until it locates an appropriate site for pupation and then begins to spin a silk cocoon. Frequently, environmental debris is incorporated into the cocoon, adhering to the sticky silk fibers, so that the cocoon may appear as a small dirt clod or lint ball.


Within its cocoon, the prepupa molts to the pupa and continues metamorphosis to the adult flea within about 4 days, under favorable conditions. Length of the preemerged adult stadium is the most variable in the flea life cycle, ranging from less than a day to several months (or perhaps over a year). The mechanisms are not completely understood, but it appears that some individuals are programmed to delay emergence. Likely this is an evolutionary strategy whereby offspring emerge over an extended interval, ensuring that some successfully achieve hosts. Stimuli such as pressure, carbon dioxide, and warmth (triggers associated with mammalian hosts) serve as releasers, causing the adult flea to emerge from the cocoon. Upon emergence, if the flea does not locate a host immediately, it can survive for approximately 7 to 10 days (or longer under high-humidity and low-temperature conditions).

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