Life Cycles

The life cycles of all fleas are basically the same. They consist of six stages -   egg, 3 larval stages, pupa and adult (male or female). The general cycle is illustrated here using the specific life cycle of  Ctenocephalides, which contains the two species (C. canis and C. felis) of importance  in dogs and cats.

Adults are the only flea stages spending most of their time on a host. They  leave the host  occasionally and usually only when one host makes contact with another. All other flea stages - eggs, larvae and pupae - are found in the immediate environment of the host. In dogs and cats this would primarily include places in the home and kennel used for resting and sleeping. Therefore by far the greatest majority of fleas are found concentrated in the host's environment as eggs, larvae, pupae and newly emergent adults and only a small proportion of the total flea population is found on a host as feeding,   reproducing adults plus newly laid eggs and hatched larvae that have not dropped off.

Adult Ctenocephalides lay eggs on their hosts. These are approximateley 0.5mm long and white in color. At optimal conditions of temperature and humidity, first stage larvae will hatch about four days later. A mixture of eggs, L1s and adult flea feces drop off the host into the environment where most of the cycle develops. Larvae feed on feces from adult stages and this largely consists of dried host blood and tissue ingested by these feeding adults. Larval stages molt twice and will reach the third stage (L3) in two weeks when their environment is warm and moist. L3s which are about 5mm long now spin a cocoon and inside each pupal case transform (metamorphose) into an adult.

Adults emerge from the pupa and seek a host to feed and reproduce. Females will lay eggs within 48 hours of feeding on their new host

Under optimal conditions of a warm, moist environment the whole flea life cycle may be completed in three weeks.

Temperature and moisture are the primary factors  controlling the flea life cycle.   Studies have shown that the Ctenocephalides life cycle stages  will develop within a range of temperatures from 13'C to 32'C and a range of relative humidity from 50% to 92%. The life cycle will be completed in 2 to 3 weeks at the high ends of these ranges and may take as long as 3-4 months at the low ends.

Temperatures greater than 35'C will kill developing larvae and pupae.

Adult fleas may survive from 2 to 6 months in the absence of a host for feeding. However,  when hosts are present, adult fleas will spend the majority of their time feeding and reproducing on their hosts. 

Adults fleas are fairly long-lived. Most will live up to one year and some can live as long as two years under natural conditions if they are unthreatened by chemical control products.


Parasites and Parasitic Diseases of Domestic Animals
Dr. Colin Johnstone (principal author)
Copyright 1998 University of Pennsylvania
This page was last modified on January 24, 2000