© Stuart M Bennett 2003
Ctenocephalides felis
(The Cat Flea)


Cat and dog fleas are very similar in appearance and both species can live on both cats and dogs.  Humans are mainly attacked by cat fleas.  A cat or dog may have a light infestation of fleas without the human inhabitants knowing it, but if the pets are carrying large numbers of fleas, then there is naturally a greater likelihood of humans being bitten.  A heavy infestation may occur if the cat or dog is removed from the house, for then the insect has no alternative but to feed off us.  In such cases one may comfort oneself with the fact that the cat and dog fleas cannot breed without their principle hosts, and so eventually the infestation will die out on its own.  On the other hand, they can live for months on a diet of human blood, so it needs an unusual amount of patience to wait until the fleas die of old age. 

The Cat Flea; (Ctenocephalides felis) & The Dog Flea (Ctenocephalides canis)

These two fleas, particularly the former, are the most common species found in and around homes. They are most abundant in summer, and seem to be especially numerous when homes are re-occupied afteer the residents have been away for a few weeks. The cat and dog flea are so similar in appearance and bilology that for practical purposes they can be described under the same heading.

Description: The female is 2.5 mm long, and the male is slightly smaller. The head of the female cat flea is twice as long as high when seen from the side, while that of the female dog flea as less than twice as long as high. In both species, the genal comb consists of 8 pairs of spines, and the pronotal comb also consists of 8 pairs (click here to see diagram). With the aid of low magnification, it can be determined that the first 2 anterior spines of the genal comb of the cat flea are about equal in length, while the first spine is distinctly shorter in the dog flea (Ewing and Fox, 1943; Pratt and Wiseman, 1962).

The larvae of both species are nearly twice as long as the adults. They feed on particles of dry blood, excrement, and various organic substances collected in corners and crevices in the infested premises. When infestations are very heavy, the accumulations of grayish larvae and white eggs give the sleeping quarters of cats and dogs a "salt-and-pepper" appearance that easily identifies the infestation.


                                             Flea Eggs                                                                  Flea Larvae

Flea Cocoon

How Infestations Are Spread: Particularly in warm, humid areas, the exclusion of cats and dogs, or their proper management, is necessary to prevent flea infestations. Residential premises are sometimes so heavily infested that cats will leave to seek relief, and will carry the infestation to an uninfested home. If an infested stray cat has kittens under or near an uninfested home, the appearance of fleas within the house is very likely to follow. Fleas often also become established in the lawns of heavily infested residences, in warmer areas of the country. Fleas can jump vertically for 5 or 6 inches (about 15 cm), and can attach themselves to skin or clothing. Some pest control operators avoid being bitten by spraying insecticide onto their clothing, but this is not according to label instructions.

In addition to cats, dogs, and humans, many animals are attacked by cat fleas and dog fleas.

Thanks are due to Walter Ebeling for some of these notes
University of California
Division of Agricultural Sciences ©1975, 1996, 2002

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