“Osbrink and Rust (1985) reported that there was no significant difference in the mean number of fleas collected from any particular area of the cat.”
Ref. Osbrink, W.L.A., and M. K. Rust. 1985. Seasonal abundance of adult cat fleas, Ctenocephalides felis (Siphonaptera: Pulicidae) on domestic cats in southern California. Bull Soc Vector Ecol. 1985, 10, 30-5 *
This finding is disputed by Meng-Hao Hsu, Tung-Ching Hsu and Wen-Jer Wu at the Department of Entomology, National Taiwan University. 
“A significantly higher mean number of fleas was found on the area of head plus neck than on the ventral part of the body. More specifically, the mean number of fleas was highest on both of the neck and dorsal areas. However, in terms of the density of fleas, the neck had more fleas than the dorsal area did. The fewest fleas were found infesting the legs and tail.”
See: Distribution of Cat Fleas (Siphonaptera: Pulicidae) on the Cat
Also of note: The 2008 Ig Nobel Biology Prize – which was awarded to Marie-Christine Cadiergues, Christel Joubert, and Michel Franc of Ecole Nationale Veterinaire de Toulouse, France for discovering that the fleas that live on a dog can jump higher than the fleas that live on a cat.
Further reading: The Flea Encyclopedia
* Sadly, the online-archive file for the The Bulletin of the Society of Vector Ecology, Volume 10, Issue 1, June 1985 , Osbrink and Rust, appears to be corrupted.