The dog flea, Pulex serraticeps, is easily distinguished from the flea of man by the large thick bristles on the posterior margin of the first thoracic ring (fig. 384).
Genus. Xenopsylla, Glink.
Xenopsylla cheopis, Rothschild.
This is the common rat flea of tropical countries. Rothschild[377] says: “Although practically cosmopolitan, it cannot apparently flourish in temperate and cold climates.”
In the male the bristles of the flap-like process of the clasper all slender; in the female the narrow portion of the receptaculum seminis long. Originally discovered in Egypt.
This is apparently the chief plague flea. The Indian Plague Committee have proved that this flea is easily infected when fed on plague rats, and that the bacillus multiplies rapidly in the flea’s stomach and that the fleas may remain infective for fifteen days. How the flea infects man does not apparently seem to have been proved, as it does not do so through its bite, but the excrement is highly infective. It is probable that this poisoned fæcal matter gets to the wound caused by the piercing mouth.
Xenopsylla brasiliensis, Baker,
occurs on rats in West Africa and has been introduced into Brazil.
Genus. Ctenocephalus, Kolen.