. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 418 FLEAS It is said to be very annoying to man also. The common squir- rel flea in North America, C. acutus, is found on a number of species of wild rodents, and also occasionally on rats and mice. It does not attack man so readily as does C. fasdatus, but is nevertheless not averse to human' blood. This species has come into great importance in California as the transmitter of plague from rats to ground squirrels. It is probable, how- ever, that other species of this genus and of allied genera may qui
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. 418 FLEAS It is said to be very annoying to man also. The common squir- rel flea in North America, C. acutus, is found on a number of species of wild rodents, and also occasionally on rats and mice. It does not attack man so readily as does C. fasdatus, but is nevertheless not averse to human' blood. This species has come into great importance in California as the transmitter of plague from rats to ground squirrels. It is probable, how- ever, that other species of this genus and of allied genera may quite as readily transmit plague, depending only on the extent to which their habits bring them in contact with infected animals. Chiggers. — The chigger, chigoe, jigger or sand flea, Derma- tophilus (or Rhynchoprion) penetrans (Fig. 183), as it is vari- ously called, is one of the most de- spised pests of tropical countries. It is a very small flea of the family Sarcopsyllidae, about one mm. in length, with no combUke spines and relatively slender legs. It has a very comical pointed forehead, like a helmet worn with the .point forward. The males and virgin females of this species are similar n::''D^at:^'Z<^^ *« ^^^^^ ^^^^ ^^ .^^-^Its, except that impregated female. X 30. (After they attack a wide range of hosts. Karsten from Riley and Johannsen.) ^^^ j^ ^^^ principal host of this particular species, but pigs are also very commonly attacked. Chiggers occur especially in sandy regions where there is much underbrush, and here they lie in ambush on the vegetation, dead leaves or sandy soil, ready to attack any host which may come their way. The particular importance of this flea lies in the fact that the impregnated females have the aggravating habit of burrowing into the skin especially in such tender spots as under the toe nails, where, nourished by the blood of the host, the eggs develop and cause the abdomen to swell into a great round ball as large as a pea, leaving the he
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