4 Fleas of Eastern United States 



a dorsal tergite and a ventral sternite. The seventh tergite 

 usually bears one or more stout bristles on each side, the an- 

 tepygidial bristles, which are of great systematic importance 

 because of their variablity in the different groups. 



The genitalia of both sexes are of tremendous taxonomic im- 

 portance. In the male they have evolved in part from the ninth 

 abdominal segment, the tergite forming the clasper. Each 

 clasper (there is one on each side) consists of a broad plate 

 which ventrally is prolonged to form a manubrium and dorsally 

 bears a conelike protuberance known as the process of the 

 clasper. Articulated to the clasper on each side of the body is 

 a movable process called the movable finger (exopodite, ac- 

 cording to some authors) whose shape and size are very sig- 

 nificant. Sometimes both processes are movable, but in most 

 instances the arrangement is as described, with only one process 

 capable of movement. The ninth sternite, which forms the lower 

 clasper, has the shape of a boomerang since it consists of an 

 anterior or vertical arm and a posterior or horizontal arm (also 

 called the ventral arm) . The penis is long and bladelike and 

 bears posteriorly a paramere which in certain groups is very 

 significant in classification. Below the penis is the spring which 

 may be long or short and, if long, is frequently coiled distally. 

 In the female the shape of the seventh sternite is of great im- 

 portance, particularly if its posterior margins are sinuate or en- 

 tire. The form of the heavily sclerotized receptaculum seminis, 

 consisting of a head and tail, is also of great significance. 



For illustrations of the structural terms discussed above, see 

 Plate I. 



LIFE HISTORY AND CONTROL 



Fleas undergo complete metamorphosis involving four dis- 

 tinct stages — egg, larval, pupal, and adult. The eggs, larvae, 

 and pupae are residents of the nest of the host and not parasitic, 

 according to most authors; the adults, however, feed exclusively 

 on blood. The eggs are laid by the adult female either in the 

 nest of the host or among its hairs or feathers without any ag- 

 glutinating material to keep them attached; hence, they are 

 easily shaken off into places where the host sleeps or rests. 



The rate of development of the cream-colored, oval eggs 

 varies among the different species and also depends in a large 

 measure on temperature and humidity. When the eggs hatch 

 they give rise to white or yellowish larvae which are cylindri- 

 cal in shape and very slender. The larvae are very active, 



