THE FLEAS OF NORTH AMERICA 



The sternum is ventral, and in lateral view usually appears to be 

 the smallest of the sclerites. It is the most heavily pigmented. In 

 nearly all genera it is without demarcation from the episternum, 

 but in some genera, such as Stenistomera and Cratynius, the meso- 



sternum is separated from the mesepisternum on each side by an 

 inner chitinous ridge, a character of generic importance. The mes- 

 episternum similarly may be separated from the mesepimeron by an 

 inner chitinous ridge (fig. 2), the pleural ridge, in many genera of 



