1910] California Rodent Fleas 79 



abdomen rises simultaneously^ The head and middle legs are 

 elevated resembling oars. The fore legs are doubled under the 

 thorax, the tibia and tarsi resting firmly on the epidermis serve 

 as a support for the body during feeding. The maxillary palpi 

 are retracted beneath the head and thorax. The labium con- 

 tinues to bend, at first acting as a sheath for the sawing mandibles, 

 and as these are more deeply inserted, it bends beneath the head 

 with the elasticity of a bow, forcing the mandibles into the 

 wound until the maxillae are embedded in the skin of the victim. 

 When the proboscis is fully inserted, the abdomen ceases for a 

 time its lateral swinging. 



The acute pain of biting is first felt when the mandibles have 

 not quite penetrated and subsequently, during each distinct 

 movement of the abdomen. The swinging of the abdomen 

 gradually ceases as it becomes filled with blood. The sting of the 

 biting becomes gradually duller and less sensitive as feeding 

 progresses. The movements of the elevated abdomen grow 

 noticeably feebler as the downw^ard thrusts of the springy bow- 

 like labium become less frequent. 



As the feeding process advances, one can discern through 

 the translucent walls of the abdomen, a constant flow of blood, 

 cau dally from the pharynx, accompanied by a peristaltic move- 

 ment. 



The end of the meal is signified in an abrupt manner. The 

 flea shakes its entire body, gradually withdraws its proboscis by 

 lowering the abdomen and legs, and violentl}^ twisting the head. 

 When starved for several days, the feeding of the rat fleas is 

 conducted in a rather vigorous manner. As soon as the proboscis 

 is buried to full length, the abdomen is raised and there ensues a 

 gradual lateral swaying motion, increasing the altitude of the 

 raised end of the abdomen until it assumes the perpendicular. 

 The flea is observed at this point to gain a better foothold by 

 advancing the fore tarsi, and, then gradually doubling back the 

 abdomen, it turns a back spring, with extreme agility, nearly 

 touching with its dorsal side the skin of the hand upon which it 

 is feeding. Meanwhile, the hungry parasite feeds ravenously. 



It is interesting to note the peculiar nervous action which the 

 rodent fleas exhibit immediately when the feeding process is 

 completed, or when disturbed during the biting. Even while 

 the rostrum is inserted to the fullest, the parasite shakes its head 

 spasmodically, in a twinkling the mouth is withdrawn and the 

 flea hops away. 



