Siphonaptera, or Fleas 123 



Mitzmain (1910) has described in detail the act of biting on man, 

 as observed in the squirrel flea, Ceratophyllus acutus. "The flea 

 when permitted to walk freely on the arm selects a suitable hairy 

 space where it ceases abruptly in its locomotion, takes a firm hold 

 with the tarsi, projects its proboscis, and prepares to puncture the 

 skin. A puncture is drilled by the pricking epipharynx, the saw- 

 tooth mandibles supplementing the movement by lacerating the 

 cavity formed. The two organs of the rostrum work alternately, 

 the middle piece boring, while the two lateral elements execute a 

 sawing movement. The mandibles, owing to their basal attach- 

 ments, are, as is expressed by the advisory committee on plague 

 investigations in India (Journal of Hygiene, vol. 6, No. 4, p. 499), 

 ' capable of independent action, sliding up and down but maintaining 

 their relative positions and preserving the lumen of the aspiratory 

 channel.' The labium doubles back, the V-shaped groove of this 

 organ guiding the mandibles on either side." 



" The action of the proboscis is executed with a forward movement 

 of the head and a lateral and downward thrust of the entire body. 

 As the mouth-parts are sharply inserted, the abdomen rises simultane- 

 ously. The hind and middle legs are elevated, resembling oars. 

 The forelegs are doubled under the thorax, the tibia and tarsi resting 

 firmly on the epidermis serve as a support for the body during the 

 feeding. The maxillary palpi are retracted beneath the head and 

 thorax. The labium continues 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 maxillag 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 move- 

 ment of the abdomen. The swinging of the abdomen gradually 

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

 gradually becomes duller and less sensitive as feeding progresses. 

 The movements of the elevated abdomen grow noticeably feebler 

 as the downward thrusts of the springy bow-like labium becomes less 

 frequent." 



"As the feeding process advances one can discern through the 

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

 from the pharynx, accompanied by a peristaltic movement. The 



