ORDER SIPHONAPTERA (APHANIPTERA) : FLEAS 191 



less distinctly divided into nine rings. There are some 

 definitely placed bristles on the head, the number and exact 

 position of which are useful for discriminating species. 



The most conspicuous appendages of the mouth are the 

 maxillae and their palps, which more or less conceal the 

 other parts. The maxillae are, commonly, triangular 

 dependent flaps, and their stout segmented palps project 

 like antennae from the lower front of the head. Between the 

 maxillary flaps are to be found the labial palps ; these spring 

 from an insignificant labial plate, are more or less segmented, 

 and form by their apposition, a sheath for the piercing and 

 suctorial tube. This last consists of (i) a pair of longitudinally 

 grooved, finely serrated, needle-like mandibles, which by 

 their apposition form an efferent tube for the passage of 

 saliva ; and (2) an unpaired bristle — the epipharynx — which 

 by apposition with the mandibles, forms an afferent tube up 

 which the blood of the victim is sucked. 



The 3 segments of the thorax are quite independent. 

 Each consists of a dorsal arc (tergum or notum) carrying one 

 or more belts of bristles, and of two latero-ventral pieces 

 ("sterna"). In some species the pronotum, or tergum of 

 the 1st thoracic segment, has a comb of elegant teeth on its 

 after edge. 



The legs are composed of the usual segments, the number 

 of tarsal segments being 5. All three pairs of legs are long 

 and strong, the third pair being the longest. The legs are 

 remarkable for the great length and breadth of the coxa ; 

 the femur also, and to a less extent the tibia, are usually 

 much expanded. The number and disposition of the bristles 

 of the several joints of the legs are used for distinguishing 

 species. The paired claws are very strong, and have the 

 heel extremely prominent. 



The. abdomen, which is large and deep, is composed of 

 10 segments, of which not more than 9 are plainly apparent. 

 The first 7 are unmodified rings, consisting each of a tergal 

 and sternal arc, bearing one or more belts of bristles ; the 

 last 3 are modified — differently in the two sexes — for sexual 

 purposes. The 8th segment is much dilated ventrally, more 

 so in the female. In the 9th segment the tergum is in great 

 part occupied, dorsally, by a pitted and setose sensory plate 



