CHAPTER XXXII 

 THE SIPHONAPTERA 



The Siphonaptera or Fleas are curious, small insects ranging from 

 about a twentieth to a sixth of an inch long. They are evidently related 

 to the flies in many ways but are much modified. Most of the members 

 of the group have their bodies laterally compressed so that they are 

 narrow (Fig. 353). The head is not sharply separated from the body and 

 the antennae are short and stout. The mouth parts are for piercing 

 and sucking, and modified in a different way from those of other insects 

 which feed in this manner. While the identity of the various parts has 



Fio. 353. Adult Cat and Dog Flea (Ctenocephalus canis Curtis), greatly enlarged. 



(Original.) 



not been conclusively proven, it seems probable that a long median 

 pricking structure is the labrum or else the hypopharynx; a pair of 

 similar structures are the mandibles; a pair of rather short, stout struc- 

 tures at the sides, each with a palpus, are the maxillae, and that the 

 labium is represented by a rather stout basal portion bearing two long 

 segmented pieces, perhaps the palpi, so shaped as together to form a 

 loose sheath for the piercing parts. Compound eyes appear to be 

 absent. 



Backward-projecting spines occur on the body, largely at least, 

 preventing backward movements between the hairs on the body of the 



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