CHAPTER XXVI 

 ORDER SIPHONAPTERA * 



The Fleas 



The members of this order are small, wingless insects, in which the body 

 is laterally compressed, so that the transverse diameter is small, the vertical 

 one great. The month-parts are formed for piercing and sucking. The 

 metamorphosis is complete. 



These tiny tormentors are best known to us in the adult state; for 

 it is only the adults that annoy us and our household pets. The larvas 

 and pupae are rarely observed except by students who search for them. 



The body of the adult is oval and 

 greatly compressed, which allows the 

 insect to glide through the narrow 

 spaces between the hairs of its host. 

 The integument is smooth, quite hard, 

 and armed with bristles, which are 

 arranged with great regularity (Fig. 

 569) and thus afford good characters 

 for distinguishing the different species. 

 The smoothness and firmness of the ^^ *** 



The dog-flea and its 



Fig. 570. — Head of a flea, Ceralophyllus 

 multispinosus: f, falax; mx, maxilla; mx.p, 

 maxillary palpi; p, proboscis. (After Baker.) 



body make it easy for the insect to escape when caught between the 

 fingers of man or the teeth of lower animals. When once out of the 

 clutch of an enemy it quickly leaps away. 



The head is broadly joined to the thorax. There are no compound 

 eyes; but on each side of the head there is usually an unfaceted eye; 

 these, however, are sometimes wanting. Each antenna lies in a groove 

 somewhat behind and above the eye (Fig. 570). The antennas are three- 

 segmented; the third segment, which is called the flagellum, may also 

 be divided into several divisions or false-segments. The legs of fleas are 

 long, strong, and fitted for leaping. 



* Siphonaptera: siphon (trL^uv) a tube; apteros (airrcpos) without wings. 



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