CHAPTER XII. 



THE APHANIPTERA. — THE STREPSIPTERA. 



The Aphaniptera are insects which are known to everybody ; but 

 the SU'cpsiptera have never been seen except by a few naturahsts. 

 The first are Fleas, and are admitted to be particularly interesting 

 insects, quite as much as regards their structures, their instincts, 

 and metamorphoses, as on account of their well-known habits. 

 The adult fleas are suckers, like the Heviiptera, but their mouths 

 are constructed very differently, for the lip is a sharp tissue ; the 

 mandibles are long flattened blades finely denticulated on their 

 margins ; the jaws are small triangular pieces ; and the lower lip 

 is a membranous lamina supporting large palpi. The eyes are 

 situated on the sides of the head, and appear to be simple ; the 

 antennae are very small, and the wings only exist in the form of 

 scales, as small vestiges of those important organs — hence the name 

 of ApJianiptcra. The legs are strong and spiny, and the hind ones, 

 which are longer than the others, have their thigh pieces enlarged, 

 and are admirably suited for jumping. These insects undergo 

 complete metamorphoses, and the larvae are worm-shaped, and the 

 nymphs are inactive, but the last transformation is imperfect, for 

 the organs of flight are rudimentary. There is only one family in 

 this order, and it has only one genus, that of the fleas {Pulex). 

 Each species attacks one animal in particular, and one kind selects 

 man as the object of its attentions. This last is readily recognised 

 by its smooth head, and by the stiff hairs upon the segments of 

 the thorax and the abdomen. 



It is not necessary to explain how fleas live; they multiply 

 prodigiously in hot climates, and grow to a very unusual size 

 under certain conditions. For instance, immense fleas, which are 



