CLASS HEXAPODA. 75 



of fleshy disks, from the viscid secretion of which the 

 animals are enabled to crawl on smooth surfaces, often 

 overhead with their body inverted. 



ORDER APHANIPTERA (af a nlp'te ra). 



The Fleas, which differ from the Dipterous insects in 

 having the body laterally compressed, and the wings ru- 

 dimentary, belong to this order. FIG 12g 

 Fleas are parasitic on many do- 

 mestic animals. The eggs find 

 their way, from the hair of the 

 hosts, to the dust in the cracks 

 of floors, where the larvae, which 



are provided for a time With Pu'lex Ir'.ri tans. Human Flea. 



jaws, feed on refuse. They then 



undergo a transformation, finally appearing as adults. 

 The jumping power of the Flea is proverbial, the animal 

 being said to be able to clear a distance of two hundred 

 times its own length. 



ORDER LEPIDOPTERA (lep i dop'te ra). 



This order includes those insects which have all four 

 wings covered with imbricate (overlapping each other) 

 scales ; the maxillse greatly elongated and placed side by 

 side, forming a tube, which, when not in use, is coiled 

 into a spiral ; and the jaws, so characteristic in the 

 Beetles, obsolete. The series of transformations is per- 

 fect. The larva, Caterpillar' on hatching from the egg, 

 is provided with not only the full complement of thoracic 

 limbs, but there are often from one to five pairs of, so- 

 called, pro-leys, fleshy outgrowths along the abdomen. 

 While in this stage, the salivary glands often secrete a 



