CLASSIFICATION AND ORIGIN OF INSECTS 



gnats, on the contrary, have the limbs distinct and 

 inclosed in sheaths. They are generally inactive, but 

 some of the aquatic species continue to swim about. 



One group of flies, which is parasitic on horses, 

 sheep, bats, and other animals, has been called the 

 Pupipara, because it was supposed that they were 

 not born until they had arrived at the condition of 

 pupae. They come into the world in the form of 

 smooth, ovate bodies, much resembling ordinary dip- 

 terous pupae, but as Leuckart has shown, they are 

 true, though abnormal, larvae. 



The next order, that of the Aphaniptera, is very 

 small in number, containing only the different species 

 of flea. The larva is long, cylindrical, and legless; 

 the chrysalis is motionless, and the perfect insect is 

 too well known, at least as regards its habits, to need 

 any description. 



The Heteroptera, unlike the preceding orders of 

 insects, quit the egg in a form differing from that of 

 the perfect insect principally in the absence of wings, 

 which are gradually acquired. In their metamor- 

 phoses they resemble the Orthoptera, and are active 

 through life. The majority are dull in color, though 

 some few are very beautiful. The species constitut- 

 ing this group, though very numerous, are generally 

 small, and not so familiarly known to us as those of 

 the other large orders, with indeed one exception, the 

 well-known bug. This is not, apparently, an in- 

 digenous insect, but seems to have been introduced. 

 The word is indeed used by old writers, but either 

 as meaning a bugbear, or in a general sense, and not 

 with reference to this particular insect. In Britain 



