ORDER DIPTBRA 123 



mouth-part en ;it /■'. In a Jaj it grow 



its skin, which bursts and peels off; this 



a day later. The maggot thus sheds its skin twii . 



consequently there are three larval 



- three or four da 



When aboat to transform into a pupa or chrysalis, the 

 body contracts into a barrel-shaped form, as Been in i 

 L42, /> : its Bkin turns In-own and hard, forming a 

 (called puparium) within which the larva changes to a 

 chrysalis. Remaining in this stage for about a week (five 

 to seven days), the fly is formed, and, pushing off one end 

 of its pupa-case, walks nervously about, until its soft, K 

 wings expand and become dry. when it takes to flight. It 

 thus lives a fortnight before acquiring wings, and, as a fly, 

 may live a few weeks, perhaps until frost; but in a 



- may pass the winter within the house, or in pi 

 places outside, and appear < at of doors in the spring. 



There are probably 10,1 Ler <d Diptera 



in the [Jnited States alone, hut to a large proportioi 

 them the preceding description will in general apply. 

 Hence, by studying thoroughly one fly, we can obtain a 

 I idea of the general structure of all. 



In certain flies (Blepharoceridae) there are two kind- 

 females one kind with mouth-parts adapted for piercing 

 the -kin of animals ami sucking their blood, and the other 

 with mouth-parts like those of the male, the maxilla' being 

 :it. In the females of other flies which suck . the 



males feed on honey. 



In the flies, whose mouth-parts vary astonishingly in 

 structure, bo that some are piercers and md others 



suckers and tappers, there is also a great variety of la 

 form-, different modes of metamorphos quently 



great powers of adaptation to different stations in A 



few species live in the sea. many in fresh many, 



as the Tachina, are parasites in the bod i - terpillars 



ami other insects. There is everywhere a rful liar- 



