[435] SCIENTIFIC MANUAL. 149 



In this order are found insects both beneficial and inju- 

 rious to the interests of man. Among them we find leaf- 

 eaters, pine-borers and gall-flies that are injurious ; while 

 on the other hand, there are the ichneumon, flies, ants and 

 wasps, which prey upon other insects, and the useful little 

 bee, which labors so persistently in laying up his stores, 

 which are appropriated by man to his own use. The bees 

 and other insects also serve the important purpose of fer- 

 tilizing the flowers of plants, by carrying the pollen from 

 blossom to blossom, in their search for honey. 



7. "DiPTERA." {Mosquitoes, gnats, flies, etc}. Insects with a 

 horny or fleshy proboscis, two wings only, and two knobbed 

 threads, called balances or poiser, behind the wings. Trans- 

 formation complete. The larvae are maggots, without feet, 

 and with the breathing holes generally in the hinder ex- 

 tremity of the body. Pupae mostly incased in the dried 

 skin of the larvae, sometimes, however, naked, in which 

 case the wings and legs are visible, and are found to be 

 more or less free or unconfined." In this order are sever- 

 al species which are extremely annoying to man in sum- 

 mer, such as mosquitoes, gnats, and various kinds of flies, 

 including the house fly, blow- flies, flesh-flies, and the cheese 

 fly, which produces skippers. 



Among those injurious to vegetation we find the Hes* 

 sian fly, so destructive in its larva state to wheat. There are 

 still others, which have no common name, which deposit 

 their eggs among plant lice or in the nests of other insects, 

 where they either destroy the young, or subsist upon the 

 food stored up for the use of the young when hatched, 

 and thus starve them to death. 



These seven orders embrace with sufficient accuracy 

 those insects which from their injury or benefit to man, re- 

 quire the attention of agriculturists. 



The limit to which this work is necessarily circumscribed, 

 forbids the enumeration of the subdivisions of these orders, 

 or detailed descriptions of individual varieties. 



