TWO-WIiJGED INSECTS. 391 



There is no species of insects so troublesome to man as the 

 gnat. Others give occasional annoyance, like the wasp; but the 

 gnats thirst for human blood, and follow us in companies with the 

 most persevering constancy, till they have succeeded in satiating 

 their desires. In many marshy places in our country they swarm 

 in myriads. There, the legs and arms of individuals are swelled 

 to an enormous size, by the bitings of these voracious and insolent 

 insects. In many other countries they are much more troublesome 

 than in ours. 



There is something very singular in the trunk of the gnat, 

 or that instrument with which it is provided, and by which it 

 inflicts such pain on others, and obtains so much gratification for 

 itself. This instrument is a kind of sheath, which contains 

 several piercers. These issue, at the pleasure of the insect, from 

 a very narrow aperture. They are darted, in a moment, into the 

 flesh of the object on which it lights. Gnats are careful in the 

 choice of the particular place on the skin where they inflict the 

 wound. It will try several before it sends out its cruel piercers. 

 The place must have two properties : first, it must be easily 

 pierced ; and, secondly, there must be a vessel underneath con- 

 taining as much blood as it may have occasion to suck, to satisfy 

 its craving desires. 



The wings of a gnat are a very curious structure, and 

 worthy of attentive observation. By a close examination it is 

 found that these wings are covered with what seems at first a 

 beautifully-colored powder. By the help of the microscope, this 

 powder consists of regularly organized bodies resembling scales 

 and feathers. Though they are bestowed much more sparingly 

 than upon the butterfly, yet they are arranged with the utmost 

 regularity. 



The Gadfly has, from the most ancient times, been known 

 as the terror of the herd. At the sound of its approach, the 

 cattle are driven almost mad with terror. The young gadflies are 

 nourished under the skin, where they remain until they are fit to 

 pass into the pupa state, when they bury themselves in the ground, 

 and, after a few days spent under the earth, issue forth in their 

 perfect state. 



