444 THE COMMON GNAT. 



formed into perfect Gnats. The chrysalids swell 

 at the head, and the flies burst from their inclosure. 

 If at the instant ot the change a breeze springs up, 

 it proves to them a dreadful hurricane, as the water 

 gets into their case, from which they are not yet 

 perfectly loosened • tVfis immediately sinks, and 

 they are drowned*. 



The female deposits her eggs on the surface of 

 the water, and surrounds them with a kind of unc- 

 tuous matter, which prevents them from sinking ; 

 and she at the same time fastens them with a thread 

 to the bottom, to prevent them from floating away, 

 at the mercy of every breeze, from a place the 

 warmth of which is proper for their production, to 

 any other where the water may be too cold, or the 

 animals, their enemies, too numerous. In this state 

 they therefore resemble a buoy that is fixed by an 

 anchor. As they come to maturity they sink deeper ; 

 and at last, when they leave the egg t they creep in 

 the form of grubs at the bottom. 



If the Gnats were not devoured by fish, water- 

 fowl, swallows, and other animals, the air would 

 often, from their immense multitudes, become 

 darkened : a few instances have occurred in which 

 this has been the case. In July, August, and Sep- 

 tember 1776, at Oxford, they were sometimes seen 

 towards the evenings in such myriads as literally to 

 darken the rays of the sun ; and their repeated bites 

 often swelled the exposed parts of the body to an 

 enormous size, and caused the most troublesome 



* Barbut's Gen, Insect. 306. 



