120 NATURAL HISTORY OF AQUATIC INSECTS CH. 



escapes to the exterior of the body, and lodges be- 

 neath the thorax, where it collects into a good-sized 

 bubble ; this is probably useful in maintaining the 



B 



FIG. 34. Pupa of Corethra. A, ventral view ; B, side view. 



upright position. The fore air-sac breaks up, but the 

 hinder one remains, apparently not in a functional 

 condition. A pair of respiratory trumpets, somewhat 

 similar to those of the Gnat pupa, are now the chief 

 means of communication with the outer air. They 

 are narrowed at the extremity, and open by a very 

 contracted slit. 



The fly which issues from the pupa-skin is a small 

 Gnat-like Insect. The male has beautiful plumed 

 antennae. The female deposits on the surface of water 



