162 THE LIFE OF AN INSECT. 



It will be readily imagined that those larvae 

 which dwell in the water must be furnished some- 

 what differently, in order to enable them to 

 breathe. And here, as we shall now find, there 

 are some very curious arrangements, in order to 

 effect this object. They may be considered under 

 two divisions. First, contrivances for breathing 

 air while the larva is immersed in the water; 

 and, second, apparatus for extracting the dissolved 

 oxygen gas necessary for breathing from the 

 water. 



Let us select a few of the most singular in- 

 stances under the first of these divisions. "No 

 better example," write the entertaining authors of 

 the Introduction to Entomology, " can be selected 

 than the gnat. You must have occasionally ob- 

 served in tubs of rain-water, numerous little wrig- 

 gling worm-like animals, which frequently ascend 

 to the surface, there remain awhile, and then bend- 

 ing their head under the body, rapidly sink again 

 to the bottom. These are the larvae of some 

 species of the genus just named ; and if you take 

 one out of the water and examine it, you will 

 perceive that it is furnished, near the end of the 

 body, with a singular organ, which varies in length 



