NATURAL HISTORY. 



157 



bodies, near the tail, through which they 

 breathe ; and that part must, you know, be at 

 the top to get air. Besides this, its tail and 

 its breathing tube both end in a sort of fun- 

 nel, made up of hairs placed somewhat in the 

 form of a star, and covered with oil, so as to 

 keep off water, and these buoy or float it up. 

 When it wishes to sink, it just folds up its 

 funnels, and shuts up in them a little bubble 

 of air, which it breathes under the water ; 

 arid when it wishes to rise, it opens its funnels, 

 and they float it to the top again. Here is a 

 drawing which will show it to you. 



Larva of the common Gnat floating in water, greatly magnified, aa, 

 the body and head of the larva ; 6, the respiratory apparatus, situated in 

 the tail ; c, the larva, not magnified. 







