NATURAL HISTORY. 513 



Order II. DIPTERA. (Gr. A/f, twice; Trrepov, a wing.) 

 Family, Culicidae. (Lat. Culex, a Gnat.) 

 CULEX. 



Family, CEstridse. (Gr. Olorpos, the Gad-fly.) 

 CESTRUS. 



Pipiens (Lat. humming), the Gnat. 



Bovis (Lat, of the Ox), the Gad-fly. 



The insects of this order possess but two wings, the place 

 of the others being supplied by two little organs something 

 like drum-sticks, called "balancers." Without these the in- 

 sect seems to be unable to direct its flight. 



All are familiar with the COMMON GNAT. This pretty tor- 

 mentor passes its larval existence in the water, in which state 

 thousands may be seen 'in any uncovered water-butt, wriggling 

 about with the most untiring energy, or reposing head down- 

 wards, only leaving the end of the tail at the surface. The 

 reason for this is very curious. This larva breathes through 

 its tail, and is moreover enabled by means of a fringe of hairs 

 to carry air down with it. 



It is a singular circumstance, that although the larva lives 

 in the water, yet were either the eggs or the perfect insect to 

 be submerged, they would be destroyed. The instinct of the 

 Gnat in order to fulfil all three conditions is very beautiful. 

 Whe.n the Gnat wishes to deposit its eggs, it rests on a leaf 

 or twig on the surface of the water ; it then takes each egg 

 separately, and fastens them side by side in such a manner 

 that they actually form a little boat, which will neither fill 



