266 INSECT "WATER TRESPASSERS. 



waggling movements, bending themselves almost 

 double, and then suddenly straightening the body. 



Although they live in the water, and find their 

 food there, they cannot breathe in it as can those 

 larvae which respire by means of gills, and are obliged 

 to have access to atmospheric air, just as are the 

 aquatic insects which have been described. This is 

 done after a curious manner. The breathing- tubes 

 with which the whole body is permeated open into 

 -two large tubes, which run along the sides. These 

 tubes pass into the tail, and the orifice is surrounded 

 with a star-like fringe of radiating hairs. When the 

 larva wishes to breathe, it ascends to the surface, and, 

 head downwards, just protrudes the tip of the tail 

 above the surface, where it is upheld by the hairy 

 fringe. 



The process of breathing may be easily examined 

 by taking a little glass tube, such as is used by homoeo- 

 pathic chemists, heating it in a spirit lamp or a gas 

 flame, and squeezing it until it is nearly flat. If, then, 

 it be nearly filled with water, and a Gnat larva placed 

 in it, the creature can be examined with a tolerably 

 high power of the magnifying glass. Unless the 

 tube be flattened, the lens cannot be brought near 

 enough to allow of a sufficiently high power to be 

 used. 



After a while, the larvse assume the pupal state. 

 There is not very much difference in their appearance 

 or their actions. Their shape remains much the same, 

 except that the part which comprises the head and 

 thorax of the future insect, is now very large, seeing 

 that it contains the loug legs and wings. It still 



