INSECTS, MITES, ETC. 



223 



gardens aud crops, it really does an immense amount of 

 good. Its good qualities consist, first of all, in draining 

 the soil, and, secondly, in helping to materially increase 

 its fertility. Thus, in the first case, its indefatigable 

 method of tunnelling the soil provides channels through 

 which the air and moisture can pass downwards from the 

 surface. The air which passes downwards acts beneficially 

 upon the stored-up elements in the soil, oxidising and 

 liberating substances for the sustenance of plant growth, 

 which would otherwise be unavailable. The rains, more- 

 over, which are enabled to pass through the tunnels are 

 charged with nitric acid, which, on coming in contact with 



[From Curtis' ' Farm Insects."] 

 DEW OR EARTH WORM. 

 1, Earthworm (Lumbriciis terrestrio) ; 2, Rings; 3, Head of the worm; 4 

 and 5, Eiggs of the worm. 



the soil, becomes converted into nitrogen, another valuable 

 plant food. Furthermore, the air and moisture help to 

 provide congenial conditions for the development and acti- 

 vity of those wonderful and minute organisms, the nitri- 

 fying bacteria. Without air the latter could not exist, and 

 without their presence in the soil plants could not thrive. 

 Nor is this all. By tunnelling and draining the surface, 

 water which would otherwise remain stagnant, seal up 

 the capillary tubes, and keep the temperature low, is 

 allowed to pass into the subsoil, leaving the surface drier 

 and warmer. Then, worms enrich the soil by ejecting 



