62 THE POTATO CROP. 



tunately there are several natural enemies, which keep 

 the undue increase of the aphides in check. The common 

 ladybirds (Goccinella septem-punctata, G. dispar) are the 

 best known to us ; these not only devour them, but lay 

 their eggs on the same leaf, so that their little black larvae, 



1 and 2. Eggs of insect (natural size and magnified). 3 arid 4. Larvae. 5 and 6. Pupje. 

 7. Double-spotted Ladybird (C. bipunctata). 8. C. dispar. 9. Large Ladybird (C. septein- 

 pwnctata). 



as soon as they are hatched, may find a supply of food 

 at hand. Amongst other insects charged with injuring the 

 potato, we find the Thrips minutissima; though fre- 

 quently found on the stem, and known to support itself 

 by suction, its numbers are never sufficient to affect the 

 plant to any sensible degree. The " ground fleas/' Smyn~ 

 thurus solani, and an allied genus called Podura, however, 

 frequently injure the plant considerably by feeding on the 

 pulp of the leaves. These are remarkably minute insects, 

 not bigger than a small pin's head, and are nourished by 

 eating the fleshy part of the leaves, thus materially inter- 

 fering with their vital functions. In Nova Scotia these 

 insects attack the cruciferous plants, whole crops of which 

 have been swept away while in their seed-leaf by their 

 attacks. These insects never appear on damp ground; 

 a thin layer of sea- ware spread over the drills is sufficient 

 to preserve them from a visit, or if salt is strewed on the 

 surface it absorbs moisture, and thus keeps the soil damp 

 enough to be distasteful to them. Various species of the 



