THE WHEAT CROP. 75 



well as birds devour enormous quantities of them, and a 

 small ichneumon fly (Proctotrupis viator) eagerly searches 

 after them in every chink of the surface soil. 



Numerous remedies have been suggested to counteract 

 the damage they inflict on our crops. 1 Deep cultivation 

 brings them up to the surface in winter, and gives both 

 the birds and the weather more chance to destroy them. 

 Rolling the crops attacked with a ribbed or grooved roller 

 obstructs their ready passage through the soil, and forces 

 them up to the surface, where they are more exposed, and 

 where they may frequently be handpicked, especially if 

 slices of potatoes or turnips be placed on the ground. In 

 the transactions of the Entomological Society, details are 

 given where no less than 12,000 were thus picked off a 

 single acre. Topdressings of various kinds have also been 

 recommended, though their action does not appear very 

 clear. There are some forty species of elaters, whose 

 larvae (wire worms) are known to be injurious to our 

 crops. 



Among the insects infesting our wheat fields, the 

 ''wheat midge" (Cecidomya Tritici) is the best known. 

 Those persons who pay attention to what is going on in 

 the fields, must often have seen, in the evenings of early 

 summer, myriads of minute, gnat-like flies swarming over 

 the wheat crops, which they select as the most suitable 

 spots for depositing their eggs. These are deposited in 

 the culms while the wheat is in flower, and when they 

 are hatched, the little lemon- coloured larvae abstract the 

 juices, and cause the grain to shrivel. Nothing is more 

 common, if you examine an ear of! wheat, than to find one, 

 two, or more of the grains defective, or entirely destroyed 

 by the attacks of the larvae of this insect. When full- 

 grown, they either enter the earth to become pupce, or 



1 Curtis estimates the quantity of wheat seed destroyed by this insect alone 

 at C0,000 bushels. 



