IN^SKCTS INJURIOUS TO WHEAT. 93 



drove of pigs avouM doubtless answer the same inirpose, 

 which is that of destroying the larvae lying free upon the 

 surface or barely embedded among the roots of the grass/' 

 Several of our common birds feed upon the maggots 

 and flies as well as a number of ground-beetles. The 

 maggots are also sometimes attacked by a fungous disease 

 which in the damp soil in which they live would doubtless 

 grow and spread rapidly. Altogether these different 

 enemies keep them so well in check that they rarely 

 become of importance. 



Wheat Joint-worms {Isosoma spp.). 



Injury. — During midsummer, shortly before harvest, 

 many of the ripening ears of wheat are seen to topjjle over 

 and fall to the ground, owing to the breaking of the stalk, 

 which has been weakened at one of the joints. Upon 

 examination several small gall-like cavities will be found 

 fractured at the broken joint, and at other joints will be 

 found small round holes leading to some of these empty 

 cells. Xow and then one will be found occupied by a 

 small larva or pupa, the cause of all the mischief. Very 

 often this injury becomes quite serious, affecting the crop 

 much as does that of the Hessian Fly, though late in the 

 season, and is often mistaken for the Avork of that species. 

 The Joint -worms, however, are larv^ of small hymen- 

 opterous insects which were at first supposed to be parasitic 

 upon the Hessian Fly, as they belong to a family, the 

 Clialcididce, most of the members of which are parasites 

 of other insects. They differ from the flies in having 

 four wings instead of two, and in many other structural 

 points, as shown by the illustration, belonging to the same 

 order as the bees, ants, and wasps. 



