ENEMIES OF THE HESSIAN FLY. 587 



egg is hatched a little maggot, which devours the pupa of 

 the Hessian fly, and then changes to a chrysalis -within the 

 shell of the latter, through which it finally eats its way, 

 after being transformed to a fly. This last change takes 

 place both in the autumn and in the following spring. Some 

 of the females of this or of a closely allied .species come 

 forth from the shells of the Hessian fly, without wings, or 

 with only very short and imperfect wings, in which form 

 they somewhat resemble minute ants. 



Two more parasites, which Mr. Herrick has not yet 

 described, also destroy the Hessian fly, while the latter is 

 in the flax-seed or pupa state. Mr. Herrick says, that the 

 egg-parasite of the Hessian fly is a species of Platygaster, 

 that it is very abundant in the autumn, when it lays its 

 own eggs, four or five together, in a single egg of the Hes- 

 sian fly. This, it appears, does not prevent the latter from 

 hatching, but the maggot of the Hessian fly is unable to 

 go through its transformations, and dies after taking the 

 flax-seed form. Meanwhile its intestine foes are hatched, 

 come to their growth, spin themselves little brownish co- 

 coons within the skin of their victim, and, in due time, are 

 changed to winged insects, and eat their way out. Such 

 are some of the natural means, provided by a benevolent 

 Providence, to check the ravages of the destructive Hessian 

 fly. If we are humiliated by the reflection, that the Author 

 of the universe should have made even small and feeble 

 insects the instruments of His power, and that He should 

 occasionally permit them to become the scourges of our race, 

 ought we not to admire His wisdom in the formation of 



O 



the still more humble agents that are appointed to arrest 

 the work of destruction ? 



The wheat crops in England and Scotland often suffer 

 severely from the depredations of the maggots of a very 

 small gnat, called the wheat-fly, or the Cecidomyia Tritici 

 of Mr. Kirby. This insect seems to have been long known 

 in England, as appears from the following extract from a 



