164 SAWFLIES, ICHNEUMON FLIES, WASPS, ETC. 



kind has caused it to be suggested that we should 

 rear them. This matter seems rather hard to manage ; 

 also we do not often benefit much by upsetting the 

 regular balance appointed ; but it is often in our 

 power to follow up a hint of this kind, by remembering. 



Fig. 128.— Parasite Flies of Wheat Midge maggot, nat. size and 

 magnitied. 



that when an out-of-the-way insect enemy has ap- 

 peared, we may very likely be able also to introduce 

 its regular check, and leave the results to follow in 

 due course. 



Sometimes also a new infestation may be traced 

 home to the country from which it came by means of 

 its accompanying Parasites. In the memorable ap- 

 pearance of the Hessian Fly in this country, we had 

 no clue to lead us to the knowledge of whether it had 

 come from America or from the Continent of Europe, 

 until examination of its parasites showed that, with 

 the exception of one kind common to both Continents, 

 the others were not American, but Piussian. 



The Parasite FHes of Wheat Midge (figured) show 

 the shape of two other kinds of these minute Flies. 

 The Macroqlcucs, of the family of the Chalcididce 

 (Fig. 128: i), is supposed, from its habits, to destroy 

 the Midge-grubs ; and the Phtij(iastcr, of the family 

 of the Proctotrvpidce (Fig. 128: 2), has been watched 

 in its operations of laying one egg in each Midge- 

 grub it attacks. 



