180 ORDER DIPTERA. 



imago State, la this way the increase of several species of destructive flies is kept in check, 

 anil their excessive multiplication prevented. No doubt, also, unfavorable seasons operate 

 as a still greater means for preserving a balance between excessive multiplication and 

 entire extirpation. 



Dr. Eights, of Albany, has furnished me with the following communication respecting 

 the platygaster, a minute ichneumon fly. His remarks, and the facts stated, illustrate in a 

 striking manner one of the most important features in the insect world, the checks which 

 an- interposed to the excessive multiplication of the injurious kinds. 



Platygaster tipul.e ( Kirby). Jl7ieat-i7ridge Parasite. 



This insect, though exceedingly small in size, has claims to our consideration, which 

 should justly entitle it to an exalted station in the rank of public benefactors ; lor it has 

 had assigned to it the peculiar and important duty of keeping in proper subjection that 

 unrivalled pest of our fields, the wheat midge (Cccidomyia tritici). 



The female fly of this parasite bears some considerable resemblance to the winged ant, 

 and may frequently be seen in our neighborhood during the months of July, August and' 

 September, in the greatest profusion, when our pernicious devastator is most numerous ; 

 flying about the grasses, or running over the grains of wheat in search of the midge larva, 

 for the purpose of depositing in each a single egg, and by this means preventing an im- 

 mense number of them from developing themselves into a perfect state ; although when 

 seen thus abundantly, they have often been unjustly accused of being themselves the 

 authors of the mischief? 



This insect expands to only one line and a half in breadth. The 

 female is of a shining pitch black color, with long, ten-jointed, 

 flail-shaped antennae or horns, slightly clubbed at the ends. The 

 head is round or globose, with the eyes conspicuously placed on 

 the sides. The trunk is oval, and bears a scutel terminated by a 

 strong rusty spine. The body or abdomen is obovate, small, and 

 narrowed at the base, with a long curved oviduct, concealed, when 

 unemployed, in the abdomen. It has four- transparent wings without nervures, the superior 

 pair very large ; and the legs are strong, and of a bright ochreous color, with the thighs 

 and shanks clubbed : the feet are long, slender, and five-jointed. 



We regret that some means have not yet been discovered to multiply this interesting 

 little insect, and thus effectually preserve our wheatfields from the fearful depredations 

 of the midge. James Eights. 



