REPORT OP THE STATE ENTOMOLOGIST 1901 



721 



cular hole in the side has produced a parasite and not a fly. 

 Sometimes fully nine tenths of the Hessian flies are destroyed 

 by parasites and occasion- 

 ally entomologists have ex- 

 perienced difficulty in breed- 

 ing any adult flies from 

 infested wheat stems be- 

 cause the parasites were so 

 numerous. 



The above notes give some 

 idea of the importance of 



these little Creatures. One Fig. 2 Merisus destructor (after Riley) 



of the most efficient of these parasites is known as M e r is u s 

 destructor Say, a minute four winged fly which is repre- 

 sented in the accompanying illustration. It occurs not only 



Fig. 3 Boeotomus subap- 

 terus (after Riley) 



Fig. 4 Platy gas ter herrlckii Pack, (after Riley) 



throughout the American territory affected by the Hessian fly 

 but it is known in England and Europe. 



Another parasite which ranks next in economic importance to 

 the preceding is known as Boeotomus subapterus. It 

 is frequently wingless as seen in fig. 3. The proportion of 

 winged to wingless individuals is said to vary at different sea- 

 sons of the year. In Missouri this species has been bred from 

 infested wheat stalks more commonly than the preceding. 



Platygaster herrickii Pack., represented in the 

 accompanying figure, is another common parasite of this grain 

 pest. 



