SERPHOID AND CHALCIDOID PARASITES OF THE HESSIAN FLY 29 



grain products which were infested by various insects common to 

 such products, and it was originally believed probable that the Ditro- 

 pinotus had issued from some one of these stored-product insects. 

 Later acquisition of what appear to be typical specimens of flavicoxus 

 from the wheat jointworm, accompanied by equally typical speci- 

 mens of aureoviridis, and the presence of distinct intergrades, con- 

 vinced the writer that the two were the same species; and in view of 

 the fact that the species has never been definitely reared from any 

 stored-product insect, it is now deemed likely that the specimens upon 

 which the name flavicoxus was based actually issued from some host 

 other than the insects infesting stored products. It is probable that 

 the grain room in question contained straw or chaff which may have 

 harbored either jointworms or hessian flies which were the source of 

 the Ditropinotus. 



HOSTS AND LIFE HISTORY 



In their paper dealing with the life history of D. aureoviridis, 

 Phillips and Poos stated that this parasite had been reared from 

 field-collected HarmoMta tritici (Fitch), H. vaginicola (Doane), H. 

 grandis (Riley), H. atlantica Phillips and Emery, and H. secalis 

 Fitch, and that they had induced it to breed in the laboratory upon 

 H. elymicola Phillips and Emery. They also stated that it sometimes 

 played the role of a secondary parasite through Homoporus chalci- 

 diphagus Ashmead and Eurytoma spp. As already indicated, 

 Phillips (1927) also recorded Eurytoma pavva Phillips as a host 

 of this species, and Hill and Smith (1928) recorded it as attacking 

 Phytophaga destructor. Its preferred host is, without much doubt, 

 the wheat jointworm, as Phillips and Poos have stated. 



The species is a primary, solitary, external parasite upon the larva 

 of Harmolita within its cell and develops in the same manner within 

 the puparium of the hessian fly. According to Phillips and Poos, 

 there are two complete generations arid sometimes a partial third 

 generation per season upon the jointworm, in the latitude of Vir- 

 ginia, the first appearing early in June and the second early in July. 

 They state that normally no males occur in the first generation and 

 that females seem greatly to outnumber males in succeeding genera- 

 tions. Males are not rare, however, the National Museum collection 

 containing at least 18 males as compared with about 70 females. 



The egg is deposited in the cell of Harmolita or in the puparium 

 of the hessian fly external to the host larva. Five larval instars 

 were observed and described by Phillips and Poos. The winter is 

 passed as a full-grown larva. 



DISTRIBUTION 



This parasite probably occurs throughout most of the wheat-grow- 

 ing region of the United States. Specimens have been identified 

 from the following States: New York, Pennsylvania, Maryland, 

 District of Columbia, Virginia, North Carolina, Alabama, Tennessee, 

 Kentucky, Ohio, Indiana, Michigan, Illinois, Missouri, Kansas, and 

 Oregon. No specimens have been seen from Canada, but it is not 

 unlikely that the species occurs there, since it is common in the 

 Great Lakes region of the United States. It is apparently not 

 present in California. 



