38 MISC. PUBLICATION 17 4, U.S. DEPT. OF AGRICULTURE 



that their development differs from that normal for parva. In the 

 fly puparium they could have no opportunity to feed on plant sap 

 and hence must develop entirely as animal feeders. Experiments 

 by Phillips, however, indicated that parva might be able under some 

 circumstances to develop entirely as a plant feeder, while in another 

 experiment a second-instar larva of E. parva which had already con- 

 sumed a young larva of Harmolita and had begun to feed on plant 

 sap is said to have been transferred to a full-grown larva of H. 

 tritici, on which it was reared to maturity. If it is true that the 

 larva of E. parva is capable of adapting itself to a wholly phyto- 

 phagous, wholly entomophagous, or a partly phytophagous and 

 partly entomophagous development, then it is possible that the para- 

 sites of the fly here described as atripes are merely individuals of 

 parva which have been somewhat reduced in size and otherwise 

 slightly modified by the circumstance of their development on the 

 limited amount of food represented by a single fly larva. In the 

 absence of complete proof that E. parva is capable of such wide 

 adaptability in its mode of development, and in view of the apparent 

 though slight differences which do exist, it is deemed better for the 

 present to treat this parasite of the hessian fly as different from 

 parva. 



HOSTS AXD LIFE HISTORY 



As already indicated. 22 specimens of E. atripes have been reared 

 from Phytopkaga destructor and 1 from Cephu-s cinctus. It is 

 doubtful, however, if either of these insects is the normal host, and it 

 is believed likely that future studies will reveal it to attack some 

 other grass-infesting species. 



Little can be said of its life history other than that it emerges 

 from the fly puparium as an adult. Manuscript notes by Myers show 

 that the examinations made by him of puparia from which this 

 Eurytoma emerged indicated that the parasite in every instance had 

 developed as a primary, solitary parasite feeding externally upon the 

 fly larva within its puparium. 



DISTRIBUTION 



As will be seen by reference to the type material, this species has 

 been taken in the Pacific Coast States of Washington and Oregon, in 

 the northern Central State of Xorth Dakota, and in the Eastern 

 States of New York, Pennsylvania, Maryland, Tennessee, and Ohio. 

 These records indicate a probable distribution over most of the 

 wheat-growing region of Xorth America. 



IMPORTANCE 



The fact that so few specimens of this species have been obtained 

 during the many years that the fly has been studied demonstrates that 

 it is of little importance as a parasite of the hessian fly. 



DECATOMA AMSTERDAMENSIS Girault 



(Fig. 9) 



Decatoma amsterdamensis Girault. Descriptiones stellarum novaruin, p. 10, 

 1917; Leonard. N.Y. (Cornell) Agr. Expt. Sta. Mem. 101: 976, 192S ; 

 Balduf. U.S. Natl. Mus. Proc. 79 (art. 28) : 20, pi. 1, fig. 4, 1932. 



