370 Journal of Agricultural Research voi. vi, no. io 



EUPELMUS ALLYNII 

 THE EGG 



The egg of E. allynii French (PI. LI, fig. i) is elliptical in shape, with a 

 thin stalk of varying length on one or both ends. In some cases the stalk 

 seems to be entirely absent from one end. The egg is grayish white in 

 color. The long axis of the body of the egg averages 0.35 mm., the short 

 axis o. 1 4 mm. in length. As a parasite of the Hessian fly, the observations 

 at Wellington, Kans., indicate that the egg is normally deposited in the 

 puparium of the host. Females were repeatedly observed by Mr. E. O. G. 

 Kelly and the author to be ver}^ numerous in fields, ovipositing in Hessian- 

 fly flaxseeds where these constituted the only stage of the fly to be found. 

 In one instance, however, a wheat stem containing nearly grown Hessian- 

 fly larvae, but no flaxseeds, was placed in a vial cage containing females 

 of E. allynii. Upon dissecting this stem two eggs of this parasite were 

 found inside the leaf sheath close beside the Hessian-fly larvae. Whether 

 or not the parasite is able to complete its development on Hessian-fly 

 larvae before they have formed puparia is still unsettled. 



Hundreds of flaxseeds in which E. allynii had oviposited have been 

 dissected and the eggs of the parasite have always been found inside the 

 puparium but external to the inclosed Hessian-fly larv^a or pupa. Some- 

 times they were unattached, but more often the egg was fastened to the 

 inner surface of the puparium by a little netlike structure made apparently 

 of fine, white threads tangled together (PI. LI, fig. 2). The threads form- 

 ing the net appeared to be identical in diameter, color, and material with 

 the egg stalks. The edges of this little net or mat were fastened down all 

 around the egg, holding it securely in place. Sometimes the net was 

 partly fastened to the host larva in addition to the puparium. In all 

 experiments E. allynii oviposited seemingly indiscriminately in flaxseeds 

 already containing parasite larvae as v^-ell as in those containing Hessian- 

 fly larvae. The incubation periods of 109 eggs varied from 1% days to 5 

 days. The egg stage was shorter in summer temperatures, observations 

 being made during a period from July to November. 



THE LARVA 



Upon becoming fully formed inside the egg the larva (PI. LH, fig. 2) 

 breaks through one end of the chorion and after crawling around a little 

 attaches itself to the external surface of the host larva. The parasite 

 lai'va bears strong mandibles and feeds externally on the Hessian fly by 

 puncturing the epidermis of the host and sucking out the body liquids. 

 Larvae reared in glass cells became full grown in from 7 to 10 days. 

 After becoming full grown many of the lar\'a£ were inactive for months; 

 others pupated at once. In the warm summer temperatures most of the 

 larvae reared pupated at once upon completing their growth, while larvae 

 reared in the fall pupated only in occasional instances. 



