I>SYCH.E. 



A NEW PARASITE OF THE HESSIAN FLY. 



BY STEPHEN ALFRED FORBES, CHAMPAIGN, ILL. 



Parasitism of the winter brood of the 

 Hessian fly has been but rarely and 

 doubtfully reported, and so far as I 

 know, has not hitherto been strictly 

 authenticated. An observation re- 

 corded by Prof. Herrick in 1841^, 

 probably referring to the parasite now 

 known as Platygaster herrickil., 

 Pack., implies an abundant develop- 

 ment of that species in the hibernating 

 generation of the "fly," but this obser- 

 vation was almost certainly incorrect 

 in some respects, — as has been shown 

 by Mr. Howard,'^ — and has not been 

 verified in this particidar. 



The breeding of unknown parasites 

 from infested wheat in spring was re- 

 ported by the writer in 1SS5 ;^ but the 

 breeding cage management in this case 

 was not such as to make it certain 

 that these were derived from the 

 Hessian fly. The following instance 

 is, consequentl)', probably the first to 

 estal:)lish clearly the occurrence of this 

 phenomenon. 



From a field of wheat sowed after 

 oats and corn in the autumn of 1S86, 

 living plants containing numerous pu- 

 paria of the Hessian fly were sent to 

 me Mar. 15, 18S7, by my correspond- 

 ent Samuel Bartley, Esq., of Edge- 

 wjod, in southern Illinois. A number 



' Herrick, C : E. A brief preliminary account of Ihe 

 hessian-fly and its parasites. (A mar. journ. sci. and 

 arts, 1S41, V. 41, p. 153-158), p. 157. 



^ i Inward, L. O. (3d rept. U. S. entom. conim., 1SS3, 

 p. 219, foot note.) 



^Forbes, S. A. (14th rept. State entom. 111., p. 46, 

 fnot-note.) 



of these puparia were enclosed in a dry 

 vial ; and from them seven imagos of 

 Cecidomyia destructor emerged previ- 

 ous to the 33d of April. This vial 

 was not again examined until Oct. i8, 

 when seven proctotrupid parasites were 

 found in it — all dead. These belonged 

 to the genus Platygaster^ as limited 

 byFoerster* and Thomson,® and to a 

 species apparently undescribed. 



Platygaster hieinalis^ n. s. 



General surfiice smooth, shining 

 black ; head opaque, very slightly 

 pubescent, not cuboid, wider than 

 thorax, nearly twice as wide as long. 

 Temples narrow, vertex not margined, 

 but minutely transversely rugulose. 

 Front also transversely corrugated above 

 the antennae, this corrugation merging 

 in a general irregular lineation of the 

 face. Upper half of front regularly 

 convex, lower with a slight vertical 

 carina commencing between the bases 

 of the antennae. Ocelli not elevated, 

 lateral ones equidistant from the eye 

 and the median ocellus. 



Thorax short, deep, very convex, not 

 compressed ; prothorax minutely trans- 

 versely lineate at the sides ; meso- 

 thorax shining, ovate, broadest just 

 before wings, dorsum bare in middle, 

 elsewhere with sparse gray hairs, sides 

 more hairy in front. Parapsidal 

 grooves scarcely visible. Scutellum 

 semi-circular, vaulted, nearly hemi- 

 spherical, without angle or process, 



< Foerster, A. Hymenopterologische studien, heft 

 2, 1S50, p. loS and 1 1 5. 



^Thomson, C. G. Sveriges proctotrupcr. (Ofvers. 

 af Kongl. vetensk.-akad. fdrhandl., 1859, v. 16, p. 69-S7) 

 p. 83. 



