88 



COEN AND GRASS. 



attack, whilst one a fielJ or two off, iu a more suitable 

 position, is as well as could be wished. 



Parasites. — It is not necessary here to enter in detail on 

 the subject of parasites infesting the Hessian Fly, as it is im- 

 possible for any one without good knowledge of the subject 

 aided by type specimens, descriptions, and fairly good (or 

 rather powerful) magnifiers to identify them trustworthily. 

 Those who wish to study them wall find descriptions in 'Die 

 Pteromalinen der Hessenfliege von Prof. K. Lindeman,' Moscow, 

 1887, and in the publications of Prof. C. V. Riley (Entomolo- 

 gist of U.S.A. Department of Agriculture) "On the Parasites 

 of the Hessian Fly." 



Our own parasites of this Cccidomyia destructor were deter- 

 mined first by means of specimens bred in this country, 

 which I forwarded to Dr. Lindeman (above mentioned), who 

 identified them, and who was good enough to send a set of 

 specimens of Piussian parasites to Prof. Piiley and one to myself. 



The subject was gone into with the most extreme care by 

 Prof. Piiley, during his stay in England in 1887 ; and I have 

 in my possession the long detailed communication he was 

 good enough to give me, containing his most valuable obser- 

 vations as to identity, synonyms, slight or important varia- 

 tions in our British parasites considered with reference to 

 published descriptions, to wdiich he appended the remark : — 

 " Thus every one of Lindeman's forms have been reared in 

 England. I should not have been able to speak so positively 

 without his types, wdiich he has been kind enough to send 

 me," . . .— (C. V. E.) 



In the pamphlet by Dr. Lindeman, ' On the Pteromali of 

 the Hessian Fly ' (pp. 14 and 15), above alluded to, he gives 

 the following observation as the result of his examinations : — 

 " That the larva; of the Cecidomyia destructor in North America 

 and in Eussia are certainly infested by Pteromali of the same 

 genus, but do not produce any identical species, as is shown 

 by the following comparative lists : — 



Larv/E are infested in N. America 



BY 



1. Merisus destructor, S. 



2. i)/. snhajytenis, Eil. 



3. I'etrasticlius pwductus, Kil. 



4. Ev2)el»iuti alli/nii, Fr. 



5. riatygastcy Iwrrickii, Pask. 



Larvae are infested in Russia 



BY 



1. Merisus intermedius, Lindmn. 



2. Tetrasticlms rilciji, Lindmn. 

 B. luqu'lmus liarscliil, Lindmn. 



4. Flatijgaster viinutus, Lindmn. 



5. Semiotellus nigripeit, Lindmn. 



6. Euryscajnis saltatus, Lindmn. 



7. Flatijgaster ? sp." 



Dr. Lindeman's list of the Eussian parasites is that of 

 which I have the advantage of possessing Prof. Eiley's 

 commentary. 



