152 BRITISH CICADJ3. 



ON THE STEEILIZATION OF TETTIGID^ BY 

 CEKTAIN INSECTS. 



On page 36 of this present volume, I have described 

 some of the parasitic insects whicli infest the Tettigidse; 

 and I have also alluded to some interesting notes, made 

 by M. Alfred Giard, which are recorded in the July part 

 of ' Les Comtes Eendus ' for 1889. The researches of 

 this observer may be regarded as a continuation of 

 those noted in the memoirs of Perris and of Dr. J. Mik 

 on the like subjects. 



In addition to the identification of certain parasitic 

 species of Hymenoptera and Diptera, and an account 

 of their several economies, our interest is excited by 

 the recent notice of the destruction that these insects 

 effect on the reproductive organs of their unfortunate 

 hosts. This action appears to result in the entire 

 sterility of the latter. 



M. Giard noted that the chestnut trees (marrouiers) 

 in the garden of the Luxembourg and in those of the 

 Bois de Meudon were attacked by thousands of small 

 flies, most of which were found dead, and attached by 

 their rostra to the under sides of the leaves. These 

 insects at first were referred by M. Giard to Tyjjhlocyha 

 rosce, Linn. ; but subsequently they were identified 

 with T. hippocastani and T. Douglasi of Edwards ; with 

 which species, externally, T. rosce may be easily 

 confounded. 



Most of these insects were deformed by an attach- 

 ment to their abdominal rmgs of a shining black 

 somewhat V-shaped sac, very similar to that I have 

 figured on Plate D of this monograph. M. Giard 

 regards these cyst-like bodies as true animal galls ; 

 and he defines "les galles" as local, but persistent, 



