272 



We have been able to procure in abundance and study more com- 

 pletely than has heretofore been done the parasites (Dipterous and 

 Hymenopterous) of Typhlocyba, up to the present considered as very 

 rare and captured here and there accidentally. 



We have been drawn also to occupy ourselves with some very curi- 

 ous effects of parasitic castration produced by these parasites on their 

 hosts. 



Typhlocyba sp., with yellowish or whitish elytra, form a small group of 

 species living often side by side on the same trees and presenting among 

 themselves a mimicry so perfect that it is almost impossible to dis- 

 tinguish them even by a very careful examination of the external 

 characters. To James Edwards, of Norwich, Eng., belongs the credit 

 of having recently attracted the attention of entomologists to the very 

 marked distinctive characters which one can draw from the form of the 

 genital armature of the male to separate these diverse species. 



Aided by the work of that acute investigator we have discovered 

 that the Typhlocyba of the chestnut, described in our first note under 

 the name of T. rosce L,, belongs in reality to two distinct species, viz, 

 T. hippocastani J. Edw. and T. douglasi J. Edw., which are equally com- 

 mon on the trees of the Luxembourg. 



These two species may be parasitized by Aplielopus and hy Ateleneura. 

 But Aphelopus infests especially T. Mppocastmii and much less often T, 

 douglasi. Ateleneura is found, on the contrary, almost always in T. 

 douglasi and very rarely in T. hippocastani. 



The females of T. hippocastani and T. douglasi are very difficult to 

 distinguish. However, with T. douglasi^ the ovipositor is more robust 

 and presents only one curvature, while that of T. hippocastani is more 

 slender and is doubly curved in the form of a cimeter. With individ- 

 uals of both species parasitized by Aphelopus, the ovipositor is generally 

 considerably reduced and incapable of puncturing. Ateleneura seems to 

 have much less influence on the development of that organ. 



The genital armature of the male presents some very salientdistinctive 

 characters. With T. douglasi^ the penis is simple and the lateral pieces 

 have the form of legs. The parasitic castration, whether by Aphelopus 

 or by Ateleneura, induces but very slight modifications. 



With T. hippocastani, the lateral pieces are slender, simple arcs, but 

 the penis presents a very complex structure, being terminated by a 

 very curious eight-branched fork. 



With males parasitized by Ateleneura, and especially with those in- 

 fested by Aphelopus, the penis suffers considerable reduction, having 

 but six, four, or even but three branches. The specific characters are 

 thus profoundly changed, and certain of these modified forms would be 

 confounded on superficial examination with T. rosew L. or T. lethierryi 

 J. Edw. 



Modifications not less great are observed in some singular organs of 

 which the existence in the case of the males of Typhlocyba has not yet 



