Miscellaneous. 479 



with his researches the Ti/phloci/bce of the horse-chestnut indicated 

 in the former note as T. rosce, Liuu., really belong to two distinct 

 species, viz., T. hippocastani, J. Edw., and T. Douglasi, J. Edw., 

 which are equally common on the trees of the Luxembourg. These 

 two species may be attacked by the two parasites here mentioned ; 

 but the Aphelopus especially infests T. hippocastani, while the 

 Atelenevra almost always occurs in T. Douglasi. 



The females of T. liippocastani and T. Douglasi are very difficult to 

 distinguish ; nevertheless in the latter the ovipositor is more robust 

 and presents only a single curvature, while in T. hippocastani it is 

 thinner and doubly curved in the form of a scimitar. In individuals 

 of both species parasitized by Aphelopus the ovipositor is generally 

 much reduced and incapable of penetration, but Atelenevra seems to 

 have much less influence on the development of this organ. 



As regards the male genital armature, in T. Douglasi the penis is 

 simple and the lateral pieces have the form of legs ; parasitic castra- 

 tion, whether by Aphelopus or Atelenevra, causes very slight modifica- 

 tions in it. In T. hippocastani the lateral pieces are simple and 

 slender arcs, but the penis presents a very complex structure and 

 terminates in a fork with eight branches of very elegant form. In 

 the males parasitized by Atelenevra, and especially in those infested 

 by Aphelopus, the penis undergoes considerable reductions ; it has 

 sometimes six, sometimes four, and sometimes only three branches. 

 The specific character is thus greatly modified, and some of the forms 

 might easily be confounded with T. rosce, Linn., or T. Lethierriji, 

 J. Edw. 



Modifications of equal extent occur in certain singular organs, the 

 existence of which in the males of Tgphlocgha does not appear to 

 have been noticed, and of which the function is quite unknown. 

 These are two invaginations of the ectoderm which start from the 

 ventral surface of the first abdominal segment and extend like the 

 fingers of a glove to the extremity of the foui-th segment or a little 

 further. The author regards them as homologous with the stridu- 

 lant organs of the male Cicadas, In the males of T. Douglasi and T. 

 hippocastani infested by Aphelopus or Atelenevra the ventral invagi- 

 nations are much reduced, reaching only, in general, to the second 

 abdominal segment, and often forming only two little pockets on the 

 first segment. 



Aphelopus melaleucus appears to be pretty common ; it has been 

 met with at Wimereux and in the wood at Meudon upon T. hippo- 

 castani and T. ulmi, which often live together upon the elm, with 

 T. opaca, J. Edw. In these localities the sac which contains the 

 larva instead of being yellow as in the Luxembourg garden, is usually 

 of a blackish colour. This colour is evidently protective of the more 

 numerous individuals living upon T. ulmi, the abdomen of which is 

 black, and is jDrobably due to heredity in the others. Perhaps, 

 moreover, Aphelopus presents varieties in the different species of 

 Typhlocgba which it infests : Walker has described fifteen forms of 

 this Hymenopteron, and the individual figured by him differs in 

 certain characters from those examined by the author, who says 

 that he has been unable to find the least trace of the cells of the 

 fore wings, and that the palpus possesses only five joints instead of 

 six. — Comptes Rendus, Nov. 4, 1889, p. 708, 



