364 [Mat 



The radial area of Diastrophus alone, among the first section, would 

 remind of that of the new species, if the latter was not closed. The 

 abdomen of both sexes does not show anything of the great preponde- 

 rance of the second abdominal segment, characterizing both sexes in 

 Synergus and Ceroptres and the female sex in Aulax. Thus, in more 

 than one respect, this species seems to hold an intermediate position 

 between the two sections of Cynipidse. 



We have had occasion to remark, more than once, how important a 

 character the sculpture of the thorax is among the Cynipidse. In 

 many cases this sculpture characterizes the genus. The sculpture of 

 the thorax of our new species is very peculiar ; the surface is semi- 

 opaque and has a silky (sericeous) gloss, due to a microscopic coriace- 

 ous sculpture on the mesonotum and to exceedingly delicate aciculate 

 striae on the pleurae. Judging from Mr. Foerster's description of Pha- 

 nacis centaurese, it seems that the sculpture of its thorax is somewhat 

 of the same nature, and a closer comparison of his generic definition 

 leads to the belief that both species must be closely allied. Only the 

 minute ridges on the "apex" of the metathorax, mentioned by Fcerster. 

 do not exist in my species. 



Among the species of European Atilax, communicated to me by Dr. 

 Keinhard. there is one, A. hieracii ( Bouche) Hartig. which differs very 

 considerably from the three other species sent by him, (A. brandtii 

 Hartig. germanus Grir., and potentillx Vill.) Whereas the three latter 

 come within my definition of the genus A ulax, the former shows the 

 most remarkable analogy to the new species in question, bred from 

 Sinapis. The structure of the abdomen, the sculpture of the thorax, 

 the neuration, etc.. are very nearly the same. Now. the so-called Aulax 

 hieracii is said not to be a guest gall-fly, but a psenidous gall-fly, living 

 on Hieracium. This would establish a new point of relationship be- 

 tween it and the new North American species, as well as with Pha- 

 nacis. 



It seems, therefore, that we have here a group of species living on 

 different herbaceous plants and intermediate between the gall-flies of 

 the oak, the rose and the bramble on one side and the guest gall-flies 

 on the other. There is no doubt, that in the course of time, many 

 other species will be added to this group ; it may also happen, that 

 most of these species will have to be united in a single genus, or that 

 the definition of P'lanacis, somewhat modified, will apply to a number 

 or to all of them. Our data are too scanty to warrant, as yet, any con- 

 clusion, but we recommend the subject to the attention of observers 



