THE ENTOMOLOGIST. 



51 



a yellowish colour ; in the space between them and the 

 margin is a circle of scabrous points. In the interior is a 

 large larva-cell, and a hole in the convex septum shows 

 where the imago has escaped. — G. L. Mayr. 



Aphilothrix Corticis is accompauied in the gall by Synergus 

 incrassalus, which has already beeu mentioned as a tenant in 

 the gall of Aphilothrix Radicis, and is one of the winter 

 species, Dr. Mayr having divided the Synergi into winter 

 flies and summer flies according to the time of their appear- 

 ance. The following note refers to the likeness of oak-galls 

 to organs of the oak. The differences of the parts of an 

 organism, such as the oak, and the means which successively 

 occasion these differences, are of much interest, as the result 

 of one agent, — the circulation in the living form. But the 

 differences between the kinds of oak-galls are more remark- 

 able : they are also the products of the circulation of the oak, 

 and therefore it would seem to be likely that they must 

 resemble the native products of that circulation ; and such in 

 some kinds is the case. But two kinds of galls, quite different 

 in structure, may be found in close contiguity, or almost 

 connected, on the oak ; and it remains to be ascertained 

 whether this difference is caused by the puncture, by the egg, 

 by the grub, or by the joint influence of these three. — Francis 

 Walker. 



ApJtilothrix JRhizomatis. — This occurs 

 partly under ground and partly on those 

 shoots which are but slightly raised above 

 the ground : a roughness or uuevenness in 

 the bark is observable, and a crack or 

 furrow appears, in which the galls are 

 seated in sparse clusters : the visible por- 

 tion of each gall is conical or hemispherical, 

 or sometimes nearly oval, and of un ochreous 

 colour ; at the base of the cone are striaj or 

 furrows, similar to those on the species next 

 to be described, but these vanish towards 

 the summit, where no trace of such stria) 

 is perceptible ; the summit itself is rounded, 

 and is pierced in the centre by the imago 

 in making its escape. Each gall contains 

 one large larva-cell, the exposed portion of 

 which is from two to three millemetres in ^^ ehizomatis. 



Fipr. 4. 



