136 BEITISH OAK GALLS. 



Average dimensions of a mature specimen. — Height, 



"5 mm. : diameter. 3 mm. 



May be sought dm-iug the moutlis of May to October. 



Growth is complete by the end of May. 



The typical condition of the gall is unilocular and unilarval. 

 Many galls, although externally in every way normal, and without 

 any trace of opening, are quite empty. 



The larva pupates in the gall. The imago emerges during 

 June. 



Alternate agamic generation : Neuroterus numismatis, 

 Oliver. 



Dr. Trail appears to have been the first in Britain 

 to find, and to record the occurrence, of this species. 

 On Jidy 5th, 1873, he "observed specimens on leaves 

 of the common oak at Banchory," where he had " seen 

 a few about a month before in their earlier stages, 

 without recognising them as galls." On the 27th of 

 the same month and year, Miss E. A. Ormerod, LL.D., 

 observed the gall on leaves of Q. peduncidata, " and 

 noted it as affectino- both sides of the leaf." 



During the earlier stages of growth the gall is 

 somewhat difficult to detect, but as development 

 (which is rapid) proceeds, both upper and under- 

 surfaces of the galled portion of the leaf project 

 convexedly, and from green, the colour soon passes to 

 grey or whitish. By then, a small papilla will have 

 manifested itself on the summit of the supra con- 

 vexity, and from it to the circumference, a number of 

 narrow ridges radiate. The radii are not always 

 continuous from the margin to the centre. Although 

 the opposite surface is typically less distinctly marked, 

 many specimens exhibit both papilla and radii with 

 equal clearness, while others are quite smooth. 



The larva occupies the whole of the cavity, there is 

 no inner gall. When mature the imago eats its way 

 out through either surface, and the gall will continue 

 to grow after the tenant has vacated it. An inquiline 

 (a Si/nergns), and a parasitic Torfjmua, are knoAvn to 

 inhabit the g-all. 



The periphery of the gall is circular, or oval, and, 



