186 BRITISH OAK GALLS. 
. Average dimensions of a mature specimen. — Height, 
‘5mm.; diameter, 3mm. 
May be sought during the months 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: Newroterus nuwmismatis, 
Oliver. ; 
Dr. Trail appears to have been the first in Britain 
to find, and to record the occurrence, of this species. 
On July 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. pedunculata, “ and 
noted it as affecting both sides of the leat.” 
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 Synergus), and a parasitic. Torymus, are known to 
inhabit the gall. 
The periphery of the gall is circular, or oval, and, 
