82 liRITlsH OAK GALLS. 



about 8 mm. alcove its surroundings, by wliicli time it 

 will have altered to a l)rownish colour, and the texture 

 hard and woody. 



The cap is concave within, and soon after the gall 

 reaches maturity it falls off, leaving the larval chamber 

 with a A^ery thin Ijut hard convex septum upon it, and 

 the upper margin of the thick cell walls exposed. The 

 imago ultimately eats its way thi-ough the septum. 



The exposed margin is l^ordered l)y a thin rugged 

 rim, within which is enclosed a circle of about twenty 

 small punctures, with the hole of emergence in the 

 centre. These little punctures " belong to an earlier 

 period of growth ; and through them passed the 

 vascular bundles that nourished the upper sappy half 

 of the gall" ('Alternating Generations,' p. 38). 



Miss E. A. Ormerod appears to have been the first 

 to discover and record this gall in Britain, and also to 

 figure a type specimen in two conditions of growth 

 from a cluster found in 1877, in the neighbourhood of 

 Isleworth. 



An oak stump in a coppice or a wood is one of the 

 surest situations in which to find these galls, more 

 especially if there be a number of small boughs 

 growing from the stump. A careful scrutiny should 

 also be made of trunks of old trees. AVhen in clusters 

 and exposed, as shown in the centre of Plate XIX, 

 they are not difficult to find, but if a gall is solitary, 

 and in the folds of a callus, as seen near the top of the 

 same illustration, detection is less easy. After they 

 have turned brown, or if surrounded by moss, they 

 may very easily be overlooked, and on that account 

 their distril3ution may be much wider than is generally 

 known. 



Aphilothrix fecundatrix, Hartig. 

 (Plates XX, XXI, XXII, div. B.) 



Cynips gemmie, Linn., Sclmck. ; C./ec?<w(ZairLT, Hartig, Marshall, 

 Miiller ; Aphilothrix gemniie, Mayr, Fitch; Aph. fecundatrix, Kdler, 

 Licht. ; Andricvs fecnndatrix, Mayr, Cameron; A. gemmce, Mosley. 



