128 BRITISH OAK GALLS, 



Position of gall.— Mostly iu termiual, but also iu axillarv 

 biids. 



Manner of growth. — Single, solitary, glabrous, vesiculate, 

 ovoiil. 



Colours. — Pale greeu, greenish-yellow, j)ale pink, light brown. 



Average dimensions of a mature specimen. — Height, 

 8 mm.; girth. 15 mm. 



May be sought during the months of April and MaA'. 



Growth is complete liy the end of May. 



The typical condition of the gall is unilocular and unilarval. 



The larva pupates in the gall. The imago emerges during 

 May. 



Inquilines, Nos. 17, 72. 



Alternate agamic generation : r Neuroterus ostreus, Hartig. 



The dimensions of the hirgest gall of this species, of 

 which I have a record, is — heig^ht 15 mm., orirtli 

 21 mm. 



The proportion of axillary Ijuds containing galls, 

 as compared with terminal bnds, is one in fonr. 



" There seems to be some doubt as to the agamic 

 form of this species." Beyerinck bred Xcuroteruii 

 Aprilinns from galls of Andricus solitarius. Von 

 Schlechtendal and F. Loew consider N. SehlechtendaJi 

 the agamic form. Mayr considers, " that ostreus, 

 being an Andricus, can hardly l)e the agamic of a 

 Neuroterus'' ('Brit. Phyto. Hymen.,' vol. "iv, p. 140). 

 Adler is strongly of opinion that it is N. ostreus, and 

 his experience and experiments entitle him to be 

 regarded as correct. 



Probably no other British oak gall equals this 

 species in the rapidity with which it develops, and 

 reaches maturity. It is also one of the most obscure 

 as reofards its situation. The enfoldino- leaf-bud 

 scales, and the very few days required for it to become 

 mature and shrivel, coml)ine to render its discovery a 

 difficult matter, overcome mainly by experience. 

 Four or five days only, are necessary, from the time 

 the gall expands sufficiently to increase the size of the 

 bud, until growth ceases, and the imago escapes. 



