134 BRITISH OAK GALLS. 



Spathegaster verrucosus, Sclileclitendal. 



SiMihegaster verrucosa, Scliltdl., Mayr, Fitcli ; Dryojjhanta verru- 

 cosa, Mayr ; D. divisa, Cameron ; Spathegaster verrucosus, Adler. 



English name of gall. — "The Red Wart Gall." 



Position of gall. — Ou the leaf, and in axillary and terminal 

 buds. 



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



Colours. — Greenish-yellow, pink, orange, red, reddish-brown. 



Average dimensions of a mature specimen. — Height, 

 4 mm. ; girth, 6 mm. 



May be sought during the months of April to June. 



Growth is complete by the end of May. 



The typical condition of the gall is vmilocular and unilarval. 



The larva pupates in the gall. The imago emerges during 

 May. 



Alternate agamic generation : Bryophanta divisa, Adler. 



On the surface of the gall, and generally near the 

 apex, is a very small raised disc, or mamelon. Some 

 galls have more than one. Under magnification it is 

 seen to be a circular, or oval, elevation about 1 mm. 

 in diameter, with a depressed centre through which 

 the imago eats its way out. This mamelon is some- 

 what variable in colour, but when the gall is mature it 

 assumes the reddish-brown hue of its surroundings. 



This gall develops upon three different situations. 

 On the leaf from the end of the mid-rib, or the margin 

 of the blade ; at the termination of a twig, and, the 

 axillary bud. This is explained by Adler as being due 

 to the fact that D. divisa usually lays her eggs " in 

 the rudimentary leaves." A slight deviation from the 

 normal situation of the egg " makes all the difference 

 as to the positions of the gall. If the egg lies on the 

 point of a leaf, the gall develops on that spot, and the 

 full grown leaf bears a gall on its point ; but if the 

 egg lies deeper in the base of the leaf, the whole leaf 

 surface is absorbed, and the gall rests directly on the 

 shortened petiole. . . . the gall is merely substi- 

 tuted for the leaf. When the egg is sunk still deeper 

 into the axis of the bud the whole bud is absorbed in 



