100 BRITISH OAK GALLS. 



seen that the larval chamber of this species is very 

 much larger than that of A. raJicis. 



The galls of B. apfera may readily be obtained by 

 removing earth with a small trowel, or a piece of stick, 

 from the side of a l^ank on which an oak tree is grow- 

 ing. A position similar to that depicted on Plate 

 XXXIII, will yield an abnndance of specimens. They 

 are always covered with earth — sometimes sparingly — 

 and nsnally at a depth of abont three inches. 



In the year 1873 some of these galls were fonnd on 

 the roots of Deodars at Wimbledon, and were exhil^ited 

 at a meeting of the Royal Horticnltural Society by Dr. 

 Masters. It was considered to be the first instance in 

 which a Cynips had been known to attack any species 

 of Conifer. They have since been found on the roots 

 of Prnmis, Fagus sylvatica, and Vitis vimfera. 



The male imagines are always alate, the females are 

 mostly apterous ; occasionally there are rndimentary 

 wings. IJpon leaving the gall the female creeps up 

 the bole of the tree, along a limb, and after choosing a 

 terminal bud, bores a large numl)er of holes with her 

 ovipositor ; the ova being afterwards pushed down the 

 holes until they form a mass at the base of the bud. 

 The operation of oviposition is sometimes very pro- 

 tracted. Dr Adler observed that one female occupied 

 eighty-seven hours in depositing 582 ova in two buds 

 ('Alternating Generations,' p 72). 



The presence of so large a number of ova (about 290), 

 and a corresponding number of holes, in so small a 

 bud as that of the oak, must inevitably injure the 

 interior, and extensive destruction of the tissues of the 

 plant does actually take place ; so much so that occa- 

 sionally the whole bud axis is cut through, and no gall 

 formation takes place. When, however, gall formation 

 begins the apex of the real bud is severed from its 

 twig, and, remaining loosely attached to the swelling, 

 is lifted up and retained for some time. See Plate 

 LVII, div. A. 



The beautiful photo-micrographs on Plate XXXII, 



