54 BRITISH OAK GALLS. 



Colours. — Pale green, dark green, l)r<:)-wn. 



Average dimensions of a mature specimen. — Height, 

 2 mm. ; length, 1 mm. ; girth, 3 mm. 



May be sought during the months of April (late), May, and 

 June. 



Growth is complete l\v the end of May. 



The typical condition of the gall is unilocular and unilai-val. 



The larva pupates in the gall. The imago emerges during 

 June. 



Alternate agamous generation : Aphihthrix calUdoma, 

 Hartig. 



This gall does not appear to be very widely 

 distributed tliroughoiit Britain, or it may be, that by 

 reason of the inconspicuous habitat, as well as its 

 small size, it has been overlooked, or confused wi^h 

 that of A. ramuli. 



The imagines of callidoma apparently prefer to 

 oviposit in catkin buds situated high up in the 

 tree, where, without the aid of a pruner, they are 

 unattainable. I have only once found them within ten 

 feet of the ground. Upon the same tree, with field- 

 o-lasses, numerous others could be seen twentv and 

 thirty feet higher up. 



" The gall is placed on the stalk of the male catkin ; 

 at its base two shallow impressions may be recognised 

 Avhich are derived from the sutures of the anthers 

 from which the gall sprang. The galls are often 

 placed so closely together that they appear to form 

 one woolly mass '•' (' Alternating Generations,' p. 54). 



The affected catkins are co]isiderably shortened and 

 seldom project beyond the bud, while others growing 

 from the same stem attain normal dimensions. 



The shape of the larval chamber is oval ; the 

 diameter of its long axis is about 2 mm. It is rounded 

 at the base and apex ; from the former spring a few 

 lono- white hairs which are three or four times longer 

 than the gall. The gall grows quickl}^, reaches 

 maturity in about twenty days, and then falls to the 

 o-round. 



It may be distinguished from A. rariivli because it 



