50 THE OAK GALLS AND GALL INSECTS 



Account of Generation Cycle. 



The perfect insects emerge from the Dryophanta divisa galls^ 

 and at once proceed to prick the buds. This happens in 

 October, near the end of the montli, and at the beginning of 

 Novem.ber. In the following May the galls of Dryophanta 

 verrucosus appear. They may develop on the leaf or from the 

 bud direct. From these galls the perfect insects of the sexual 

 generation emerge at the end of May, and lay their eggs in the 

 tenderest leaves, Dryophanta divisa galls appearing at the end of 

 July. 



OCCURRENCE IN EPPING FOREST. 



Dryophanta divisa. Not plentiful, though I found them in 

 some cases in numbers on the leaf. First appearance noted, 

 July 19th. 



1 was unable to obtain any specimens of Dryophanta 

 verrucosus. 



(10.) Agamic Generation. IV. Dryophanta agama (Htg.) 

 Inquilines. Svnergus pallicornis and S. alhipes (Htg.) 

 Gall. 

 Shape : Circular. Found on the under-surface of the leaves 

 emanating from the leaf veins. Central hollow large ; walls thin. 

 Colour : Pale yellow, but many have a pale pink or reddish tint, 

 becoming browner with age. 



Imago. 



Coloi4r: black. Antennae'. I2th antennal joint longer than broad ; a 

 variable number of basal joints may be reddish. Thorax : More glabrous than 

 in preceding species. Abd()?nen : Black. Tegs : Yellowish red, base of coxae 

 usually darker in colour. 



There is no known sexual form, though it is probable that 

 another generation exists. 



The galls are found towards the end of July and in August 

 on the veins at the back of the oak leaves. They can be easily 

 distinguished from D. divisa by their smaller size, rounder shape, 

 and larger larval cavity. The flies emerge in November. 



OCCURRENCE IN EPPING FOREST. 



This gall was not abundant but more frequently met with 

 than Dryophanta divisa. First appearance noted, August loth. 



