I54 THE OAK GALLS AND GALL INSECTS 



bark of stems or trunk. I have found the insects during early- 

 spring in a mature condition in the galls. 



OCCURRENCE IN EPPING FOREST. 



Andricus covticis. Very common, especially in the callus 

 formed by the exposed cambium where the bark of old trees has 

 split down. On account of their brown covering, these galls are 

 easily passed over, but after the insects have emerged they 

 present a very typical appearance, having a punctured rim 

 showing where the vascular bundles have passed through to 

 nourish the upper part of the gall. 



I have taken mature flies from these galls in February. 



Andricus gemmatus. Common. First appearance noted, 

 June 20th. 



I have sometimes found these galls on the leaf petiole. 



(13.) Agamic Generation. III. Andricus radicis (Fab.) 



Inquiline, Synevgus incmssatns (Htg.) 



Gall. 



Appears on the root of the oak, sometimes on the trunk of 

 the tree partly above ground. Galls which appear on the roots 

 may also be often exposed. Colour : White and soft at first, 

 varying with increasing age from yellowish pink to bright red,, 

 becoming brown and woody later. 



Shape and size differ considerably ; four or five galls often ap- 

 pear in one mass, though each gall can easily be separated. In 

 some cases the galls greatly resemble potatoes, but usually they 

 present a cracked and wrinkled appearance. Larval cells 

 numerous. 

 Imago 



Colour : Reddish brown. Abdo?nejt : Red. Antennae : Colour varies. 

 Basal 4-5 joints brownish red ; apex darker. Thorax [and head : Pubescent. 

 Mesonotum with a large central and two lateral dark lines. A dark transverse 

 line in front of the scutellum. Metathorax dark. Abdofnen may have a dark 

 blotch on the first segment. Legs : Reddish, base of coxae black, tibiae and 

 claws infuscated. IVings Hyaline, a few hairs sometimes present. 



(13.) Sexual Generation. IIIa. Andricus trilineatus 

 (Htg.) 



Inquilines. Synergus apicalis, S. vulgaris (Htg.), Ceroptres arator 

 (Htg.) 



