158 THE OAK GALLS AND GALL INSECTS 



Inquilines. Synevgns alhipes, S. facialis (Htg.), and S. radiatus 

 (Mayr.) 



Gall. 



Appears on the leaves, causing irregular thickening. An 

 inner oval yellowish gall contains the larva. These galls twist 

 and distort the leaves, which in some cases do not mature at all. 

 They are often numerous, causing continuous swellings. They 

 often appear on young twigs, twisting them and causing them 

 to grow in a permanently bent condition. 



Imago. 



Colour: Black. Antennae: Dark, pale at base; Apex gradually thickened. 

 Ihorax : Without sculpture, smooth. Abdomen : Black and shining. Legs : 

 Testaceous ; coxae always, and femora sometimes, dark. Wings : Hyaline. 



Account of Generation Cycle. 



When the A . collaris galls mature, a year and a half elapses 

 before the insects emerge. This takes place at the end of 

 March or the beginning of April. 



The eggs are laid in the rudimentary leaves at the centre of 

 the bud. These leaves are distorted and thickened by the 

 resulting A. cnvvator galls, which appear in May, the flies 

 emerging from them in June. These, after copulation, lay one 

 egg in each bud, the A. collaris galls appearing in September, 

 and sometimes in August. In October the gall falls to the 

 ground, but the flies do not emerge until March or April of the 

 second year. 



OCCURRENCE IN EPPING FOREST. 



Andricus collaris. Abundant. Tiiese galls do not always fall 

 to the ground when mature, but those that do not I have usually 

 found to be parasitised. First appearance noted, August 22nd. 



Andricus curvator. Very plentiful. I have occasionally met 

 with this gall on the fruit stalk at the time when the acorn has 

 just begun to form. The stalk is then bent nearly double, and 

 much thickened. This gall, however, is usually found on the 

 leaf. First appearance noted, May 14th. 



(16). Agamic Generation. VI. Andricus callidoma 

 (Thorns). 



Inquilines. Synergus nervosus (Htg.) and S. vulgaris (Htg.) 



