152 THE OAK GALLS AND GALL INSECTS 



becoming purple when older, due to a rind which covers the 



galls. This peels off later, leaving the gall beneath brown and 



striated. Shape : That part of the gall visible through the split 



bark is conical in shape. The larval chamber is in the lower, 



deeply imbedded part, which is dilated. 



Imago. 



Colour : reddish-brown. Antennae : dark brown, paler at the base. Thorax : 

 median segment and basal scutellar sutures dark. Abdomen : reddish brown, 3rd 

 segment finely punctured. Legs : reddish brown. 



(11.) Sexual Generation. Ia. Andricus testaceipes (Htg.) 



Inquiline. Synergus apicalis (Htg.) 



Gall. 



A thickening of the leaf stalk or vein of the leaf contains the 

 gall lying within in a hollow chamber. I have found two 

 specimens in the shoot, which I at first mistook for A . tvilineatiis 

 (Htg.) galls. Colour : Yellowish green. 



Imago. 



Colour: black. Antennae: Dark. Basal joints paler. Thorax: May be 

 slightly hairy at the base of mesonotum. Abdomen : orange, darker above. Legs : 

 Orange yellow, the base of hind coxae brownish. 



Account of Generation Cycle. 



If the galls of ^. sieholdii, when mature, are kept through the 

 winter, the insects emerge in April or May. The buds are pricked 

 by them near the base, as in ^. vadicis (Fab). The resulting gall in 

 some cases resembles A. trilineatus, but the eggs are deposited in the 

 rudimentary leaves, the gall appearing usually in the veins and 

 petiole of the leaf. The flies from this gall emerge in August. 

 Oviposition takes place through the bark of young stems near the 

 ground, the eggs being laid as a rule in a ring. The bark begins 

 to swell in the autumn, but ceases to do so during the winter. 

 During May in the following spring the red conical galls appear, 

 the reddish rind covering the galls breaks off, and they mature in 

 June, but the flies do not emerge till the following April or 

 May. 



OCCURRENCE IN EPPING FOREST. 



Andricus sieboldii. Uncommon. I only met with a few 

 specimens of this gall growing from the stems of some old 

 pollard oaks. The galls, which were situated near the bases of 

 the stems, were old and dried up. 



