OF EPPING FOREST. . I55 



Gall. 



Found in shoots of one year's growth, giving in some cases an 

 uneven appearance ; in others their presence is only noticeable 

 after the insects have emerged by the small round holes in the 

 shoots. 



Imago. 



Very variable. Colour : Brownish-reel. Antennae : Dark. Legs : Testaceous, 

 hind coxae dark. TVings : Hyaline. Thorax and Head marked with, or almost 

 entirely, black. Abdomen : Dark. The male dififers from above in being more 

 shining and having the legs of a dusky orange colour, the coxae, hind tibise and 

 femora darker. Head, thorax, and abdomen usually quite black. 



Account of Generation Cycle. 



The asexual flies emerge from the A. mdicis galls usually in 

 April or May ; and after resting, deposit their eggs in the base of 

 the buds, the resulting galls appearing in the twig. Sometimes 

 I have found the flies ovipositing as late as the middle of June, 

 when the bud has partially developed. In either case the galls 

 formed are A. tvilineatus. When oviposition takes place as late as- 

 June, the galls are easily recognisable, as the eggs are crowded 

 into one shoot, causing it to swell considerably. The sexual 

 flies emerge from these galls, and oviposit in the roots in August, 

 many eggs being laid together. The gall (.-1. mdicis) breaks 

 through the swollen root in September, but in October gall 

 growth ceases until the following spring. The flies then mature in 

 autumn, and emerge in the spring of the year following, usually in 

 April or May. 



OCCURRENCE IN EPPING FOREST. 



Andricits radicis. Abundant. I found these galls either 

 singly or 5 or 6 together ; in the latter case they appear to form 

 one gall on the root, but on removal they fall apart. They may 

 appear quite above ground, be partially covered with earth or 

 be entirely beneath the soil. They do not always appear on the 

 root, but may grow direct from the trunk, either just above or 

 below the ground. I have sometimes found these galls on the 

 roots of young oak plants grown scarcely a foot high. The 

 insects from the A. trilineatus galls seem to prefer ovipositing at 

 some place on the root where an A. radicis gall has previously 

 grown, so that old dried-up and woody galls of A. radicis may 

 often be found near the fresh specimens. 



