140 THE OAK GALLS AND GALL INSECTS 



(i.) Sexual Generation. Ia. Neuroterus baccarum (Linn.) 

 Inquilines. Syneygus facialis {Htg.) S. radiatus (Mayr.) S.albipes 

 (Htg.) 



Gall. 



Grows through the leaf or appears on the $ catkin. Colour : 

 Yellowish green, green and red or entirely red. Shape : 

 Globular. Soft and sappy. (Diameter y^ mm.) 



Imago. 



Colour : Black. Antennce : Brownish, 2-5 basal joints yellow ; in the 



^ 15-jointed, in the o 14-jointed. Thorax: Dull and rou^^h ; scutellum 



wrinkled. Abdomen: Distinctly pedunculate. Ovipositor: Short. Legs: 



Yellow, coxae entirely black or only at the base. IViiigs : Hyaline, broader 



towards the apex, longer than the body ; first cubital cellule clouded. 



Account of Generation Cycle. 



The Neuroterus lenticularis galls fall to the ground in September 

 and October, dampness being necessary to enable them to reach 

 maturity. They may be found in the winter in a swollen 

 condition, either separated from, or still adhering to, the leaf. 



The insects emerge from these galls in April and sometimes 

 in May. This is the asexual brood, comprising females only, and 

 these immediately proceed to lay their eggs in the oak buds. 

 The resulting galls, N . baccarum, appear in May or the beginning 

 of June, the insects emerging from them at about the middle of 

 the month. The reason for this rapid maturity is to be found in 

 the soft and sappy condition of the galls, which are liable soon 

 to dry up. This being the sexual generation, oviposition takes 

 place only after copulation, and the eggs are laid in the backs of 

 the leaves at about the end of June. In three weeks galls appear 

 on the under-surface of the leaves. These are N. lenticularis galls. 



Unless parasitised, the N. baccarum galls shrivel up soon after 

 the insects have emerged ; these insects only lay their eggs on 

 the young and tender leaves. 



OCCURRENCE IN EPPING FOREST. 

 I found Neuroterus lenticularis galls very common. First 

 appearance noted, July 19th. Neuroterus baccarum. Abundant. 

 Leaf and catkin galls both plentiful. In many cases I found 

 two or three galls amalgamated. First appearance noted 

 May loth. 



(2.) Agamic Generation. II. Neuroterus laeviusculis 

 (Schenck). Inquilines. Synergus tscheki (Alayr.) 



