140 



The GaUs of Essex : a Contribution to a 



Fig. 32. Biorhiza renum. 



numbers on a leaf, but eacii gall 

 is single-celled. The galls are 

 mature and fall from the leaf in 

 autumn ; the gall-flies emerge 

 therefrom in June. Biorhiza 

 RENUM, Hartig (Fig. 32) [aga- 

 mous form of Trigonaspis me- 

 gaptera] . 



QuERcus EoBUR, L. Leaf. 

 Early in the year some oak 

 leaves are occasionally noticed 

 to curl up and become consi- 

 derably shortened ; if examined 

 it will be noticed they have a 

 spherical, smooth, green, pea- 

 sized swelling at their base; 

 frequently the whole leaf is 

 galled, and two, three or more 

 galls are confluent. In section 

 this succulent gall exhibits a 

 moderately thin walled cavity, 

 which contains two thin, small, 

 brown, cocoon-like larva-cells, 

 separated by a very thin sep- 

 tum. Certain specimens of this 

 gall might be taken for a bud- 

 gall, but if closely examined the 

 midrib of the leaf is generally 



noticeable. The galls are mature in spring or early 

 summer, and do not fall from the twig ; the gall-flies 

 emerge therefrom in June or July. Andricus curvator, 

 Hartig. (Fig. 33.) 



Quercus Eobur, L. Leaf. The common cherry-gall of 

 the oak is a succulent, spherical, smooth, green or rosy 

 gall, of about the size of a cherry ; it occurs on the 

 under side of the oak leaf, generally singly, but sometimes 

 three to five are found on one leaf. It is single-celled, 

 gathered before mature the gall shrivels considerably ; 



Fig. 33. Andncua curi'iitor. 



