OF EPPING FOREST. 167 



Imago. 



\'ery variable, not distinguishable from A. qiiadrilineattis. 



The A. alhopunctata galls may become wrinkled when old, and 

 in some cases they adhere to the bud axis. They appear at the 

 end of April ; mature very quickly, falling to the ground in May, 

 and occasionally not until Jime. The flies emerge in the 

 following spring, or sometimes not until April of the second 

 year. The eggs are laid in the buds about the middle of ApriL 



OCCURRENCE IN EPPING EOREST. 



Fairly common, but not so much so as in many places. They 

 have very much the appearance of buds, and on this account may 

 be easily passed over without notice. First appearance noted,. 

 April 29th. 



Genus BIORHIZA {West7vood). 



The two generations of this genus are exceedingly alike, and, 

 in some cases, could scarcely be differentiated, except that in 

 the sexual forms, the male is never apterous or with the wings, 

 rudimentary, and the female is usually furnished with wings, 

 though sometimes these may be absent, or only present in a 

 partially developed state. 



The colour in both forms is yellowish brown. 



There is, so far as we know, only one European species, 

 Biorhiza aptera-tevminalis (Fab.) 



The great resemblance which exists between Biovhiza 

 terminalis and B. aptera extends to the ovipositors also, although, 

 as a rule, among the Cynipidae the ovipositors differ even when 

 the other parts are almost, if not quite, identical. The difference 

 between ovipositors is due to the method of oviposition, which 

 varies according to the position in which the e^g is to be laid ; 

 in this case the position of the egg is very different in the two 

 generations, but as the method employed in depositing the egg 

 does not differ, the form of ovipositor remains the same in each 

 case. The great likeness which exists between so many different 

 species of this family is due to want of difference in their mode 

 of life, so that surroundings cannot act upon them to alter their 

 characters, the chief variations occurring in the gall instead. 



This accounts for the similarity in outward appearance 

 between the sexual forms of the genus Dvyophanta and the 

 corresponding forms of the genus Nenroteriis, which were at one 



