196 HALF-HOUKS IN THE GREEN LANES. 



same parent are quite dissimilar in appearance. 

 Indeed, it was not until the last few years that 

 they were regarded as different species. The two 

 kinds of disc-shaped galls common on the under 

 surface of oak-leaves are frequently a puzzle to 

 people ignorant of natural history. In Fig. 139 

 the upper portion of the leaf represents those 

 commonly known as "oak spangles," whilst the 

 lower portion is seen bearing those which go by 



Fig. 138. 



Gall Insect (C'jnips sp). 



the name of " button galls." The former are due 

 to an insect called by entomologists Cynips longi- 

 pennis, of which we give a magnified figure. The 

 " button galls " are caused by another insect known 

 as Neurobius Reaumuri. Besides these two, there 

 are at least half a score other species of nearly allied 

 insects whose attacks produce similar malformations 

 of the cuticles of leaves of various kinds of oaks. 

 The sections of these "spangles" and "buttons' 



