202 A BOOK OF INSECTS 



a kind of community, consisting of a number of cells, each 

 containg a larva, the whole mass being clothed with 

 long, red fibres which are probably due to the abortive 

 efforts of the plant cells to produce leaves. Secondly, 

 the species called Rhoditcs eglanterice forms one-chambered 

 galls, about the size of a pea, upon the underside of 

 the leaves ; while the third species, Rhodites nervosus, 

 comes from a gall which is distinguished by thorn-like 

 projections that spring from its surface, like spikes on 

 a mediaeval war club. Almost any hedge in the south 

 of England will supply specimens of these three galls, 

 so that the reader may readily compare them, and breed 

 from them their respective tenants. 



Numerous Cynipid galls are found on the oak. " King 

 Charles's apples " originate in the buds ; " truffle galls " 

 grow from the roots and are sometimes embedded several 

 inches in the soil ; many other species, differing widely in 

 form, spring from the leaves ; while at least two kinds 

 hang like currants from the catkins. All these diverse 

 forms of galls originate in the oviposition of an insect. 

 Apparently the operation of egg-laying is performed 

 in the same manner in every case ; so that we are left 

 to surmise that each kind of gall-larva gnaws the cells in 

 a manner quite different from JLhat adopted by all other 

 kinds. The insect when first hatched is so minute that it 

 can only be watched through the microscope, and the 

 precise manner in which it attacks the cells remains a 

 mystery. Yet it is probable that whereas the plant 

 makes the gall, in so far as the supply of constructive 

 energy is concerned, the tiny grub (or, in certain cases, 

 the developing and enlarging egg), by its peculiar method 

 of irritating the sensitive cells, determines the form which 

 the gall shall take. 



Among the Cynipidcc occurs that remarkable pheno- 



