204 A BOOK OF INSECTS 



the most surprising fact of the whole amazing story — they 

 are by no means exempt from the duties of maternity. 

 Each female flies confidently to her old foster-mother the 

 oak tree, and by means of the long ovipositor with which 

 she is equipped, thrusts her eggs into the very heart of a 

 bud, right down among the embryo leaves and catkins. 



In the case of an ordinary insect, the life-cycle would 

 end with the egg-laying of the adult. To continue our 

 observations would merely be to verify facts which we 

 had already noted. Not so, however, with these gall- 

 wasps. One can never be quite sure that their life-history 

 is complete until one actually traces it through to a 

 repetition. Let us therefore observe the unfolding of an 

 oak bud in which the spangle gall-wasp has laid her eggs. 

 We shall find that galls are produced upon the catkins as 

 well as upon the leaves ; but they are not in the least like 

 spangle galls. In size and appearance they resemble so 

 many currants — at first green, but mellowing under the 

 influence of sunlight to a ripe crimson. The sight of 

 these galls comes as a severe blow to our cut and dried 

 theory that like invariably produces like ; for the lineal 

 descendants of spangle galls have produced currant galls, 

 and this is their invariable custom. Moreover, when in 

 due course the second generation appears in May, we find 

 that it comprises both males and females, and that the 

 insects are quite different from those of the agamic brood. 

 Notably, the females lack long ovipositors — implements 

 which would be superfluous, because these summer gall- 

 wasps lay their eggs beneath the cuticle of the leaf, and 

 have no tightly packed buds to deal with. These insects, 

 in fact, give rise to a new generation of spangle galls ; 

 and so this wonderful alternation of generation — this 

 interchange of personality — continues year after year. 

 These facts were not known to the early naturalists, who 



