SESSILE-FRUITED OAK. 



287 



remaining groups of the Lepidoptera there are a vast num- 

 ber of Oak-eating species ; we must, however, limit our no- 

 tice to one whose devastations are sometimes so extensive 

 as completely to denude Oak woods of their foliage through- 

 out entire districts : this is the work of the leaf-rolling cater- 

 pillar of the pretty little green-coloured moth, the Tortrix 

 mridana, which, in some years, appears in countless my- 

 riads. Providentially, these visitations rarely, if ever, 

 continue for more than two seasons successively, other- 

 wise the trees would inevitably perish from the renewed 

 deprivation of their leaves, members so essential to their 

 very existence. How the sudden diminution is effected 

 we can only guess at, but, in all probability it is by that 

 beautiful ordination of providence, where a corresponding 

 increase of those parasitic and other enemies takes place 

 of which it is the accustomed and peculiar prey. 



Several coleopterous insects in the perfect state also feed 

 upon the leaves of the Oak ; among them is the well-known 

 cockchafer (Melohntha vulgaris), the Orchestes quercus, 

 or Oak flea, the Cryptorynchus quercus, Agrilus viridis, 

 SfC. They are also infested by a species of Psylla, by 

 Aphis roboris, and A. quercus, Coccus quercus, fyc, and 

 we may here state our belief, deduced from long ob- 

 servation, that the honey dew upon the Oak is invariably 

 the produce of these insects, as we have never been able 

 to trace its presence, except where some of the species 

 were to be detected upon the tree. 



Of the various galls or Oak apples, the nidi of different 

 species of cynips, produced by the puncture of the ovi- 

 positor of the female upon the different parts where they 

 are found, we shall only mention that, in regard to those 

 beautiful little excrescences so common upon the under 

 side of the leaves of the oak and known by the name 



