THE GALL-FLY. 129 
oak-apple are nearly as beautiful though not so brilliant. 
Yet the oak possesses no such storehouse of colour as is 
popularly attributed to the rose. Its leaves are simple 
green, and its flowerets are so colourless as scarcely to be 
distinguished by the unassisted eye. 
Whence then are derived these beautiful colours? 
Some hasty observers, who have neglected the first rule 
of logic, and drawn an universal conclusion from par- 
ticular premises, have said that the colours of the gall 
are derived from the insect; adducing, as a proof of 
their assertion, the brilliant colours which equally deck 
the rose-bedeguar and the Cynips rose from which it 
sprang. But if they had only followed the example of 
careful naturalists, who, like Dr. Hammerschmidt, have 
examined and drawn between two and three hundred 
species of galls, so hasty a generalisation would never 
have been made. ‘The cherry or leaf-gall of the oak is 
every whit as gorgeously coloured as the bedeguar of the 
rose, while the insect that made it is quite black. It is 
true that the diaphanous wings glitter as if they were 
made of polished gems; but this appearance is due, not 
to the wings themselves, but to the myriad hairs with 
which they are regularly studded, each hair acting as a 
miniature prism by which the light is refracted and 
broken into the resplendent hues of the rainbow. 
Many other trees beside the oak are chosen by certain 
species of gall-fly, and even the herbs and flowers do 
not escape the ravages of these remarkable insects. The 
white poppy, from which is obtained the opium of com- 
merce, is attacked by a species of gall-fly, which lays its 
eggs in the large head, or pod, and sometimes does much 
damage to the plant, the delicate divisions between the 
seed vessels being rendered quite hard and solid, and the 
R 
