BUTTERFLY FLIGHT 169 



movement is when they mount across the high folds of the 

 boughs, sweeping in and out of the knolls and depressions 

 of the foliage as a swallow skims over the undulating 

 mustard blossom in the downs. So the proud game of flying 

 goes on through all the hot hours in the July woods ; and 

 the peculiar relation of the butterfly's flight to the lines of its 

 favourite tree seems gradually to shape the tree before our 

 eyes, like a fine piece of sculpture, and adds beauty to the 

 oak as to its owner. 



Purple emperors are not bred on oaks, as are the little 

 purple hairstreaks which play at being purple emperors in 

 the same weeks. The eggs are laid, and the caterpillars live 

 for nearly a year on the sallows, which in many damp and 

 clayey oak woods lift their brittle and lowly boughs among 

 the undergrowth. Nor when the butterflies emerge do they 

 always set their thrones upon an oak ; a chestnut is fairly 

 often chosen, and occasionally some other tree. But usually 

 it is the king of trees that is chosen by this royal butterfly, 

 and there seems a natural fitness in the choice. The brilliant 

 bluish-purple gloss is a prismatic or iridescent colour, and 

 at certain angles the wings appear dark brown, though finely 

 decorated with the white bands and splashes. The empress, 

 though larger, has no such gloss ; she is not a brilliant 

 butterfly, though she is a distinguished one with her large 

 contrasted markings. Nor does she sport in flight about 

 the oaks with the males' activity ; she rests much longer 

 on her perch, which is sometimes much closer to the ground. 

 In dull weather she may sometimes be found almost torpid 

 on some branch at the edge of a wood or woodland ride. 

 The taste of these royal butterflies for carrion is almost 

 a classical example of a lapse from magnanimity, but it is 

 not so fixed a weakness as is often supposed. When they 

 come to the gamekeeper's gibbet, or settle upon filth on the 



