B OA RMID.-E—BIS TON. 1 3 3 



resembling a birch twig ; purplish-slate, dull purple, purplish- 

 chocolate dusted with white ; yellowisli-browu, dull green, or 

 brownish-green ; the budlike lateral projections on the ninth 

 segment generally paler, but sometimes darker ; the small 

 dorsal eminences on the twelfth segment often ochreous ; 

 frequently there is a row of pale subdorsal spots. In the 

 green varieties each segment is transversely shaded with 

 reddish ; undersurface irregularly and faintly streaked with 

 dull orange, in some examples having orange ventral dia- 

 monds ; spiracles bright brownish-red, often with ochreous 

 blotches immediately above them. (C. Fenn.) 



July to September on birch, oak, sallow, blackthorn, plum, 

 elm, rose, beech, apple, pear, alder, willow, poplar, sycamore, 

 bramble and currant ; feeding at night. When full grown 

 rather sluggish, if blown or shaken out of a tree, lying for a 

 considerable time as if dead. 



This larva has been extensively experimented upon by 

 Professor Poulton as to the connection between its colour and 

 its surroundings. He seems to have conclusively proved that 

 the former is directly influenced by the latter, even to the 

 extent of showing that an actual change in the colour of a 

 larva is produced after its complete seclusion to darker or 

 lighter surroundings, and in accordance therewith, even in 

 so short a period as eight days. Very full details may be 

 found in the " Proceedings of the Entomological Society of 

 London " for 1892. On the other hand, the influences, what- 

 ever they may be, which are at work causing blackness in 

 the moth, have apparently no similar eft'ect upon the larva, 

 since Mr. Porritt tells me that in his own neighbourhood, the 

 nursery, or focus, of the black range of variation, the larvee 

 of this species are of a remarkably pale green ! 



Pupa robust, stoutest in the middle, tapering ofi" very 

 regularly to the tail ; head not prominent, limbs closely 

 packed, and the antennae not strongly cross-ribbed ; wing- 

 covers sculptured with very shallow, faint, incised, irregular 



