QUADRIFID&. 255 



grey, with a large black spot in the middle of each segment ; 

 legs pale brown; prolegs pale grey, the anal pair much 

 extended, but when at rest laid closely together and slightly 

 elevated. When quite full grown the markings become 

 much obscured or obliterated and the colour paler. In 

 general appearance singularly like the lame of some of the 

 larger Geomctridcr. 



By careful and continued experiments on larvae of this 

 species from the egg to full growth Professor Poulton and 

 Miss Lilian Gould have proved, I think conclusively, that 

 the shades of colour, from pale grey to uniform dark brown, 

 are controlled by their surroundings, so as to agree in the 

 most favourable manner, for their own security, with the 

 colour of the twigs and branches upon which they rest. 

 Papers on this subject have been read before the Entomo- 

 logical Society of London. 



April to July on willow, but occasionally upon poplar and 

 plum; feeding at night; hiding in the daytime in the 

 crevices of the bark of the tree, on which, from their 

 wonderful assimilation in colour and structure, they are 

 practically invisible, and are best found by the sense of 

 touch. 



In the egg state through the winter. 



Pupa of the usual Noctua form, regularly tapering behind ; 

 the face and antenna-covers tolerably smooth, but the limb- and 

 wing-covers closely inscribed with sculpture of incised lines, 

 and the dorsal and abdominal segments with abundant pitting, 

 except a smooth band at the hinder edge of each segment, 

 All this sculpture is obscured by a thick dusting of bluish- 

 white powder or bloom, which clings closely to it; under 

 this the general colour is purple-brown; cremaster black, 

 short, broad, flattened and extremely rugose, furnished with 

 a pair of strong spines slightly hooked, and outside these 

 with a few light brown curled bristles, with all of which it 

 holds strongly to the silk of its cocoon. This last is open 



