GEOMETRIDiE. 99 



middle of the back darker green edged with white ; two thin 

 white lines on each side, and a whitish stripe along the spiracles. 

 When mature it burrows into decayed bark or wood (virgin 

 cork in confinement), and before changing to a reddish-brown 

 chrysalis, it spins a thin covering of silk and woody particles over 

 the mouth of the chamber. The caterpillar and the chrysalis 

 are shown on Plate 39, Figs. 2 and la. Although the bulk 

 of the moths emerge the following April, some have been known 

 to remain until the following or even the third year. The males 

 fly about aspen, but only in the sunshine ; in other respects its 

 habits are pretty much those of the last species. 



The distribution of the species in England seems confined to 

 two areas : a western one represented by Worcester, Gloucester, 

 with Monmouth, Wales, Wilts, and Dorset ; and an eastern 

 one by Norfolk, Cambridgeshire, Suffolk, Essex, Middlesex, 

 Kent, Surrey, and Sussex. In Scotland only recorded from 

 Moray. 



The range abroad extends to Amurland. 



GEOMETRIDtE. 



Caterpillars of this family of moths, with very few exceptions, 

 have only two pairs of claspers or prolegs ; when there are more 

 than four claspers, the extra ones are only rudimentary and 

 therefore useless. In moving from place to place the caterpillar 

 stretches out to its full length, first to one side and then to the 

 other, as though measuring the distance. When a hold is 

 secured with the true legs the body is arched and the claspers 

 are brought up almost to the point held by the true legs ; the 

 latter are then thrust forward and the measuring business pro- 

 ceeds as before. Some kinds perform the looping manoeuvre 

 very deliberately, but others at a quick rate. In common par- 

 lance among British entomologists the caterpillars are called 



