between lepidopterous larv/e and their surroundings. 357 



experiments, undertaken in order to attempt to ascertain 

 the susceptible stages of this highly-vSensitive larva. 



The experiment started on May 10th, when the young 

 larvse were first fed upon the leaves of Fop^dus nigra, all 

 dark twigs and branches being at first rigidly excluded. 

 It must be remarked, however, that for a few days after 

 ]&ay 10th the leaves had only just expanded and were 

 somewhat brownish. Various sets of larvae were withdrawn 

 from the stock, and the transference experiments were then 

 conducted in the following manner. All measurements 

 were taken when the larvse were stretched and straight. 

 A convenient summary of the results of the following 

 experiments will be found in the table on page 319. 



A. A. hetularia. 



May l&h. Twenty hetularia larvae at the end of the 1st 

 stage, and nearly all changing the first skin, and 5*0 mm. 

 long, were transferred from green to black surroundings 

 (the twigs of the Turkish oak). Up to this date the green 

 leaves of P. nigra upon which they had been placed on 

 May 10th were somewhat brownish, because the buds had 

 only just opened. 



3fay 20th. The larvffi were examined from time to time 

 between the 16tli and this date, and had always been found 

 upon the leaves and never upon the twigs. On the 20th 

 every single larva was found upon the leaves. They even 

 avoided the stem of the food-plant. Ten larvae changing 

 the 2nd skin, and 8 "5 mm. long, were re-transferred into 

 green surroundings (A^). The 10 remaining larv* had 

 attained various degrees of development in the 2nd stage, 

 3 being at the end of it, but not yet changing the 2nd 

 skin. From this date to the 29th these 10 larvae were fed 

 upon Balsam Poplar, but from the latter date onwards 

 upon F. nigra. 



May 25th. Only 1 on the twigs, the rest on the leaves. 

 One larva was changing the 2nd skin, and none had yet 

 entered the 3rd stage. 



May 29th. Two larvae on the twigs, and both these 

 were changing the 8rd skin. Of the rest 1 was cho.nging 

 the 3rd skin and 125 mm. long, and 2 had just changed 

 it. These 5 were re-transferred to green surroundings 

 (A-). The remaining 5 were in the 3rd stage, 4 nearly at 

 the end of it, and 1 very small. 



May Vyl st. Only 1 on twigs. Four changing 3rd skin, 



