220 Lilian J. Gould's experiments 



bark, and changed for freshly prepared ones whenever 

 they became yellowish or discoloured by drying. 



At first all three sets were fed on willow {Salix 

 vitellina) from the same tree, but after a time, having dis- 

 covered a kind of willow with whitish silvery leaves {S. 

 regalis), I fed the tbird set (those with white sticks) with 

 the white willow also, in order to see if any difference of 

 shade would be produced between these and the larvfe 

 on green willow without sticks. The larvae of C. nupta 

 being rather large, it was necessary to have a great 

 number of cylinders, to avoid overcrowding. The larvae 

 with dark surroundings were placed in cylinders 7 and 

 12, the larva) with green surroundings in cylinders 3, 8, 

 and 10, and those with white surroundings in cylinders 

 11 and 16. 



As the hatching-out had extended over a period of 

 nearly four weeks, it was necessary to divide the larva) 

 as nearly as possible according to age, so as to render 

 observations as to times of ecdysis, &c., easier and loss 

 liable to error. The experiments with C. nupta were not 

 as satisfactory as those made with other species, as the 

 larv^ were never so healthy, and very many died when 

 nearly full-fed, from some cause which I could not dis- 

 cover. 



The following notes refer to larvfe with dark sur- 

 roundings : — 



Cylinder 7. — June 17th. — Six larvae hatched, and 

 were placed in cylinder 7. The newly-hatched larva) 

 measured not quite 6 mm., and their colour was uniform 

 dark brown. They were fed on Salix vitellina, the 

 darkest green leaves being selected, and given on the 

 twig. 



June 20tli. — The first ecdysis occurred, with no change 

 of colour. 



June 30th. — I gave black sticks of the same kind as 

 those used for 11. cratagata in previous experiments. 

 Later in the day the second ecdysis took place. 



July 1st. — The larvse began to darken perceptibly, and 

 the adjustment of colour gradually increased in perfection 

 during this and the succeeding stage. 



July 9th. — The third ecdysis occurred. The larvae 

 were all distinctly brown, and darker than any of those 

 with other surroundings. 



July 18th. — The fourth ecdysis took place. 



