Miss E. Bridges upon lepidopterous larvae, and pupae. 137 



that the larvae are only influenced by the colour of the 

 twigs on which they rest, or of those quite close to them, 

 and in the experiments here recorded, all were kept alike 

 in clear glass cases with white roof and floor, the only 

 difference being in the colour of the few sticks placed 

 among the leaves of the food-plant. 



The eggs, about 130 in number, were all laid by the 

 same moth, and hatched between August 14 and 16, 1909. 

 They were introduced into the different environments 

 within a few hours of hatching. The environments were 

 as follows : — 



A. Slips of white wood painted crimson with water- 

 colour. 



B. Black twigs of birch. 



C. Slips of white wood. (The wood not a dead white, 

 but the cream colour of common deal.) 



D. White wood painted a pale green with water- 

 colour. 



E. Dead sticks of oak covered with grey lichen and 

 green powdery alga. 



The food-plant employed was elder (Sambucus nigra). 

 The larvae proved to have only various shades of black, 

 brown and cream at their command. On the pale green 

 sticks (D), they became cream-coloured, on the red (A), a 

 reddish-brown ; on the lichen-covered sticks (E) no lichen- 

 like markings appeared as in the experiment on bidentata 

 (see p. 144), but the larvae became a rich black of the 

 same colour as the bark, and were most inconspicuous. 

 Their sensitiveness showed itself rather in the swiftness 

 and completeness with which they adapted themselves to 

 the black and white environments (B and C). On the 

 first day (August 21) that any were noticed on the black 

 sticks, four became black on the back (they were distinctly 

 darker than any of the other sets), and three days after 

 this all but two were completely adapted, i. e. were indis- 

 tinguishable in colour from the sticks. Those on the 

 Avhite sticks took some time to get rid of all traces of 

 their dark markings : the first signs of the " bleached " 

 appearance were not noticed until 12 days after they 

 began to use the sticks (September 2) : all but one were 

 adapted in 21 days (on September 11). Notes were taken 

 every three days with the exception of the first week. 

 Those between September 29 and October 11 are omitted 

 as no change was then recorded. 



