346 Mr. 'Ponlton's farther experiments upon 



3. Dark Surroundings near the Larvce, hut not actually 

 in contact. 



Experiment X. 

 X. 



Cylinder: Hfitiht, IdO mm. ; interin. diam., 2(i-5 mm.. ; approx. 

 capacity, 110 cc. 



In this tall narrow cylinder only green leaves and shoots of food-plant 

 were present, but outside it many twigs, as in I., were placed. 



July 10. — 12 young larvfe intro- 

 duced from the " first stock." 



July 25. — Length about 24-0 mm. 

 4 green, 2 intermediate, (i brown. 



Aug. 1. — All but 1 in last stage ; 

 3 gi'een (1 changing last skin), 

 2 greenish intermediate, 2 light 

 hroum, 5 dark broivn. 



Aug. .5. — All in last stage ; 3 green 

 (rather dull) , 2 greenish interinediate, 

 1 verg light brown, 1 very light grey, 

 4 deep brown (1 very dark, 1 dead), 

 1 very dark blackish grey. 



The criticism made on the analogous experiment with 

 the 1889 larvae (see p. 334) holds in this case. The 

 effect of crowding comes out so clearly in some of the 

 green surroundings (see Experiments XII. and XIII.), 

 that it will be necessary to repeat this experiment, in- 

 cluding very few larvae in each cylinder, and making 

 comparison experiments with the light dimmed by 

 objects other than dark twigs. UntiHhis is done, there 

 will be no reason for believing that a larva is affected 

 by any twigs except those with which it is in contact, 

 or at any rate immediately surrounded. It would be 

 interesting also to make use of dark cylinders enclosed 

 in glass tubes of varying thickness. 



B. Green Surroundings. 

 1. Green Surroundings ichich are natural to the Larvce. 



{See Table, 2mge Ml.) 



The strong susceptibility to green surroundings in the 

 absence of darker colours is very clearly brought out in 

 these experiments, but also the much greater suscepti- 

 bility to brown, so that when the larvas were crowded, as 

 they were in XII. and XIII., in cases with only half the 

 capacity of XI. and XIV., they were strongly affected by 

 one another's colours, which arc always brown in the 

 earlier stages. The light brown larvae thus produced 

 much resembled those from Experiment VI., one of 

 which is shown in Plate XIV., fig. 14. 



