1885.] Colouring of Phytophagous Larva?. 303 



ference in consequence of the change of food. The small la.rva (in 

 the third stage) found upon the same plant, on the same date, was 

 also fed at once upon apple. At this early stage the larva was as 

 bright a specimen of the yellowish-green variety as I have ever seen. 

 The apple made no difference in its colour, although it was eaten for 

 many days. The larva had been slightly injured, and died without 

 entering another stage. Evidently it possessed an even stronger 

 tendency towards the yellowish -green variety than my bred speci- 

 mens showed towards the other form, since the colours were very 

 marked, while the larva was so small. 



The two whitish larvae in the fourth stage, found on August 11th, 

 on Salix Ferruginea, were fed upon 8. Triandra or 8. Rubra during 

 the whole of the fifth stage. On August 24th these larva? were adult 

 (and one of them browned) : some slight effect had been produced, 

 for they were both of them less white than was to be expected from 

 their appearance when found. 



The seven larvae found August 17th and 18th upon 8. Bahylonica, 

 were fed upon the same food-plant, and carefully compared. The 

 bright yellowish one, which was more advanced than the others, 

 became adult (and turned brownish) August 25th. It remained much 

 the brightest all through. The others became adult a few days later, 

 and throughout remained intermediate forms with a variable tendency 

 towards the yellowish variety. 



The tendency of the food- plant was seen during the growth of 

 these six larvae in the fifth stage, for they were whitish interme- 

 diate varieties at the beginning of this stage, and they inclined the 

 other way at its close. The other larvae were too old for experiment. 



18. The Protective Character of the Variation in the Larva? of 

 S. Ocellatus. 



These larvae are protected by resembling the colour, and, to some 

 extent, the veining of the underside of the leaves of their food-plants. 

 The relations between the ground colour of the larvae and the under- 

 sides of the leaves are shown in the following table, as far as these 

 data have been indicated by any observation or experiment hitherto 

 recorded : — 



Food-plant. 



Effect on S. Ocellatus. 



Colour of undersides 

 of leaves. 





Strongly tends towards whitish varieties 

 according to all observers, and also 

 proved by two sets of experiments 

 (Mr. E. Boscher's, quoted by Mr. 

 Meldola, and my own). Exceptions 

 very rare, and only known in 1884. 



White undersides | 

 pubescent. 







