298 Mr. E. B. Poulton. Essential Nature of the [Apr. 23, 



15. Experiments upon the Larvce of S. Ocellatus. 



The variability of this species must have been observed by many 

 entomologists. In Mr. Meldola's editorial notes there are the follow- 

 ing references to this larva : — In 1879 Mr. E. Boscher found ten to 

 twelve larvao npon Salix Viminalis near Twickenham. These larvae 

 were of a bright yellowish-green ground colour, and all possessed the 

 rows of red- brown spots which sometimes occur on this species. He 

 also found eighteen to twenty larvae of the same species feeding upon 

 8. Triandra, in a locality not far distant, all of which were dull 

 whitish-green above, passing into bluish-green below. None of 

 these latter were spotted. In 1880 Mr. E. Boscher found seven larvae 

 on 8. Viminalis in the same locality, similar to those found upon this 

 plant the year before. He also found six larvae upon another species 

 of Salix in the same osier bed, two being of the bluish-green and four 

 of the bright green variety. 



It must be well known to all collectors that the bluish-green form 

 occurs on ordinary apple trees in gardens. In 1880 Mr. Boscher con- 

 ducted some breeding experiments upon this larva at Mr. Meldola's 

 suggestion. The larvae from three batches of eggs were fed upon 

 S. Triandra, 8. Viminalis, and apple respectively. Only three of the 

 third batch survived, and were all of the bluish-green form. 



I have added the following evidence to the case of 8. Ocellatus 

 (" Trans. Ent. Soc. of London," Part I, April, 1884). Salix Rubra 

 and S. Ginerea produce the bright green variety, and crab also (as far 

 as I could remember). On the other hand my experience had been 

 that 8. Viminalis produces whitish-green varieties. Figures of the 

 two varieties are given in my paper. It must not be supposed that 

 the yellowish-green varieties are always spotted, or even commonly 

 so, but I believe that an instance of a spotted bluish-green variety 

 has not been hitherto recorded. 



My own experiments upon this species were conducted during the 

 summer of 1884. The eggs were obtained from Mr. W. Davis, of 

 Dartford. The larvas after hatching were divided into five lots of six 

 each, and they were fed upon the following food-plants : — apple, crab, 

 Salix Viminalis, S. Ginerea, S. Rubra. As I was travelling at the 

 time, it was sometimes difficult to obtain the right plants. On such 

 occasions I made use of a plant which I believed (from an examina- 

 tion of its leaves) would produce the same colour as the one I had 

 started with. The only instances of this were — once or twice in the 

 case of crab, when I substituted an apple with similar leaves (green 

 and glabrous underneath), and in the case of 8. Rubra, for which 

 8. Babylonica was given once or twice and 8. Triandra once. I had 

 previously ascertained (in the summer of 1883) that no effect is pro- 

 duced by feeding a larva for several days upon a food-plant which 



