1886.] Larva of Smerinthus ocellatus and its Food-plants. 147 



healthy than they were upon the unsewn leaves, although they were 

 far from healthy upon the latter during the past year). Nevertheless, 

 I hope to succeed in the rearing the larvae upon such leaves in a more 

 favourable season, and I believe that some deviation from the extreme 

 white variety will result (this conclusion being warranted by the results 

 of other experiments described in the present paper). Nos. 1 — 4 were 

 not represented in the other two series. 



Crab (No. 5) produced white varieties, as far as could be ascertained, 

 acting as it did on the present larvae and in Series I (No. 1). It was 

 quite as fatal in its effects as ordinary apple, and the larvae seem to 

 grow more slowly when fed upon it than upon any other plant, as was 

 also noticed in the case of the parent larvae. Considering the extreme 

 effects following the use of this food in the other cases, it could hardly 

 be expected that there would be any appreciable difference in the 

 larvae of this series. 



Salix viminalis (Nos. 6 and 7) produced exactly the same effects as 

 in the parent larvae, while the larvae of Series II (No 1) fed upon the 

 same plant were fairly strong white varieties. This is a very strange 

 contrast considering the parentage of the two series, but the un- 

 certainty of the male parent in Series II prevents much importance 

 from being attached to it. 



The effect of viminalis, sewn so as to show the under sides of 

 the leaves (No. 8), affords a most interesting comparison with the 

 results of Nos. 6 and 7, for the former produced a strong white 

 variety (that is up to the time of its death). Here is a distinct proof 

 of the effect of the colour of one leaf -surface as apart from the leaf- 

 substance eaten by the larva. 



Salix alba (No. 9) cannot be compared with any previous experience 

 of my own. I expected it to act like 8. viminalis, but the iarva was 

 rather yellower than those which had fed upon the latter plant. The 

 leaves of S. alba vary much in whiteness, the young leaves being far 

 more downy and white than the older ones, so that a different effect 

 is probably produced by the two kinds. There is independent evidence 

 (Mr. Boscher's, which will be alluded to presently) that this food- 

 plant produces white larvae. 



Salix Smithiana (No. 10) produced a larva which when mature was 

 on the whitish side of intermediate. This is probably the normal 

 result of the food Avhich in this case coincided with the hereditary 

 influence. In Series II (No. 2), however, the larvae fed upon the same 

 food-plant were rather yellower; hence the effects of 8. Smithiana 

 and S. viminalis in the two series were the exact converse of each 

 other — a very perplexing result. At the same time, as already 

 pointed out, there was nothing at all unusual in the results of any of 

 the individual sets of experiments. (See also the notes upon the 

 parentage of the larvae of these two series.) 



