399 



much darker and richer, than the males of those fed on whitethorn. 

 The elm-fed females were not so large as those of the hawthorn-fed 

 larvfe ; and most of them were crippled and imperfectly developed. 

 There were also many of the whitethorn-fed females crippled ; and 

 the whole experiment went to show that had the species depended 

 solely on the existence of either elm-fed or whitethorn-fed indi- 

 viduals, it would probably have soon degenerated or become 

 extinct.* Further experiments on this point, carefully conducted, 

 are much needed; and it is just the inquiry for the local ento- 

 mologist to take in hand, rearing from year to year successive 

 broods of the same species, feeding the larvae upon such different 

 plants as they can be got to eat, taking care to preserve all other 

 conditions the same, and then from time to time noting down the 

 results. + 



Cases of variation, however, and to a great extent, have been 

 known to occur in some species of moths among specimens reared 

 from the eggs of one parent, even when all were fed upon the same 

 food. Mr. MacLachan mentions that of the Sterrlm sacraria, L., 

 in his paper above alluded to on the variation of the Lepidoptera. 

 He has there described and figured a series of varieties of this moth 

 so remarkably different from each other, that had they been taken 

 separately on the wing, instead of having been brought up by the 

 hand, it is not likely that any one of them would have been referred 

 to the species from which the eggs had been obtained. And this 

 fact leads him to think that several supposed foreign species which 

 he notices are in like manner all one and the same, and identical 

 with the S. sacraria of this country, from which the above varieties 

 were derived. J 



* See Ent. Trans., 3rd Ser., vol. v., Proceed., p. xliv. Id., vol. i., Proceed., p. 15. 

 t Other experiments might be made in reference to the influence of the 

 various rays of light upon the larvae of butterflies and moths. See a case 

 mentioned in the " Zoologist " (vol. ui., p. 1198), in which several caterpillars 

 of the peacock butterfly (Vanessa ioj were confined in difi'erent boxes covered 

 with glass of difi'erent colours. This treatment seems to have afiected the 

 development and colours of the imago. Some that were kept whoUy in the 

 dark produced butterfiies in general larger than the others, and their colours 

 brighter. Other results are recorded, though not very decisive ones. 

 X Ent. Trans. 3rd ser., vol. ii., p. 463., pi. xxiii. 



