ADAPTATION 193 



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Arctia caja. In this species the markings are well known to 

 be liable to great variation. As Barrett says, even in nature 

 individuals are rarely quite alike, and an immense number of 

 strange forms occur in collections. 5 These are greatly sought 

 after by some collectors, especially in England, where they fetch 

 high prices at auctions, and it is notorious that most of them come 

 from Lancashire and the West Riding of Yorkshire. It is com- 

 monly supposed that the breeders of that district subject them to 

 abnormal conditions, and especially to unnatural feeding, but 

 I know no clear evidence that this is true. From whatever cause 

 it is certain that the natural pattern is, in some strains at all 

 events, very easily disturbed. 



The elaborate experiments of Schroder with Abraxas grossu- 

 lariata are difficult to follow and are complicated by the fact 

 that the series which was submitted to abnormal temperatures 

 was derived from an abnormal original pair. From the evidence 

 given it is not clear to me whether the temperature had a distinct 

 effect. This insect, like Arctia caja, produces an immense number 

 of variations (especially in the amount of the black pigment) 

 and as most of these are, I believe, reared in domestication for 

 sale, it is highly probable that the species is easily influenced 

 by cultural conditions. 



Schroder describes two other experiments which have been 

 accepted by Semon and other supporters of the view that acquired 

 characters are transmitted. In the first, Phratora vitellinae, a 

 phytophagous beetle living on the undersides of leaves, was used. 

 It naturally feeds on Salix fragilis, a species without a felt, or 

 tomentum, on the underside of the leaves. Larvae were trans- 

 ferred to another willow (near S. mminalis] which has the under- 

 sides of the leaves felted. The larvae took readily to the new 

 food, pushing the tomentum before them as they gnawed the 

 leaves. They came to maturity and when they were about to 

 lay their eggs they were given a free choice between S. fragilis 

 and the tomentose species. The greater number of ovipositions, 



r 



5 For illustrations see Oberthur's Etudes d'Entom., 1896, where many of these 

 curious aberrations are represented; also Barrett, Lepid. Brit. Islands, II, pp. 71 

 and 72. 



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