44 RED AND YELLOW. [introd. 



colour in mice and cygnets 1 ; red and blue in the eggs of many 

 Copepoda 2 , the tibias of Locusts 3 , the hind wings of the Crimson 

 Underwing (Catocala nupta) 4 , &c. Another case of blue as a 

 variety of scarlet is the familiar one of the flower of the Pim- 

 pernel (Anagallis arvensis). Discontinuous colour-variation of 

 this kind is one of the commonest phenomena in nature, but to 

 advance the subject materially it is necessary for a large mass of 

 evidence to be produced. This cannot now be attempted, but in 

 order to bring out the close relation between these facts and the 

 problem of Species I propose to dwell rather longer on one special 

 section of the evidence which must serve to exemplify the rest. 

 The case which I propose to take is that of certain yellow, orange, 

 and red pigments. For brevity I shall present the chief facts in 

 the first instance without comment. 



1. Colias edusa (Clouded Yellow) is usually orange-yellow, having 

 a definite pale yellow female variety, helice, which is not recognized as 

 occurring in the male form. A specimen is figured having the right 

 side helice and the left edusa. Fitch, E. A., Entomologist, 1878, xli. 

 p. 52, PI. fig. 11. This was an authentic specimen, for Mr Fitch tells 

 me that it was taken by his son and seen alive by himself. 



A specimen having one wing white and the rest orange is recorded 

 by Morris, Brit. But., p. 13. 



Intermediates between edusa and helice must be exceedingly rare. 

 Oberthur records two such specimens and says that Staudinger took 

 a similar one at Cadiz. For this intermediate he proposes a new name, 

 helicina. Bull. Soc. Ent. Fr. (5), x. p. cxlv. 



1 In this case I can affirm the alternative character of the inheritance. For 

 several years a pair of swans kept by St John's College, Cambridge^ have produced 

 cygnets, some of which have been of the normal grey, while others have been fawn- 

 colour, a condition which Prof. Newton tells me has been thought characteristic of 

 the "Polish" swan, a putative species. None of these cygnets are intermediate in 

 colour, and all accmire the full white adult plumage, but the feet of the fawn-coloured 

 cygnets remain pale in colour. Now the father of these has pale feet and was 

 doubtless himself a fawn-coloured cygnet ; the hen is normal. The cock formerly 

 belonged to Dr Gifford, who kindly told me that the cygnets of this bird by a different 

 hen were also thus diverse. A pair of these were given to Sir John Gibbons, who 

 informs me that " from these there has been a brood every year, and always I think 

 one of the cygnets has been white or nearly so, the others being of the usual colour." 

 One of Dr Gifford's birds was also given to the late Mrs Gosselin of Blakesware, 

 to whom I am indebted for descriptions of and feathers from several fawn-coloured 

 cygnets which were its offspring. A similar case on the Lake of Geneva is re- 

 corded by Fauvel, Rev. Zool., 1869, p. 334, and another in the Zool. Gardens at 

 Amsterdam, by Newton, Zool. Rec, 1869, p. 99. 



' 2 This is well known to collectors of fresh-water fauna, and I have repeatedly 

 seen the same phenomenon in species of Diaptomus, especially D. asiaticus, in the 

 lakes of W. Siberia. Among thousands of individuals with red-brown egg-sacs, will 

 often occur a few specimens having the egg-sacs of a brilliant turquoise-blue. In 

 this connexion compare the case of the Crayfish (Astacus Jiuviatilis), which turns 

 scarlet on being boiled, and which, like the Lobster, not uncommonly appears in a 

 full blue variety. 



3 Caloptenus spretus with hind tibias blue instead of red, Dodge, Can. Ent., 1878, 

 x. p. 105 ; Melanoplus packardii, having hind tibia? red instead of bluish, Bruner, 

 Can. Ent., 1885, xvn. p. 18. For reference to these observations I am indebted to 

 Cockerell, Ent. , 1889, xxii. p. 127. 



4 White, Ent., 1889, xxn. p. 51. Compare the fact that in another species of 

 Catocala (C. fraxini), the Clifden Nonpareil, the hind wings are normally bluish. 



