INTRODUCTION. XUl 



the pigmental red and brown to its highest development black. 

 That the black in many species is readily deducible from red or brown, 

 may be seen in such species as Pararge cegeria, Epinephele hyperanthus, 

 Satyrus semele and Lyccena artaxerxes among the Diurni, in the black 

 varieties of Xylophasia polyodon vars. infuscata and cethiops, in Bisulcia 

 ligustri var. nigra, Xylophasia rurea var. nigrombida, Apamea didyma 

 vars. lugens, nigra, albistigma and leucostigma, Helotropha leucostigma and 

 its var. albipuncta, TripTicena orbona var. nigrescens, Orrhodia ligula and 

 endless other NOCTTLS:, in all of which the transition is most marked. 

 Probably no species shows the same perfect range of colour as do Xylo- 

 pliasid rurea and Agrotis tritici. In both species, the range extends from 

 almost pure white to black with intermediate yellow, ochreous, red 

 and brown forms. Now all these examples of black species are 

 probably pigment blacks, i.e., positive developments of pigmented scales 

 which remain pigmented. 



Very different are the cases in which non-pigmental black scales 

 supersede and replace pigment scales. I have a specimen of Vanessa 

 urticce with the hind wings purely black, the red pigmented scales 

 being undeveloped, which is probably a case of this kind. We get 

 another change in which a probably unpigmented scale replaces another 

 unpigmented, as in Amphidasys betularia var. doubledayaria, Tephrosia 

 biundularia var. delamerensis, Melanthia rubiginata var. plumbata, M. 

 albicillata var. sn/usa &c., in all these instances black replacing white. 



But blacks are very deceptive even in the most closely allied 

 species. Thus the black spots in the hind wings of Arctia villica, 

 CallimorpJia hera &c., are readily changed to brown, the black of C. 

 dominula slightly so, whilst that of A. caia is most absolutely immovable. 

 But probably the most deceptive black of which I know, is that in the 

 velvety fore wings of Arctia villica. This intense colour is only a 

 slight modification of the brown in its ally A. caia, and is readily 

 changed into a brown identical with that in the latter species. In the 

 same way, the intense black of Mamestra persicarim is only an extreme 

 development of brown, and shows its pigmentary character at once on 

 exposure. Another interesting peculiarity in the development of black 

 came under my notice. As is probably well-known, the black band 

 on the hind wings of Catocala is very immovable. In all our species 

 of this genus, it is almost impossible to modify it to any appreciable 

 extent. Catocala fraxini appears to offer a peculiarity in the genus in 

 having no coloured base to the hind wings (within the black transverse 

 band), but to be uniformly black to the base of the wing. But if the 

 species be held up before a strong light, and the wings looked through, 

 this black area is distinctly divisible into two as in the remaining 

 species of the genus. The first is a black band, identical with the 

 transverse band, which is normal in the genus, the other comprises 

 the normally coloured basal area. But, although these areas look 

 identical and are practically indistinguishable when looked at from 

 above, yet, holding a specimen to the light shows that the transverse band 

 is opaque, absorbing all the light that falls on it, whilst the basal area 

 is only superficially black, transmitting a great proportion of the light 

 that falls on it and therefore readily capable, we may assume, of 

 becoming pigmented. 



Having now run through the first series with regard to genetic 

 development, we have now to deal with the second series. This, as I 



