INTRODUCTION. XV11 



Of the change of green to black we have an example in Eupithecla 

 rectangulata var. niyrosericeata. This variety is undoubtedly a direct 

 result of " natural selection," and the change is much more positive in 

 the males than in the females, the females becoming a darker and more 

 intense green, whilst the males become black. There is a distinct 

 banded form of Agriopis aprilina in which the central area becomes 

 entirely black, and the type of Moma orion has the black markings 

 duplicated. There are black forms a] so of Hypsipetes elutata and other 

 normally green species. 



As a pigmental colour, blue gives us but few examples, but its 

 unpigmented instances are very numerous. One of the best examples, 

 perhaps, of blue as a pigment colour, is that of Catocala fraxini. 

 This is identical in position with, and occupies the place of the normal 

 red and orange bands in the other species of the genus, and appears 

 identical in structure, bleaching somewhat readily like the reds. 

 The purple-tinged specimens of red species, such as Ellopia fasciaria 

 ab. manitiaria the bands of Epione cespertaria and E. apiciaria 

 are decidedly pigmental and developed through red, whilst that of 

 Selenia illustraria and that of Lasiocampa qmrcifolia, are clearly 

 traceable through the same colour. The blue spots in Vanessa io are 

 probably unpigmental and show an advanced development (probably 

 in a difference of scale structure) on the corresponding white spots in 

 V. urticce and V. atalanta. One of the most interesting blues we have 

 is that of Agrotis prcecox var. prceceps, and since the green of prcvcox is 

 highly pigmental it is probable that the blue of prceceps also is. It is 

 the only case 1 know among our British NOCTU^J, in which a green 

 pigment becomes changed to blue, although the change frequently 

 occurs quite naturally in the probably unpigmented green of Zygcena. 



I am rather inclined to think that the blue of Lyccena is largely 

 pigmental, and derived like their brown females through red or even 

 white. Certain it is, however, that blue and purple represent the 

 highest development of our pigmental colours. Among the species 

 in Lyccena corydon bleaches readily artificially, and the ordinary 

 male then looks identical with the natural white var. corydonius 

 found in Spain. A form of the male occurs at Dover with an ill- 

 developed row of spots (normal in the female) on the outer margins 

 of both fore and hind wings, and with a decided white band 

 edging it. Here the blue is distinctly traceable and changeable to 

 white. I have male L. icarus, similarly tending to form white (colour- 

 less) varieties. These were taken at Deal, in August 1887, which 

 will be remembered as a dry hot summer, in which the larvae probably 

 had to put up with a minimum of food, and hence there is some 

 suggestion of a connection between this want of food and the ill- 

 developed pigment. At the time I captured these pale males, I also 

 took a female with a white hind wing, and other strange forms. This 

 species bleaches artificially as also does L. tegon, and, arguing from 

 analogy, I should suppose most of the species are pigmental. It must 

 be remembered too, that the species of Polyommatus have excessively 

 soluble pigments, and the Polyommati and Lyccence are very closely 

 allied. Put into a damp box the " blues " rapidly change, the bright blue 

 of bellargus becomes green, as also do the blues of icarus, cegon, corydon 

 &c., in a less degree. But this is no proof of their pigmentary character, 

 any more than is the change of green to brown under similar con- 



