176 BRITISH BUTTERFLIES. 



hindwingform, although he mentions the characteristic red lunules on 

 the upperside of the hindwing. There is considerable difference in 

 the development of the discoidal spots on the upperside of the $ s. 

 'Those with none might be termed ab. disco -ubsoleta, n. ab., 

 those with them only on the forewings disco-anteriora, n. ab., 

 with them only on the hindwings disco-posterior a, n. ab., on all 

 the wings disco-lunulata, n. ab. Although occurring almost every- 

 where aberrationally, there is no doubt that those from the plains of 

 Europe (including our chalkhill form) are usually without them, whilst 

 those of the mountains possess them, e.g., the specimens of the Geneva 

 ■district rarely have them, whilst the alpine^ s of Savoy and Switzerland 

 have them clearly marked; examples from Bourg d'Oisans are without 

 them, those from the Col du Lautaret, high up the same valley, 

 possess them strongly marked. They are strongly developed in 

 examples from Trafoi, Preth, etc., and occur in the Japanese form, 

 paeudaegon, etc. St. Petersburg examples, otherwise almost like our 

 British chalkhill form, have the lunules showing, which ours have not. 

 The variation in this direction is, however, easily traced. The race 

 with the most marked discoidal lunules of which we have knowledge, 

 is our Asiatic var. ongodai. The ground colour of the underside of the 

 J varies exceedingly, and has a distinct racial tendency. It exists 

 from almost pure white, through every tint of bluish-white, whitish- 

 grey, weak coffee- brown, and reddish-grey, but usually with distinctly 

 more variation than in the allied P. argyrognomon, which is generally 

 particularly uniform in the tint of its ground-colour. Usually the 

 white, bluish-white, and paler ground colours, are characteristic of 

 races inhabiting exposed open areas ; the greyer ground colours of less 

 exposed areas, or of high altitudes and latitudes, whilst the browner 

 are particularly characteristic of heathy localities on deep red sand or 

 dark gravel soils, the darkest coloured undersides that we know 

 •belonging to the specimens haunting the heaths of Fontainebleau 

 Forest, where also the ground colour of the underside of the allied /'. 

 •argyrognomon is even still more marked, and in the same direction 

 (especially in the second brood), indeed, the colour is darker than in 

 some $ s from other localities. This underside colour-variation, is 

 mentioned by Oberthvir, who, after noting the whiteness of that of 

 Jiypochiona, remarks (Etudes, xx., p. 28) that, in Brittany and in 

 England, the underside of the wings in the $ is no longer snow- white, 

 but bluish -grey. Blachier says that the $ specimens from Digue 

 (June), and certain examples from Vernet-les-iiains (July), are of a 

 very clear bluish-white colour beneath, sometimes almost as white as 

 the true hypochiona of Andalusia. The undersides of the J Bulgarian 

 specimens are whitish-grey, very like our chalkhill form in this 

 respect, ;is also are those from the St. Petersburg; the specimens from 

 Kreuznacb are, perhaps, a shade whiter, as also those from Bourg 

 d'Oisans, but those from the Col du Lautaret, a few miles further up the 

 Romanche valley, but 4000ft. higher, are distinctly darker grey, i.e., 

 of the mountain form. Of the Pvivnean examples in the I>rit. 

 Museum coll., those from Gavarnie and Vernet, have the underside 

 very bluish-white, but those from the Lac d'Oo are less bluish and 

 rather greyish-white in tint. We have dealt with the Gavarnie examples 

 (infra) as vars. pyrenaica and hypochionoides. Reverdin notes (in litt.) 

 that the underside of the posterior wings of a <£ from Divonne appears to 



