SEASONAL POLYMORPHISM. 137 



reaching its gigantic size. I should call bryonides those races of 

 bn/oniae which produce this third generation ; it remains to be seen, 

 whether the features described by me are peculiar to the Western Alps, 

 or are distributed more broadly. Strangely enough the variations of 

 vapi in these mountains, so well known to entomologists, remain to be 

 discovered. Stauder, I.e., p. 142, says that Sheljnzbko, in the Iris for 

 1913. p. 20, has re-named my bri/oniiles neobn/oniac, because he had 

 already used the former name in the Rev. Riisse d' Kiitoni., ix., p. 384 

 (March, 1910), for some other form. 



Grade II. may be described on broad lines as still having, like 

 grade I., the underside similar to that of first brood, but exhil)iting on 

 upperside characters distinctly showing it belongs to a summer one. 

 The underside differs very little from that of a southern spring genera- 

 tion, such as vidnarix, Vrty., except that the ground-colour is usually 

 of a bright canary yellow ; from its own first brood septentrionalb it 

 differs in that the streaks are thinner and bright green or greyish green, 

 instead of dark olive green ; they are, notwithstanding, always bold and 

 sharp in outline and reach the outer margin on all the nervures. On. 

 upperside the apical crescent of the male and its discal spot are quite 

 summer-like in tone of colour and shape; in the female the crescent is 

 not so broad and continuous as in the following grades and the 

 neuration is always thinly dusted with grey on all its extent and bears- 

 sharp black streaks at the terminal end of all the nervures of forewing; 

 m some individuals all these streaks may be quite pronounced and this,. 

 of course, is more frequent in localities where the race approaches 

 grade I. I take as my " typical" series the one I have received from 

 L. Dupont, collected at the Pont-de-l'Arche (Eure) in Northern France, 

 during the whole of July. My specimens from the south of England 

 correspond to them perfectly, just as the English first generation 

 septeutrionalis extends to the Eure. I propose for this second generation 

 of race septentricmolis, Vrty., the name of praenapaeae to recall the 

 name which is usually used for it, but indicate that it does not 

 exhibit to their full extent the features of Esper's true nupacae. 



Grade III. is the first which stands clear of all the features of the 

 first generation: on underside the nervural streaks of hindwing 

 l)ecome pale, shaded in outline and fadeaway towards the outermargin ; 

 in the females their extremities are in fact often quite obliterated ; 

 the ground colour of these wings is never bright canary yellow, but 

 very pale yellow, or ochreous, or white. On upperside of male the 

 true pattern is a little more extensive and sharper, that of the female 

 exhibits a more compact and extensive triangle at apex ; in this sex 

 the nervural pattern is usually quite obliterated on the basal half of 

 the wings and also as far as the margin on the second cubital and on 

 the anal nervures, only thin streaks remaining at the end of the other 

 nervures ; of course, there are exceptions, more or less frequent, 

 according to localities. This race seems to have a vast distribution 

 from Central France eastwards; it probably is the commonest in 

 Central Europe generally. It extends as far north as the Oise and the 

 series I select as " typical " was collected by D. Lucas at Compiegne, 

 in that Department, during the end of June and in July, evidently in a 

 locality drier and warmer than the Pont-de-l'Arche, although it is 

 slightly further north. I name it subnapaeae, mihi. 



