VARIATION IN VANESSA URTIC^. 57 



compared with that in A. levana — prorsa, but when the behaviour 

 of these latter extreme forms is similarly tested they prove them- 

 selves to be just as susceptible to the effects of light and tem- 

 perature as V. urtica. When July and August belie their repu- 

 tation for warmth and sunlight, then the summer form var. 

 prorsa tends to drop out entirely ; the pupte, instead of emerging 

 in August, hybernate and come out in the next spring as typical 

 levana ;* but in the summer following, if the season is favourable 

 (normal), these will produce var. prorsa as usual, though it is 

 not unlikely that (the tendency being at once atavic and pro- 

 tective) a small percentage of the pupae hybernate even under 

 normal conditions. On the other hand, if the season is excep- 

 tionally hot, and also otherwise suitable to the insects, then var. 

 prorsa will generate twice, and thus tend to drop levana, though 

 this seems to happen rarely, because var. prorsa is the pro- 

 gressive form, and is therefore not supported in such a case by 

 hereditary tendencies. If two (perhaps never full) successive 

 broods of prorsa are to emerge, then already the first brood must, 

 in perhaps all its stages, have been influenced by abnormally 

 stimulating conditions. 



The inferences are obvious : — 1 (a) Facial variation is mostly 

 bound up with the conditions of light and temperature ; (b) 

 changes in facies, even of the most extreme kind, need not 

 disturb specifical identity. 



2. On the other hand, specifical divergence appears to be de- 

 pendent on an effective isolation of any one group from the type. 

 The facies of the new species — which begins as a local variety 

 (c/. the evidence successfully adduced by Prof. Standfuss) — may 

 either remain almost typical, or may be an exaggeration of one 



■'- The following record by Mr. St. Quintin, F.E.S., in the Ent. Eec. pt. ii. 

 1909, p. 45, adduces excellent evidence of the effect of a cool English season 

 on a brood oi A. levana. Mr, Quintin writes: — "In July, 1907, I divided 

 with a friend the ova laid in a cage by a Swiss female A. levana. When we 

 returned to England my larvae were kept in an unheated greenhouse, and 

 pupated, duly emerging in the spring of last year as the form levana. My 

 friend kept his larvae in a warmer house than I did mine, and they pupated 

 quite a fortnight earlier, and all emerged in September as the form prorsa, 

 with the exception of one individual, which passed the winter in the chrysalis, 

 and emerged in the March following as typical levana.'" Indian butterflies 

 adduce conclusive proof that one species may be dimorph — in the extreme 

 sense — in one locality and monomorph in another, dropping one of its forms. 

 Thus, according to the communication of Dr. Seitz {cf. Ent. Zeitschr. 

 Stettin, 1893, pp. 290-307), there flies on the Indian mainland Junonia asterie 

 among the rich vegetation of the wet season ; asterie is marked with beauti- 

 ful " eyes," which are said to represent dewdrops. Later, when the dry 

 season of withered leaves and bare trees comes round, there flies Junonia 

 asterie again, but now the fly is dark-veined and without "eyes." It resem- 

 bles a dry leaf in adaptation to the seasonal conditions, and bears the name 

 almana. Off the Indian mainland, now, there lies the evergreen Isle of 

 Ceylon, and there Junonia asterie flourishes also, hut only as the dewdrop- 

 form. Again, in adaptation, it has dropped its " dry-leaf form" almana. 



