180 PROBLEMS OF GENETICS 



winiana there can be little doubt that arcania feeds on some other 

 grass, probably woodland species. Colonies of arcania of varying 

 size and brightness are commonly found, and though a sample of 

 arcania, finely grown, from a warm Italian wood, presents a 

 striking contrast with darwiniana from an Alpine pasture, one 

 certainly may get samples which fill all the gradations. Gen- 

 erally the sample from a given locality is fairly homogeneous. 



Of satyrion I have little personal experience. I only twice 

 found it, namely at Zinal, and at Hallstatt in Austria, but it 

 occurs at Zermatt, Arolla, and in several Swiss localities above 

 5,000 feet, and I understand that it is the typical Alpine form in 

 the Engadine. With its darkened colour and reduced size it 

 might well be expected to be a still further stunted form of 

 darwiniana. Yet I have never found the one succeed to the 

 other at the higher levels. If darwiniana appears when Alpine 

 conditions are reached in a valley it will be met with up to the 

 highest level at which such butterflies live. Tutt was of opinion 

 that satyrion is a distinct species. 20 I once, at the top of the Vor- 

 derrheinthal caught a sample of darwiniana a few of which (males) 

 were so dark and had the eye spots so poorly developed that they 

 looked like transitions to satyrion. Otherwise I never found 

 any such transitional forms and they are certainly exceptional. 

 There is further a record 21 of satyrion having been taken flying 

 with arcania. This was near Susa, at about 2,000 feet I infer. 

 Mr. H. E. Page has similar specimens from Caud and from St. 

 Anton (Arlberg). The females, however, both of mine and of 

 Mr. Page's samples are a pale brown, quite unlike the females 

 both of arcania and of the dark Zinal satyrion. The difficulty 

 thus raised has not I think yet been considered by the authorities, 

 and it is possible that the Alpine forms of arcania are in reality 

 three, not two. 



The evidence taken together suggests, I think, that darwin- 

 iana is related to arcania much as so many of the Alpine varieties 



20 Tutt, J. W., Ent. Rec, XVIII, 1905, p. 5. In the same place he states that 

 on the Mendel Pass arcania "runs into" darwiniana and that in the Tyrolean 

 localities the transition is especially evident. Wheeler {ibid., XIII, 1901, p. 121) 

 expresses the contrary opinion, that satyrion does grade to arcania. 



21 H. Rowland-Brown, Ent. Rec, XI, 1899, p. 293. 



