MELIT^A PH(EBE VAR. OCCITANICA, STOJR. 169 



Melitsa phoebe var. occitanica, Stgr. 



By GEOEGE WHEELER, M.A., F.E.S. 

 I feel convinced that Mr. Tutt is mistaken in his notes on this 

 subject {antea, p. 105), not merely on the question of the occurrence of 

 the vars. occitanica and aetheria in Switzerland, which is a matter of 

 comparatively small moment, but in his main contention with regard 

 to local races. I am satisfied that it is only in a very limited sense 

 that such things can be said to exist at all. There can be no doubt 

 that the dominant forms of many butterflies are different in different 

 localities, and so far they may be called " local races," but it is most 

 unusual for these same forms not to occur as aberrations in localities 

 where some other form is dominant. In the majority of variable 

 species, i.e., those that vary widely and conspicuously, the directions 

 in which variation tends are well-marked and strictly limited, and it 

 often happens that those tendencies are in exactly opposite directions. 

 For instance, in the Erebiids there occur almost universally both the 

 tendency to lose and the tendency to accumulate eyed spots. 

 Numberless other instances will occur to the minds of those who have 

 made any study of variation, and those who have studied it in the 

 field will also be aware that, whilst it frequently happens that some 

 one form is dominant in any given locality, still, other forms proper to 

 widely different localities crop up from time to time as aberrations, 

 and that this is true even of the forms showing diametrically opposite 

 tendencies. For example, the type form of Erehia ijorije is the 

 dominant form on the western Swiss Alps, with a marked tendency 

 towards the nearlj- or quite spotless form eri/nnis, whilst the strongly 

 spotted form ^r/oy^^'.s is dominant on the eastern Alps of the Grisons, yet 

 the only example I succeeded in taking on a baddish day last year 

 above Pontresina was of the type form, already leaning towards 

 erytmis. Again, Anthocaris fii))rplrmia, with its dark green mottlings 

 on the underside hindwings, showdng but little white and less yellow, 

 is the usual form of the mountains, while the form of the Ehone 

 Valley is the var. liavidior with yellow nervures, lightish green 

 mottlings, and large patches of white ; yet the very lightest specimen 

 I have ever seen w^as taken at the far end of the Laquinthal amongst 

 a large number of the typical mountain form, and in the valley one 

 occasionally meets with specimens as dark as the average form of the 

 mountains. It would occupy too much space to work this out at 

 length in the present note, but it w^ould be well worth while to do so. 

 The outcome, however, of my observations and studies on the subject 

 is this: — -(1) Variation in certain directions, or more probably in one 

 particular direction is due to atavism. (2) Variation in the opposite 

 direction, and probably in various others, is due to an inherent 

 tendency in each species, and is the expression of the direction in 

 which new species will ultimately arise as modified descendants of 

 those at present existing, though, of course, great numbers of such 

 incipient species will never succeed in establishing themselves. 

 A further indication of this inherent tendency is to be found in the 

 fact, pointed out long ago by Darwin, that allied species tend to vary 

 in the same manner. This agam ought to be thoroughly worked out, 

 but it must suffice for the moment to point out, that, though this 

 similar variation in one direction is doubtless atavistic, variation in 



