CLIMATAL CONDITIONS WITH KEFERENdE TO RHOPALOCERA. 101 



var. elens, Ccenonympha immphiliis var. lylliis, Melitcea didijma 

 var. alpina, some of them being exclusively found at the lower 

 elevations. 



Now respecting ocellation. Dr. A. K. Wallace's theory to 

 account for the predominant character which manifests itself in 

 the Satyridae, as well as in other groups of butterflies, namely, 

 in the submarginal ocellation of both the upper and the under 

 sides of the wings, is that the eye-like spots are useful for pro- 

 tective purposes. Being situated at a distance from the most 

 vital parts of the insects, he considers that they are the results 

 of natural selection pure and simple. The enemies of the 

 butterflies, principally birds, he presumes, would most likely 

 make for the most conspicuous part of the insect, both when at 

 rest and when flying, and these would in most cases be the 

 ocelli. This being so, it would afford the possessor a chance of 

 escape. In this connection I may here remark that I once 

 captured a specimen of Colias ediisa which showed unmistakable 

 signs of having been so attacked, and of its consequent escape. 

 Some small bird had probably bitten at the eye-like spot upon 

 the under side of one of the posterior wings while the butterfly 

 Avas in repose, as a piece had been bitten clean out of both sides 

 from thence to the hind margin. I have frequently seen speci- 

 mens of the Satyridse served in a similar manner. 



Presuming that Dr. Wallace is correct in his hypothesis, I 

 have endeavoured to prove it by investigating the conditions 

 under which ocellation exists in the Alps and the Pyrenees, 

 where there is plenty of scope for an enquiry of the kind, but 

 the data and material at present collected are inadequate to 

 enable me to make any definite pronouncement either in favour 

 or against his hypothesis. I first of all started with the 

 assumption that ocellation would appear more highly developed 

 upon the wings of those specimens occurring at the lower levels 

 and at the lower latitudes. But in this respect I have at present 

 found the evidence largely of a negative character, which is, 

 however, equally discomforting to those who consider that the 

 abundance of sunshine is the direct cause of the increased 

 ocellation. Thus, while there are some species, such as Erebia 

 ligea and Ccenonympha arcania—ii we consider the fornis euryale 

 and satyrion respectively only alpine varieties — exhibit increased 

 ocellation at the lower altitudes, others, such as Pararge mceni, 

 Erebia stygne, and Ccenonympha pamphiius, do not appear to be 

 similarly affected. 



These facts, taken in conjunction with those almost equally 

 as negative respecting the melanistic tendencies of butterflies 

 at high altitudes, evidently belong to the same category of 

 phenomena. The only solution out of the difficulty I can see is 

 that both melanism and ocellation were originally developed at 

 the lower levels for protective purposes, where the organic 



