88 The Field Naturalist's Quarterly May 



cows, who, working downward from the highest pastures 

 as the summer draws on, will eventually graze the whole 

 mountain-side, with disastrous results to food - plants and 

 the larvae upon them. 



As a good example of the devastation a herd may 

 work, 1 recall a mountain spur above Zinal which rejoices 

 in the significant title of the Roc des Vaches. The side 

 exposed to the sun, where the pasture was fattest, pro- 

 duced practically nothing ; but once over the top and 

 down to the rougher slopes away north, all sorts of in- 

 teresting butterflies put in an appearance. It was here 

 that I made my first acquaintance with the peculiarly 

 Alpine species Oeneis aello, which remotely resembles the 

 familiar Grayling {Satyrus semele) of our British chalk 

 downs. So far as Switzerland goes, in one year it is 

 only to be taken on the western side ; in the next it is 

 confined to the eastern portion. It clearly takes, there- 

 fore, two years to pass through its several stages ; but 

 what circumstances have caused this eccentricity of ap- 

 pearance can only be guessed at. Possibly it is the 

 result of an exceptionally severe or an exceptionally mild 

 season retarding or developing quickly the ova or larvae 

 in one region, while the other has remained normal. For 

 I do not find that elsewhere than in the Alps aello indulges 

 in this strange partiality. But in any case the division is 

 of old standing, as it is noticed by the earliest observers 

 of the species. The name Chionobas, the "winter flier," 

 originally given to the family, conveys a fair idea of the 

 arctic localities it affects ; for, though aello is the sole mid- 

 European representative, it has several cousins in Norway, 

 Lapland, and Siberia. As a sporting insect — that is to 

 say, an insect which insures a good run over a difficult 

 country — it is without a rival. Inconspicuous in colour- 

 ing, it is up and away from the rocks on which it sits 

 before the eye can fix its identity ; and the high wind as 

 often as not prevailing lends it additional speed, as well 

 as very quickly reducing the wings to shreds. I have 

 never discovered it in any quantity. Single specimens, 

 the worse for wear, run down in the open after a stiff 

 climb, or secured by a chance twist of the net as they 

 whirled down wind and past me, make up the few that 



