Another form in which I tried to investigate the same problem is _Coenonympha arcania_, which has one Alpine form known as _darwiniana_, and another, _satyrion_. In calling _satyrion_ a form of _arcania_ I follow Staudinger and other authorities, but I have never been quite satisfied that it should be so regarded. The differences between _arcania_ and _darwiniana_ are essentially differences of degree; _C. arcania_ occurs in places where there is cover, and reaches up the valleys usually as high as the mixed woods of deciduous trees, which is about 2,500 feet. The variety _darwiniana_, on the contrary, is an insect of treeless hillsides, and I regard it as a dwarf and possibly a stunted form. It would not greatly surprise me to find that with the application of good conditions _arcania_ could be raised from _darwiniana_ eggs, or that if _arcania_ larvae were starved they might give rise to _darwiniana_ butterflies. I have been unsuccessful in trying to rear the species, having lost the larvae by disease. Usually one does not catch _arcania_ and _darwiniana_ on the same ground, and as _Festuca ovina_--a typically hill-side grass--is a common food-plant of _darwiniana_ 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. Generally the sample from a given locality is fairly homogeneous.