346 THE ENTOMOLOGIST. 



Mauy examples could be given in support of this contention. I 

 will confine myself to a few. 



Numerous species of alpine plants which only live at great 

 altitudes upon the mountains in their native habitat can be 

 made without any difficulty whatever to flourish in gardens even 

 down to the sea-level. Witness, for instance, the many kinds of 

 alpine saxifrages and gentians, &c., which are in cultivation. 

 The various species of pines and fir trees which constitute the 

 typical arboreal conditions of the sub-alpine zone in the moun- 

 tains, and of the sub-arctic region of the horizontal isotherms, 

 can in like manner be successfully grown in places where the 

 temperature is considerably higher. There is no reason there- 

 fore whatever to conclude that their distribution either vertically 

 or horizontally is directly due to the climatal conditions. 



The same thing precisely holds good with regard to the 

 Lepidoptera, which are subject to the same general laws as the 

 plants which provide their pabula. 



There are, on the other hand, some powerful reasons for 

 supposing that many of the species of plants and animals which 

 are now confined to high altitudes upon the mountains, or exist 

 only in the high latitudes of the north, owe their survival almost 

 exclusively to the direct influence of the organic environment. 

 The particular organic competition with which they would have 

 to contend at lower elevations may be entirely wanting at the 

 higher ones. In the case of insects, their natural enemies, 

 birds, bats, moles, shrews, lizards, and frogs, are usually very 

 scarce in all the higher zones. 



In many parts of the Alps, where the mountaineers have 

 ruthlessly destroyed many of the more extensive forests of de- 

 ciduous trees, the conifers have taken their place, in some 

 instances springing up spontaneously, and at present success- 

 fully maintaining their ground against the oaks and the beeches. 

 The inference to be drawn from this fact is that the conifers are 

 capable of flourishing at lower levels than they at present 

 occupy, quite as well as at the higher ones, provided they are 

 precluded the possibility of competition from the more vigorous 

 oaks and beeches of the lower elevations. Whether the pines 

 and the firs will successfully prevent the encroachment of the 

 latter in the spaces which have been cleared for them, for several 

 centuries to come, is, I should venture to say, extremely doubt- 

 ful. On the other hand, the conifers, with their needle-like 

 foliage presenting a minimum of surface to the frost, alone 

 survive at the higher altitudes where the deciduous trees would, 

 by reason of their larger leaves, soon perish. 



The direct influence of the climatal conditions seems to act 

 more powerfully in curtailing the upper rather than the lower 

 limits of species. Many species of butterflies and moths thus 

 seem very sensitive to cold, especially in the pupa-state, as is 



