Chap. VI] 



ANIMALS 



127 



The high regions of the Alps are indeed poorer in insects than the 

 surrounding lowlands ; yet, as Hermann Miiller has shown, flowers are 

 not less frequently visited by insects there than in the plains. More 

 important than the reduced total number of insects is the quite altered 

 numerical relation among the different groups. Thus, according to 

 Hermann Miiller, Apidae, except humble-bees, fall off rapidly in numbers 

 as the altitude increases. Lepidoptera, on the contrary, show a consider- 

 able increase. Accordingly bee-flowers decrease and lepidopteron-flowers 

 increase. The latter, according to Loew, number in the Alps 53 species, 

 but only 36 in the Westphalian lowlands. 



Many genera are represented in the plains by bee-flowers, in the Alps 

 by lepidopteron-flowers ; for example, Gentiana, Rhinanthus, Viola. One 

 and the same species may even 

 exhibit corresponding variations. The 

 flowers of Viola tricolor (Fig. 65, 2) 

 are short-spurred in the plains, corre- 

 sponding to the short proboscis of 

 the bees, their pollinators ; the variety 

 alpestris is long-spurred, corresponding 

 to the long proboscis of Lepidoptera. 

 The purely alpine Viola calcarata 

 has long-spurred lepidopteron-flowers 

 (Fig. 6,5, 1). Primula farinosa, accord- 

 ing to Hermann Miiller, has in the 

 plains, where its pollinators are bees, 

 a considerably wider entrance to its 

 flower than it has on alpine heights, 

 where it is practically visited by 

 Lepidoptera only. 



The Pyrenees are poorer in Lepi- 

 doptera than are the Alps, but on the other hand are richer in insects 

 that have not produced through natural selection definite forms of flowers ; 

 lepidopteron-flowers are accordingly feebly represented (MacLeod). 



The Norwegian plateau is poor in insects owing to the shortness and 

 wetness of the summer ; adaptations for cross-pollination have therefore 

 undergone a considerable reduction. 



Of the 76 alpine and arctic species of the Dovrefjeld, according to a compila- 

 tion by Loew, there are 2 anemophilous species (Oxyria digyna and Thalictrum 

 alpinum), whilst the 74 entomophilous species exhibit the following arrangements : 

 self-pollination is invariably or usually prevented in 12 species = 16-2 % ; self- 

 pollination as well as cross-pollination occurs in 40 species = 54 % ; self-pollination 

 is regular or easily accomplished in 22 species = 297 %. In comparison with the 

 Alps of Central Europe the alpine plants of Norway show a distinct falling off 



Fig. 65. 1. Viola calcarata. Lepidopteron- 

 flower ; long-spurred. 2. Viola tricolor. Bee- 

 flower ; short-spurred. Natural size. 



