436 ALPINE EUROPE 



and glaciers is the so-called glacier-flea (Desoria glacialis), a member of the 

 Thysanura. Thousands of these hairy insects may be taken below the peak of the 

 Fingenhorn. A harvest-spider (Phalangium glaciate), found at a height of 11,500 

 feet, is bluish white in colour with cloudy grey marks, black angular spots on 

 the abdomen, and white circles round the legs ; its length being about a quarter 

 of an inch. 



snails A few of the snails of the lowlands are represented by allied 



and worms, species or races in the Alps. The Roman snail (Helix pomatia) 

 occurs, for instance, in a local form up to 6000 feet above the sea, while one of the 

 garden-snails (H. arbustorum) is represented by a small variety at a height of 

 7000 feet, where the glass-snail (Vitrina diaphana) is replaced by the ice-snail 

 (V. glacialis). Of the worms it must suffice to say that the Alpine flat-worm 

 (Planaria alpina) is remarkable on account of being blind when dwelling in dark 

 caves or in deep water, although it can see in situations where vision is of use. 



