life's borderlands 245 



in the deep waters of the Norwegian Sea, and in all these 

 places with temperatures between 28.4° and 32° animals are 

 especially abundant. 



Almost everywhere on land for at least part of the year the 

 temperature rises above the freezing point. Even if the ground 

 be perpetually covered with snow or ice there will be little 

 warm islands consisting of the dark patches of dirt lying on 

 the snow which will support a number of different plants and 

 various insects. Such isolated verdant spots are often an in- 

 teresting and conspicuous feature of glaciers. 



A few warm days in winter incite to activity numerous kinds 

 of flies, moths, wasps and other insects which fly or crawl 

 about and then, when the sun gets low or when the cold re- 

 turns, become again inactive, falling apparently lifeless on the 

 snow. One of the commonest, most conspicuous and most 

 active of these types is the little snow flea. 



In the colder parts of the northern hemisphere there is a 

 strange insect, a wingless tipulid — ■ crane-fly or daddy-longlegs 

 — which reverses the usual habit of insects in living in summer 

 as a grub or larva under decaying leaves and becoming an 

 active adult in the coldest months of the year. These insects 

 are most active in cold snowy weather from January to April, 

 even when the temperature is below zero, walking rapidly across 

 the surface of the snow in perfectly straight lines. It has been 

 noticed in April that if in the morning the sun shone brightly 

 causing a slight thaw a few would be visible; but if the 

 weather changed in the afternoon and became colder with a 

 flurry of snow large numbers would come hurrying from all 

 directions. They are very sensitive to warmth and will die in 

 a few minutes if carried in a warm hand. 



There is another insect belonging to an entirely different 

 group, a wingless panorpid or scorpion-fly, looking somewhat 

 like a young grasshopper, which has similar habits. 



If animals thrive in very cold water, do they thrive equally 

 well in high temperature? They do not, for a number of differ- 

 ent reasons. On visiting a museum or reading a book on zq- 



