THE TUNDRA AND ITS FAUNA 29 



lay their eggs in the autumn (except in the case where 

 there are two annual broods), and these eggs pass the 

 winter as eggs, or, if the larvae hatch, they winter in 

 a very undeveloped state. In the spring, activity is 

 early resumed, and the life-history is rapidly passed 

 through, so that the butterflies appear in summer. In 

 Greenland, butterflies do not appear till the middle of 

 July. If they lay their eggs, and these hatch at once, 

 the resulting larvae have, in the colder parts, only some 

 flve weeks before winter sets in. Activity does not 

 recommence till at earliest the first week of the follow- 

 ing June, and as it cannot be supposed that the animals 

 can pass through larval and pupal life before the onset 

 of cold, they must pass a second winter in the larval 

 state, the butterfly emerging in the following July to 

 lay its eggs and die. This great lengthening of the life- 

 history cannot be ascribed wholly to the cold ; we must 

 suppose that it is also due to the fact that caterpillars 

 must necessarily wait in spring until their food plants 

 have made some new growth. This life-history, there- 

 fore, again emphasizes the baneful effect on animal life 

 of the scanty development and slow growth in spring of 

 the plants of the tundra. 



In addition to insects, a few earthworms occur in the 

 warmer parts, and there are a few land and fresh-water 

 shell-fish and some spiders and mites. In general, how- 

 ever, it may be said that among the invertebrates the 

 insects are the most conspicuous and numerous forms. 



As a pendant to this picture of life on the tundra 

 we may add a brief consideration of the animals of the 

 shore, which, as we have noticed, have considerable 

 direct and indirect importance for the land animajls. 

 Man in these regions is practically dependent upon the 

 sea for food, for fuel, and for clothing, for the land 



