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 
five 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 animals. 
Man in these regions is practically dependent upon the 
sea for food, for fuel, and for clothing, for the land 
é 
