Arctic Insects and Their Environment

Abstract

AbstractThe first part of this paper discusses the characteristics of the arctic environment as it influences insect life. The most important features are the low temperature, the low annual heat budget, the severe and often variable weather and the continuous daylight of the growing season. A certain uniformity in aspect of the tundra environment is mentioned. Some microclimatic and regional differences are considered and a definition of thelow arcticlife zone is proposed.The make-up of the arctic fauna is considered in the second section. In the low arctic there may be up to 5% of the number of species found in a comparable temperate area, and in the Queen Elizabeth Islands about 1%; but the representation of the various groups of insects in the arctic varies greatly, the Diptera, and especially the Chironomidae, being by far the most numerous. The fauna is derived from that of the north temperate zones, by extensive reduction and by a limited development of endemic forms up to, but rarely beyond, the specific level. Many of the endemic forms seem to be adaptations to the special features of the environment, especially the low temperature and short season; while others appear to show a loss of specialized features, e.g. of colour or pattern, in relation to the small number of species in their environment and the consequent lower level of biotic interactions. The arctic Lepidoptera are frequently cited in these sections and a number of species are figured.The paper concludes with a discussion of the general reasons why so few species are found in the arctic. The arctic environment is not inherently simple and does not forbid a greater diversity, yet in fact very few species occur. It seems to lie beyond the range of physiological tolerance of all but a very few of the forms of temperate origin. But, given time, there is no apparent reason why a greater diversity should not develop, although the evolutionary process is probably slower in the arctic and is always liable to be set back by climatic disasters, from the last of which the fauna has only just begun to recover. It is suggested however that the arctic will always tend to lie towards the limit of the physiologically possible range because in fact the greatest continuity of evolutionary history has been in the tropics and most forms of life have thus been shaped in response to tropical conditions.