The biology of insect populations

Abstract

Many features of the biology of insects are related to the fact that they occur not as isolated individuals, but as members of populations. These populations tend to occupy more or less restricted parts of larger habitats, they change in density from time to time and from one place to another, and they show varying degrees of spatial or reproductive isolation from other similar populations. They also interact with populations of other species (including other insects) and many such interacting populations may be integrated to form more or less well-defined communities. Populations are also subject to changes in genetic constitution and therefore evolve at various rates — mainly, it seems, under the influence of random genetic mutations and variously directed pressures of natural selection, though random processes of ‘genetic drift’ may also occur. Studies of the behaviour of insect populations and the environmental factors that influence them are not only of intrinsic ecological and evolutionary interest, but are also needed to understand and control those pest populations which are injurious to man, crops and domesticated animals.