Spatial structure and dynamics of insect populations

Abstract

A strong tradition in insect population ecology has its roots in the early conceptual and theoretical analyses of population regulation (Nicholson, 1933, 1954; Nicholson and Bailey, 1935; Smith, 1935; Elton, 1949; Lack, 1954) and in the classical experiments of A. J. Nicholson on laboratory populations of blowflies (Nicholson, 1950, 1954, 1958). The key factor (Varley and Gradwell, 1960; Morris, 1963a) and life table analyses (Watt, 1961; Morris, 1963a) were developed for detailed studies of insect populations, to elucidate the forces that cause populations to oscillate and to unveil the identity and the strength of the density-dependent processes that would nonetheless ensure population regulation. Insect populations causing economic damage in forests (e.g. Diprion hercyniae, Neilson and Morris, 1964), cultivated fields (Brevicoryne brassicae, Hughes, 1963), and orchards (Cydia pomonella, Geier, 1964) were obvious (and well funded) targets for such studies (Clark et al., 1967). These studies were typically concerned with large populations, and the task was to describe, analyse and model the mechanisms that contribute to local population regulation. Many species are especially abundant only periodically, in which case the task is also to understand the processes that keep the density at a low level for long periods of time (Clark, 1964). A few populations are cyclic, and entomologists have asked which mechanisms might maintain the regular cyclic component in their oscillations (Baltensweiler, 1964).