In this paper we analyse the measurements of population vital rates made byA. J. Nicholson (1957, Cold Spring Harbour Sympos. Quantitative Biol.22, 153–173) on laboratory cultures of the Australia sheep blowfly Lucilia cuprina (Wied.) and show that these measurements imply a progressive change in the demographic characteristics of the population during the course of the experiment. These changes, which are shown to be consistent with the changes which Nicholson observed in the stability of the population as a whole, imply evolution from instability to stability. We demonstrate that the observed changes in average population parameters are compatible with the operation of natural selection, a model of the competition between “wild-stock” and “post-experimental” type flies showing that under the conditions of the experiment a population initially containing only 1 % post-experimental type flies would change its composition to essentially 100% post-experimental type individuals over the 400- to 500-day time scale observed by Nicholson.
- population models
- insect population