Studies in Population Physiology: The Relation of Numbers to Initial Population Growth in the Flour Beetle Tribolium Confusum Duval

Chapman ('28), working with the confused flour beetle Tribolizirn confiusumn Duval, presented evidence demonstrating that a condition of equilibrium, measured in terms of number of individuals per gram of flour, is eventually reached within each population which is approximately uniform irrespective of the environmental size or the initial population density. In table III of his paper, reproduced herewith, he has recorded data, which in addition to supporting his own conclusions, open to experimentation another phase of the problem. Allee ('3I), interested in reviewing the effects of crowding on organisms, has analyzed this data. He shows that for the first periods in the development of the beetle population, namely eleven and twenty-five days, the greatest increase in numbers, in terms of eggs and early instar larvae per female day, comes at the initial population of four, while initial populations of eight or sixteen show a more rapid increase at eleven (lays than that given when only one pair was present. About this phenomenon, Allee remarks ('3I, P. I8o), " This indicates that there is an optimum initial population-medium relationship, which, for certain volumes of medium, is different from that given by the smallest population present." Chapman's original data are presented in table I together with a recalculation to show the rate of increase per female day at all population densities tried. The work to be reported in this paper has been directed towards finding by more extensive experiments whether the initial rate of population growth is usually greater in these beetle populations when more than one pair of beetles is present. CONDITIONS OF EXPERIMENT