Annual Trends in a Natural Population of Thrips imaginis (Thysanoptera)

Abstract

During 1932-8 in Australia the numbers of adult T. imaginis in roses were counted on 1773 days, giving a continuous record for the density of the population during 81 successive months. The total variability of the 1773 daily records may be considered to have 3 components: The natural growth of the population; the influence of weather, about the time the sample was taken, on the activity of the thrips in seeking out flowers; and the influence of the weather throughout the yr. on the rate of multiplication of the insects. The same trend of population tends to be repeated each yr., and it is possible to represent the avg. trend for 7 yrs. by a smooth curve. The avg. trend during the period Sept. 1 to Nov. 30 (when the population is increasing rapidly) may be represented by part of a curve fitted to the logistic formula: Y = d + [image].