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

J. Davidson and H. G. Andrewartha
Journal of Animal Ecology
Vol. 17, No. 2 (Nov., 1948), pp. 193-199
DOI: 10.2307/1484
Stable URL: http://www.jstor.org/stable/1484
Page Count: 7
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Annual Trends in a Natural Population of Thrips imaginis (Thysanoptera)
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Abstract

During 1932-8 the numbers of adult Thrips 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 three components due respectively to (a) the natural growth of the population; (b) the influence of weather, about the time the sample was taken, on the activity of the thrips in seeking out flowers; (c) the influence of the weather throughout the year on the rate of multiplication of the insects. The same trend of population tends to be repeated each year, and it is possible to represent the average trend for 7 years by a smooth curve. The average trend during the period 1 September to 30 November (when the population is increasing rapidly) may be represented by part of a curve fitted to the logistic formula [Note: equation omitted. See the image of page 199 for this equation]. The sources of variability referred to (b) and (c) above have been discussed in general terms in this paper, and it is hoped to deal with them more particularly in a later paper.

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