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Predation on the Soil-Dwelling Stages of the Winter Moth at Wytham Woods, Berkshire

R. East
Journal of Animal Ecology
Vol. 43, No. 3 (Oct., 1974), pp. 611-626
DOI: 10.2307/3526
Stable URL: http://www.jstor.org/stable/3526
Page Count: 16
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Predation on the Soil-Dwelling Stages of the Winter Moth at Wytham Woods, Berkshire
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Abstract

(1) The components of the mortality of the soil-dwelling stages of the winter moth were studied beneath twelve oak trees in Wytham Woods, Berkshire, during one winter moth generation. (2) The total mortality inflicted by soil-dwelling predators (k5) was divided into three consecutive mortalities: [Note: equation omitted. See the image of page 624 for this equation.] where kL is the mortality of larvae between dropping from the canopy and pupating in the soil, which was measured as the difference between the logarithms of the density of falling larvae trapped in metal trays and the initial density of pupae determined by soil sampling, kP is the mortality of pupae, which was estimated by planting winter moth cocoons, some within areas where predators were excluded, and kA is the mortality of the flightless adult females between emergence and climbing the tree trunks, which was estimated by capture-mark-release-recapture of females. (3) Average estimates of the mortalities, expressed as percentages of the population of healthy larvae which dropped from the canopy, were 14% for larval mortality (kL = 0.06), 62% for pupal mortality (kP = 0.55), 5% for adult mortality (kA = 0.11), and 81% for total predation in the soil (k5 = 0.72). (4) Pupal predation appeared to be mainly due to carabids and staphylinids. Carabids were estimated to have destroyed 38% (23% attributed to Abax parallelopipedus and 15% to Feronia spp.), Philonthus decorus and perhaps other staphylinids 30%, and small mammals 4% of the initial population of pupae. (5) Larval and adult mortalities were not detectably density-dependent, but pupal mortality was density-dependent between trees with different winter moth densities. The results of cocoon planting and pitfall trapping of predators suggested that this density-dependence may have been due to the behavioural responses of Philonthus and Feronia to winter moth density.

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