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Temporal and Spatial Distribution, Growth and Predatory Behaviour of Toxorhynchites brevipalpis (Diptera: Culicidae) on the Kenya Coast

L. P. Lounibos
Journal of Animal Ecology
Vol. 48, No. 1 (Feb., 1979), pp. 213-236
DOI: 10.2307/4110
Stable URL: http://www.jstor.org/stable/4110
Page Count: 24
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Temporal and Spatial Distribution, Growth and Predatory Behaviour of Toxorhynchites brevipalpis (Diptera: Culicidae) on the Kenya Coast
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Abstract

(1) The prevalence of the predatory treehole mosquito Toxorhynchites brevipalpis is seasonal on the Kenya coast. Dry season conditions enforce severe population reductions which in turn increase the time lag between peaks in predator and prey abundance after the onset of rains. (2) The predator occurred in bamboo traps set in or near a forest in preference to peridomestic or cultivated zones and showed no height preference between 1 and 10 m. Predator larval distribution was clumped, and the number of predators per trap fitted a negative binominal. (3) Prey density in selected bamboo traps was reduced more than two- to threefold by the presence of predator larvae during periods of peak abundance. Decreases in median number of prey were associated with increases in the average instar class (age) of the predator and mean number of predators per trap. (4) Predators selected prey of their approximate instar class, and fourth instar predators preferred pupae to fourth instar prey in bamboo traps and/or laboratory simulations. (5) Aedes and Eretmapodites prey were consumed in preference to Culex in simple laboratory environments, but predator diet in nature is largely determined by the frequency of concurrence with different prey species. (6) Within a certain tested range both maximal prey consumption by fourth instars and killing by prepupae were linearly correlated with prey density, but prey densities associated with the predator in nature were, on the average, less than the range tested in the laboratory. (7) Fourth instar larvae weighed daily accurately described growth in the laboratory and predicted killing behaviour and the competency to pupate. The frequency of prepupal killing increased from near zero to over 80% between 30 and 40 mg, and 26 mg was the approximate weight threshold needed for pupation. (8) Most field-collected fourth instar larvae had not achieved a weight of 26 mg by the time of collection, suggesting that too few prey may limit growth of the predator under natural conditions.

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