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Spatial distribution of larvae of the mosquito Culex tritaeniorhynchus summorosus in a rice field area

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Title: Spatial distribution of larvae of the mosquito Culex tritaeniorhynchus summorosus in a rice field area
Other Titles: 水田地帯におけるコガタアカイエカ幼虫の空間分布
Authors: Mogi, Motoyoshi / Wada, Yoshito
Authors (alternative): 茂木, 幹義 / 和田, 義人
Issue Date: 30-Jun-1973
Publisher: 長崎大学熱帯医学研究所 / Institute of Tropical Medicine, Nagasaki University
Citation: 熱帯医学 Tropical medicine 15(2). p69-83, 1973
Abstract: Spatial distribution of Culex tritaeniorhynchus summorosus larvae was studied in a rice field area surrounded by low hills, common in Nagasaki Prefecture. Rice fields in the area were about 15 hectares (roughly 500 rice fields), and among them 100 rice fields made of 11 groups were selected as study plots from various parts of the area. The study was done from May to October and the results were as follows. Larvae of Culex tritaeniorhynchus summorosus tended to concentrate in rice fields situated in some part of the whole area at a certain time and the position of such part changed during the period of mosquito occurence. Moreover the density level differed, sometimes markedly, among rice fields situated closely in a same group. These results are interesting in relation to the population study of this mosquito. Firstly, they ascertain our previous report that the number of rice fields examined should be increased, even though the number of dips taken from a rice field is decrease to only one, for estimating the relative density of the whole area in maximum efficiency. Secondly, they show that one rice field should be considered as one of natural unit for larval population in a rice field area. The latter seems to be very significant for understanding the processes of population fluctuation of this species, for density effects by overcrowding of larvae may act in some rice fields, while density in many other rice fields is remained low. / 長崎県に多い山間の水田地帯で,コガタアカイエカ幼虫の空間分布を調査した.調査地にある約15ヘクタール(およそ500枚)の水田のいろいろの部分から全部で100枚の水田を選び,5月から10月まで,原則として週に1回調査をした.その結果,コガタアカイエカ幼虫の密度の高い水田は,ある調査日には特定の場所に集中している傾向があること,その場所の位置は調査日ごとに変化していくこと,更に,隣合った水田で幼虫密度が著しくちがうことも珍しくないことが明らかになった.この結果は,広い地域のコガタアカイエカ幼虫の密度を知るためには,その地域内のいろいろの場所でなるべく多くの水田を調査しなければならないこと,及び,コガタアカイエカ幼虫個体群にとっては,個々の水田が1つの小単位となっていることを示している.後者は,コガタアカイエカの個体数変動の過程を解明していく上で極めて大切な観点であると思われる.何故ならば,大部分の水田の幼虫密度が低い時でも,一部の水田では過密による密度効果が働く可能性があるからである.
URI: http://hdl.handle.net/10069/4135
ISSN: 03855643
Type: Departmental Bulletin Paper
Appears in Collections:Volume 15, No. 2

Citable URI : http://hdl.handle.net/10069/4135

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