Comparison of the Predator Fauna among the Citrus Orchards of Japan

Abstract

The fauna of predaceous insects was studied at 37 citrus orchards in various parts of Japan including Amami-Oshima, Shimabara, Omura, Yamaguchi-Oshima, Ehime and Arita. Among 16 species of the predaceous insects, Cybocephalus gibbulus, Saula japonica, Pseudoscymnus hareja, Scymnus hilaris and Stethorus japonicus are important predators of citrus pests. C_λ-index (MORISHITA, 1959) indicated a complete dissimilarity of the fauna of predaceous insects between Amami-Oshima and other parts, and a tendency of the reduced similarity among various parts other than Amami-Oshima as the latitude differed. The predators' density had a tendency to rise with the increase of pests' density. The higher density of predators was revealed at the orchards where no pesticide had ever been applied than at those applied. Locality difference of the spider fauna could not be found clearly because of the shortage of collected material, nevertheless the result suggested some difference.