Abstract / Introduction / Summary:
A total of 21 ant species belonging to 11 genera in four subfamilies was collected from the Oki Islands. This corresponded to 23.9% of 88 species collected so far from Shimane Prefecture. The most species (19) were collected from Saigo Port. The average of the ant species collected at 6 ports was 13.7. The dominant ant species estimated by the ratio of occurrence to all of the honey baits (180) was Tetramorium tsushimae (0.45), followed by Formica sp. B (0.41), Temnothrax spinosior (0.14) and Camponotus japonicus (0.11). The similarity of species composition calculated by Nomura-Simpson’s Coefficient (NSC) was the largest (1.00) between Saigo Port and Beppu and Urago ports, and was the smallest (0.67) between Shibaura and Ni- furi ports. In this study, no alien ant species was col- lected from the Oki Islands. Monomorium chinense was collected for the first time in Shimane Prefecture. A difference of similarity in species composition among nine regions so far surveyed in southern Japan was found between the Northern and Middle Ryukyus.