First survey of ground-dwelling ants (Hymenoptera: Formicidae) on the uninhabited Gaja-jima Island, the Ryukyu archipelago, Japan

The ground-dwelling ant fauna on the uninhabited Gaja-jima Island, the Tokara Islands, the Ryukyu archipelago, Japan was investigated, which was the first survey on ants of the island. Twenty-three ant species were found during a visit of only eight hours in daytime. Four of them were new records to the Tokara Islands. Of the four new records, the southern limit of distributions was renewed for three species. Three exotic species, Pheidole fervens, Tetramorium bicarinatum, and Tapinoma melanocephalum were recognized, which seems relatively low given that ten exotic species have been altogether recorded from the Tokara Islands. The relationship between invasion by ants and the scale of human activity is discussed.