樹上性小型哺乳類調査の巣箱で確認されたミカドオオアリ： 営巣場所選好性とコロニー組成の季節推移

抄録

Ants play an important role in forest ecosystems in terms of biomass and various biological interactions, but non-destructive continuous observation of colonies is difficult for species nesting in trees. During the investigations of forest arboreal small mammals using wood nest boxes between January and December 2021, nestings of Camponotus kiusiuensis Santschi were observed at high frequencies in a census site on Mount Kyougatake, Saga Prefecture, Kyushu, Japan. We surveyed the nesting site preference of C. kiusiuensis and conducted monthly observations of colony compositions from spring to winter. Among three types of nest boxes, small (500 cm³), medium (1,000 cm³), and large (2,000 cm³), C. kiusiuensis nested in the large nest boxes at significantly higher frequencies. Although the nest boxes were either set at low (1.5–2.0 m high) or high (3.5–4.0 m high) positions of trees, no significant differences were detected in the nesting sites between them. The number of colonies was the highest in April and it gradually decreased from spring to autumn. In the nest boxes in which colonies of C. kiusiuensis were continuously observed until autumn, the developmental stages of immature individuals inside were almost uniform: larvae were observed from April to June, pupae in July, and many adults including males and new alate queens were found in August and September. No or very few ant individuals were observed in October and November, suggesting that workers moved the larvae to other places in late autumn. Based on our observations, the arboreal nest boxes seem not to be suitable sites for overwintering.