The Non-Use of Sleeping Substrate by the Sympatric BeesAmegilla florea urensandA. senahai senahai(Hymenoptera: Apoidea)

Abstract

Few studies have addressed the use of overnight substrate by congeneric bee species, although sleeping bees with other insect taxa or other bee families have been found to share the same substrates. We observed the sleeping aggregations of two sympatric bees, Amegilla florea urens and A. senahai senahai, to determine whether they shared the same substrates for sleeping on Ishigaki Island, Okinawa Prefecture, Japan. Many sleeping aggregations were found in broad-leaved deciduous forests and were patchily distributed along a pathway in broad-leaved evergreen forests in June for 2 years. Overnight aggregations formed on the leaves of monocotyledons or the fine roots of trees exposed on the slope of a bare cliff along the edge of the pathway. Neither species showed preference for any particular substrates. Over 2 years, we found 1 A. f. urens male aggregation, 6 A. s. senahai male aggregations, and 88 A. f. urens female aggregations. A sleeping site with aggregations of both Amegilla bee species was observed only once. Although no physical contact or mating approach es among sleeping individuals in each species were observed during the night, conspecific individuals slept close to other individuals in the aggregation. We suggest that single species aggregation would have an advantage for conspecifics to increase the night survival rate by sharing information such as predator attack.