Timing of male territorial flight and foraging of the large carpenter bee Xylocopa appendiculata related to serotonin in the brain.

Abstract

To determine how males of the large carpenter bee, Xylocopa appendiculata, maximize access to females while minimizing energy cost and acquiring energy for territorial flights, we investigated the times of territorial flights by males and foraging by males and females. Males were present continuously in territories from 8:00 to 12:00. They approached, chased, and excluded conspecific males from their territories. In the laboratory, males showed higher locomotor and flight activities in the morning and lower activities in the afternoon. Both males and females visited flowers from 8:00 to 16:00, but the most frequent visits were earlier in females (10:00-12:00) than in males (12:00-13:00). Relative body weights in territorial males often increased. These results indicate that the males time their territorial flights to maximize contact with females and obtain nectar as fuel between and after the territorial flights. The time-related territorial flight in males might be based on a time-keeping system in the brain. Brain levels of serotonin and its precursor tryptophan were significantly higher in males collected at 16:00 than at 11:00, suggesting a relation between time-related territorial flight and serotonin synthesis in the brain.