The lunar periodicity of Sphecodogastra texana, a nocturnal bee (Hymenoptera: Halictidae)

Abstract

The behaviour of the nocturnal bee, Sphecodogastra texana (Cresson), was investigated during the summers of 1962, 1964, and 1965. Nests were dissected. Moreover, foraging activity was studied in detail, as the timing of the foraging period of the bee had been a subject of dispute in the past. It was found that the foraging of S. texana was based upon the lunar cycle and could be divided into two parts, the crepuscular period and the moonlight period. During the crepuscular period S. texana foraged only briefly between sunset and the end of twilight. When the moonlight period occurred, from the day after the new moon until about three days after the full moon, foraging continued as long as the moon was up. Lunar activity seemed to come as an extension of the twilight foraging as long as the moon was present before the bees plugged their nest entrances. Even when the moon was present during most of the night, if it rose after the nests had been plugged with sand by the bees at the end of twilight, no foragers could be found on Oenothera rhombipetala, the bees' pollen source. Further evidence of lunar periodicity was shown in a re-analysis of the daily fluctuations in numbers of S. texana caught in a light-trap by Chandler (1961), in brood cell contents as revealed by dissection of nests, and in the architecture of old nests excavated in August of 1964.