THEOBALD, J C*; WARRANT, E J; Lund University; Lund University: Neural summation in night flying sweat bees

Megalopta are neotropical sweat bees that forage during only two time windows: after sunset and before sunrise. Thick forest canopies and the quick onset of darkness at tropical latitudes leave bees in profound darkness for these trips—20 times dimmer than starlight. Other insects that fly in this environment, such as moths, invariably possess superposition eyes, which increase light capture several hundred fold. All bees, however, have apposition eyes. Nonetheless, Megalopta survey the visual scene on exit, fly off to forage, and return to the entrance of a small stick hidden in a forest littered with similar sticks. The implication is that they perform difficult visual tasks despite the low signal to noise ratios produced by such darkness. With limited optical options, Megalopta may use neural mechanisms to improve signal to noise ratio. We investigated the theoretical effects of spatial and temporal pooling as they apply to bees in their natural habitat. Although sacrificing acuity, we found they could extend reliable vision to much lower light intensities. Further, the optimal summation was a close match to estimates derived from physiological, cellular, and behavioral data. We propose that neural mechanisms are critical to Megalopta‘s ability to forage in the dark, and allow them to exploit the night habitat, visually hidden from predators, and with reduced competition from other bees.