Possible foraging benefits of bimodal daily activity in Proxylocopa olivieri (Lepeletier) (Hymenoptera: Anthophoridae)

We followed the daily and seasonal foraging patterns of the solitary bee Proxylocopa olivieri during two springs and summers in Har Gilo, Israel. During the foraging season, the bees exhibited a clear bimodal daily activity pattern. They foraged mostly before sunrise and after sunset. We hypothesized that this activity schedule entails foraging benefits. We found that snapdragon (Antirrhinum majus L.) was a major source of nectar for P. olivieri. Nectar production rates in snapdragon were significantly higher during the morning activity period of P. olivieri than during mid-day. Bees of numerous other species foraged on snapdragon, but their activity periods hardly overlapped with P. olivieri. Foraging activity in P. olivieri was highest at a combination of high (25-35°C) temperatures and low (1-100 Lux) illumination levels. We suggest that P. olivieri benefits from foraging at dawn and dusk on snapdragon, and possibly additional food plants, because of exploitation of the large amounts of nectar produced. A nectar enrichment experiment revealed that P. olivieri does not cease foraging because of lack of available nectar. We suggest that the P. olivieri's ability to fly at low light levels enables it to dominate a unique foraging niche.