Response of bumblebees to uni- and multi-directionally signalling flowers (Hymenoptera : Apidae : Bombus terrestris)

摘要

The size and orientation of the visual signalling display of flowers are key factors for the attraction of flower visitors. In the present study the consequences of a strategy by which flowers display signals in multiple directions were compared with a strategy by which flowers display signals in one direction for the attraction of bumblebees. When dummy flowers were placed 10 cm apart, bumblebees preferred the dummies with a three-directional over those with a uni-directional signalling area of equal size. If the inter-dummy distance was extended to 40 cm, they exhibited no preference for either type of dummy flower. However, when the signalling-area size of the dummies with three-directional signalling area was tripled, the bumblebees' preference for dummies with a three-directional signalling area was re-established, even with an inter-dummy distance of 40 cm. The results are discussed with respect to floral visual signalling strategies in dependence on floral density and the visual flower detection strategies of bumblebees.