Electro-reception in bumblebees

• Main Author: Clarke, Dominic
• Published: University of Bristol 2015
• Subjects: 595.79
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.701814

Bees use a wide range of senses to find flowers, detecting floral cues such as colour, shape, texture and fragrance. These floral cues allow bees to remember flowers that have been rewarding in the past and recall this information to identify con-specific flowers in the future. In this study, a previously unappreciated sensory modality in bumblebees (Bombus terrestris) is described: The detection of floral electric fields. These fields act as floral cues and can be used by bees to identify rewarding flowers while foraging. Like visual cues, floral electric fields exhibit variations in pattern and structure which can be discriminated by bees. Information from floral electric fields is shown to contribute to the complex array of floral stimuli that together facilitate learning and memory of floral rewards. A novel device for measuring the foraging activity of bees is described, and data generated by the device is used to determine under which atmospheric, meteorological and electrical conditions bees forage. The associated floral electric field strength under these conditions is calculated using a combination of atmospheric electric field data and finite element modelling techniques. Finite element models are used to design and validate experimental proxies for floral electric fields that are used to provide ecologically relevant electric field stimuli for behavioural and mechanical studies in the laboratory. Two putative electric field sensors, antennae and sensory hairs, are examined using laser Doppler vibrometry. Their mechanical sensitivity to a wide range of applied electric fields is measured. Both hairs and antennae show a mechanical response to floral-strength electric fields, though this response is between 2 and 11 times greater in magnitude than that of the antennae under identical stimulation. Hairs require a minimum stimulus voltage 5 times smaller than antennae. They show a mechanical response at roughly 2.5 times the distance from a given stimulus source when compared with antennae. This evidence combined with electrophysiological data from other authors strongly supports the hypothesis that bumblebees detect electric fields with mechanosensory body hairs.