Abstract
The spontaneous occurrence of colour preferences without learning has been demonstrated in several insect species; however, the underlying mechanisms are still not understood. Here, we use a comparative approach to investigate spontaneous and learned colour preferences in foraging bees of two tropical and one temperate species. We hypothesised that tropical bees utilise different sets of plants and therefore might differ in their spontaneous colour preferences. We tested colour-naive bees and foragers from colonies that had been enclosed in large flight cages for a long time. Bees were shortly trained with triplets of neutral, UV-grey stimuli placed randomly at eight locations on a black training disk to induce foraging motivation. During unrewarded tests, the bees’ responses to eight colours were video-recorded. Bees explored all colours and displayed an overall preference for colours dominated by long or short wavelengths, rather than a single colour stimulus. Naive Apis cerana and Bombus terrestris showed similar choices. Both inspected long-wavelength stimuli more than short-wavelength stimuli, whilst responses of the tropical stingless bee Tetragonula iridipennis differed, suggesting that resource partitioning could be a determinant of spontaneous colour preferences. Reward on an unsaturated yellow colour shifted the bees’ preference curves as predicted, which is in line with previous findings that brief colour experience overrides the expression of spontaneous preferences. We conclude that rather than determining foraging behaviour in inflexible ways, spontaneous colour preferences vary depending on experimental settings and reflect potential biases in mechanisms of learning and decision-making in pollinating insects.
Highlights
The question of how foraging insect pollinators find flowers has intrigued naturalists and scientists for a long time
Bees chose long-wavelength stimuli more when choices to stimuli categorised as either short or long wavelength were compared (χ2 = 9.6, df = 1, p < 0.01; Fig. 4a). Another group of naive A. cerana that were rewarded with sucrose on pale yellow stimuli prior to testing (n = 29) approached the yellow stimulus most (N = 611 choices; sst = 397.72, p < 0.01; Fig. 3b), and bees showed a strong overall preference for long-wavelength stimuli (χ2 = 10.92, df = 1, p < 0.001; Fig. 4b)
As seen for A. cerana, when trained to pale yellow (n = 20), T. iridipennis responded in the tests with a clear preference for yellow (N = 344 choices; sst = 239.20, p < 0.01) and long-wavelength stimuli (χ2 = 22.57, df = 1, p < 0.001;Figs. 3b and 4b)
Summary
The question of how foraging insect pollinators find flowers has intrigued naturalists and scientists for a long time. Given that over evolutionary time, many pollinating insects have become fully or strongly dependent on floral rewards, the adaptive value of such innate preferences for colour and other floral features seems quite obvious. In order to be adaptive innate colour preferences would need to be sufficiently hard-wired ( referred to as genetically determined, or formerly as instinctive (Tinbergen 1951)), in other words expressed regardless of differences in developmental conditions and rearing environment. This means that if insects are to learn by experience, which we know they are capable of, these preferences must subsequently somehow
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
