Cross-modal transfer in visual and nonvisual cues in bumblebees

Abstract

Bumblebees Bombus terrestris are good at learning to distinguish between patterned flowers. They can differentiate between flowers that differ only in their patterning of scent, surface texture, temperature, or electrostatic charge, in addition to visual patterns. As recently shown, bumblebees trained to discriminate between nonvisual scent patterns can transfer this learning to visually patterned flowers that show similar spatial patterning to the learnt scent patterns. Bumblebees can, therefore, transfer learnt patterns between different sensory modalities, without needing to relearn them. We used differential conditioning techniques to explore whether cross-modal transfer of learnt patterns also occurred between visual and temperature patterns. Bumblebees that successfully learnt to distinguish rewarding and unrewarding temperature patterns did not show any preferences for the corresponding unlearnt visual pattern. Similarly, bumblebees that learnt visual patterns did not transfer these to temperature patterns, suggesting that they are unable to transfer learning of temperature and visual patterns. We discuss how cross-modality pattern learning may be limited to modalities that have potentially strong neurological links, such as the previously demonstrated transfer between scent and visual patterns. Electronic supplementary material The online version of this article (10.1007/s00359-019-01320-w) contains supplementary material, which is available to authorized users.

Floral Humidity in Flowering Plants: A Preliminary Survey

“…Some floral traits are difficult for humans to identify but nevertheless influence floral function, or are detectable to floral visitors (Baker, 1977;Clarke et al, 2013;Harrap et al, 2017Harrap et al, , 2019Lawson et al, 2018;Patiño and Grace, 2002;Rands et al, 2011;Whitney et al, 2016). Floral humidity is another such trait and is characterized by an increase in humidity relative to background levels in the space around the flower.…”

Floral temperature patterns can function as floral guides

“…Lawson et al (2017a) found no additional effects of multimodality on reward search time even though both unimodal visual and scent guides alone influenced reward search time. Recent research has found scent and temperature patterns to interact differently with visual patterns Harrap et al 2019), hinting that spatial information from visual and scent patterns may be processed together in the bumblebee's brain, while temperature patterns appear to be processed separately from visual patterns. Such differing interactions between modalities may explain the differing effectiveness of different multimodal guides.…”

“…Temperature patterns corresponding with reward location were generated using heating elements placed on the underside of the flower, following a similar design to Harrap et al (2017Harrap et al ( , 2019. Two kinds of temperature patterns were used, identified here as 'Hot' or 'Warm' (Fig.…”

“…A preference for elevated temperature may attract pollinators to the warmer regions of flowers. Floral temperature patterns, where specific parts of the flower show elevated temperature compared to the rest of the flower, appear to be a common phenomenon (Rejšková et al 2010;Dietrich and Körner 2014;Harrap et al 2017Harrap et al , 2019. This combination of both distinct thermal patterning in flowers and pollinators showing both an ability to detect and a preference for warmer regions of a flower suggests that temperature patterns may be able to lead pollinators to floral rewards when the elevated temperature is localized to reward location.…”

“…Temperature patterns may therefore function as a non-visual floral guide. Bumblebees are also able to learn floral temperature patterns (Harrap et al 2017(Harrap et al , 2019, so temperature patterns may allow further improved flower handling with experience.…”