Abstract
Unlike most other bees, the long-tongued orchid bees ingest nectar using suction feeding. Although long tongues allow exploitation of flowers with deep spurs, the energy intake rate is optimal at 10–20% lower nectar sugar concentrations compared to that of lapping bees. This constraint might be compensated by a higher digestive throughput. Additionally, orchid bees might evaporate water from regurgitated droplets of crop contents. We found male Euglossa championi (n = 10) and Euglossa dodsoni (n = 12) to regularly regurgitate droplets of crop content to the base of their proboscis, generating a fluid film between the proximal parts of the galeae, glossa and labial palps. Rhythmic movements of the proboscis may help to increase convection. There was a significant change in sugar concentration between the initially imbibed solution and the resulting crop content (P<0.05) and the time individual bees had engaged in this liquid exposure behavior was positively correlated with the resulting crop sugar concentration. Female Euglossa townsendi and Euglossa viridissima showed the same behavior. Additionally, they manipulated their nectar-enriched pollen provisions for extensive periods of time before deposition in brood cells. The deposited pollen loads (n = 14) showed a significantly higher sugar concentration than the sugar-water available to the bees (P<0.001). Thus, both male and female euglossines show behaviors that promote evaporative water loss from nectar. We suggest that the behaviors have evolved in concert with suction feeding on dilute nectar from deep floral tubes.
Highlights
Carbohydrates in form of nectar sugars constitute the main energy source for adult bees [1], [2]
This could be especially beneficial for activities that require high energy expenditure over reasonably long periods of time, when either access to flowers is not possible, or the time is required for other behaviors This can be envisioned to apply in the context of mate-finding, e.g. during mating flights in carpenter bees [10] or bumble bees [11], where males stay airborne for long periods of time, or when defending a territory
In this study we describe a behavior of euglossine bees dubbed ‘tongue flicking’, which differs from the nectar dehydration practiced by other bees
Summary
Carbohydrates in form of nectar sugars constitute the main energy source for adult bees [1], [2]. A high sugar to water ratio of crop content means that the carried weight has more energetic value, which would allow the bees to remain active and airborne for longer periods of time without having to refuel at nectar sources. This could be especially beneficial for activities that require high energy expenditure (flying/hovering) over reasonably long periods of time, when either access to flowers is not possible, or the time is required for other behaviors Other situations in which bees should benefit from energetically rich crop contents are fast long range movements and when female bees forage for pollen at plants that do not provide nectar (see [13])
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