Collection of nectar by bumblebees: how the physics of fluid demonstrates the prominent role of the tongue's morphology

Abstract

Bumblebees use their tongue to feed on flowers with a mopping-squeezing mechanism. From a comparison of biological data with predictions of a physical model for viscous dipping, we demonstrate that nectar is trapped in the tongue micro-structure.

Essential role of papillae flexibility in nectar capture by bees

“…Repeating this experiment at various sugar concentrations, cs, shows that the lapping rate is essentially constant (Fig. 1C) with a lapping time T L 0.2 s in agreement with previous measurements on various bee species (11)(12)(13)(15)(16)(17)(18). For each concentration considered, the ingestion rate is obtained and reported in Fig.…”

“…10, and ρ l = (1,175 ± 175) kg/m 3 is used (SI Appendix). The immersion length, L I , of the tongue is varied proportionally to the tongue length, L T , for each species [L I (0.6 L T − 1) mm]: L I = 3.2 ± 0.1 mm (Melipona fuliginosa, L T = 7.0 mm), L I = 2.2 ± 0.1 mm (Apis mellifera, L T = 5.4 mm), L I = 2.0 ± 0.1 mm (Bombus, L T = 5.0 mm), and L I = 1.2 ± 0.1 mm (Melipona marginata, L T = 3.8 mm) (12,14). The theoretical curves for Melipona fasciata and Melipona compressipes (L T = 5.9 mm) are close to the one for A. mellifera and are not shown for clarity.…”

“…At very large sugar concentrations, we found that viscous forces impede the full opening of papillae, reducing the amount of nectar collected. (14), and Bombus (11,12) as a function of the sugar concentration. The viscosity in millipascals second at 20 • C/30 • C is also indicated on the top axis.…”

“…The viscosity in millipascals second at 20 • C/30 • C is also indicated on the top axis. The parameter values used are T L = 2T R = (0.20 ± 0.02) s (11)(12)(13)(15)(16)(17)(18), dm = L sin(π/4) (16,(18)(19)(20), and E = (1.1 ± 0.1) MPa for all species; R G = (50 ± 5) µm, R = (2.9 ± 0.1) µm, and L = (170 ± 5) µm (19,21) for Melipona and Apis; and R G = (95 ± 5) µm, R = (2.1 ± 0.1) µm, and L = (135 ± 5) µm for Bombus. The value of E is comparable with the Young modulus of the tip of the adhesive tarsal setae of beetles (22,23) or of the lepidopteran proboscis (24) (discussion is in SI Appendix).…”

Nectar Feeding by a Honey Bee’s Hairy Tongue: Morphology, Dynamics, and Energy-Saving Strategies

“…The majority of flower-visiting insects, including bees, wasps [ 1 , 2 ], flies [ 3 ], butterflies [ 4 ], moths [ 5 ], and some beetles [ 6 , 7 ], obtain nutrition from floral nectar and pollen from flowering plants [ 8 ]. The honey bee ( Apis mellifera ligustica ) is a typical pollinator in the world [ 9 ].…”