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First published online December 1, 2006
Journal of Experimental Biology 209, 4901-4907 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02593
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Mechanics of nectar feeding in the orchid bee Euglossa imperialis: pressure, viscosity and flow

Brendan J. Borrell

Department of Integrative Biology, University of California, Berkeley, CA 94720-3140, USA


Figure 1
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  		Fig. 1. Calculated pressure drop versus nectar intake rate for proboscis radii ranging from 0.02 to 0.06 mm. The atmospheric pressure line (broken horizontal line) represents the putative upper limit of the pressure drop that can be developed in the cibarium. The viscous limit line (broken vertical line) represents the most viscous sucrose solution from which orchid bees have been observed feeding.

 

Figure 2
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  		Fig. 2. The relationship between nectar intake rate and sucrose concentration in Euglossa imperialis depends on experimental conditions. Nectar intake rate was measured from trained bees visiting artificial flowers (filled circles) and starved bees accepting sucrose solutions in the laboratory (open circles).

 

Figure 3
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  		Fig. 3. Nectar intake rate depends on nectar viscosity not nectar sweetness in laboratory feeding trials with Euglossa imperialis. Constant sucrose experiment (filled circles): sucrose concentration was held at 25% and solution temperature was maintained 30°C as viscosity was increased to the equivalent of a 65% sucrose solution. Constant viscosity experiment (open circles): viscosity was held at the equivalent of 50% sucrose (10.21 mPa s) and solution temperature was maintained at 30°C as sucrose concentration ranged from 5-50%. Sucrose concentration has no effect on nectar intake rate (F1,28=0.2301, P=0.6352).

 

Figure 4
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  		Fig. 4. Hagen-Poiseuille pressure drop for Euglossa imperialis depends on sucrose concentration (F1,56=9.612, P=0.0030) and ambient air pressure (F1,56=27.06, P<0.0001). Asterisks indicate significant differences.

 

Figure 5
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  		Fig. 5. The fit of a mathematical model of suction feeding (Daniel et al., 1989Go) to measurements from Euglossa imperialis. These data points were measured from starved bees, but were multiplied by a correction factor of 1.39 to be applicable to freely foraging bees. (A) Pressure drop versus sucrose concentration assuming a fixed radius of 0.045 mm; (B) mechanical power output versus sucrose concentration; (C) sucrose intake rate versus sucrose concentration.

 




© The Company of Biologists Ltd 2006