Insect Forces

The maximum forces measured were 29 mN for honeybees (A. mellifera), 90 mN for bumblebee queens, and 59 mN for bumblebee workers (Bombus terrestris); thus, our data indicate that the maximum forces exerted by midsized bees and bumblebees during a flower visit range between 20 and 100 mN. According to the current state

FIGURE 6.7 A and B show schematic drawings of a longitudinal section of a flower, showing one stamen (style and ovary not drawn). (A) S. glutinosa, and (B) S. sclarea. C and D show force-distance diagrams of the movement of a metal sensor (sensor diameter 0.6 mm) in a flower: (a) sensor touches lever, (b) lever released, (c) sensor touches internal barrier, and (d) sensor touches bottom of the corolla tube. (C) S. glutinosa flower; left: releasing and passing the staminal lever, right: passing the internal ring of hairs. (D) S. sclarea flower.

FIGURE 6.7 A and B show schematic drawings of a longitudinal section of a flower, showing one stamen (style and ovary not drawn). (A) S. glutinosa, and (B) S. sclarea. C and D show force-distance diagrams of the movement of a metal sensor (sensor diameter 0.6 mm) in a flower: (a) sensor touches lever, (b) lever released, (c) sensor touches internal barrier, and (d) sensor touches bottom of the corolla tube. (C) S. glutinosa flower; left: releasing and passing the staminal lever, right: passing the internal ring of hairs. (D) S. sclarea flower.

of knowledge, the bee flowers that are the hardest to trigger are those of L. latifolius, which require forces of 100 mN to be triggered [16]. Therefore, we hypothesize that even large bees do not exert forces that significantly exceed 100 mN during flower visits. The forces bees and bumblebees can exert on flowers are much larger than the weight forces that correspond to their body mass [16]. For example, in the tested bumblebee workers that can exert forces up to 59 mN (mean force measured: 24.6 ± 14.8 mN), a mean body mass of 199 ± 42 mg (n = 56) is found. This means bumblebees can produce a maximum force that is about 30 times their weight force (a mass of 199 mg induces a weight force of 1.95 mN).

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