Fig 1.
Animal used in the experiment.
(A) The right hind leg of the honey bee was chosen for the experiment. (B) Scanning electron microscopy image of the tip of the claw of a honey bee, showing a diameter of 6.8 μm.
Table 1.
Parameters determining the surface roughness of sandpapers.
Fig 2.
Adhesion measurement device developed in this study.
Fig 3.
Forces applied by honey bees on different surfaces.
(A) Box plots of normal force generated by honey bees on surfaces of varying roughness presenting a comparative analysis of the forces generated by honey bees with intact adhesive pads (orange) and those with only claws (green). (B) Box plots of shear force generated by honey bees on surfaces of varying roughness presenting a comparison of the forces generated by honey bees with intact adhesive pads (orange) and those with only claws (green). Statistically significant differences are indicated by ***P < 0.001, **P < 0.01, and *P < 0.05, and n.s. denotes statistically non-significant differences.
Table 2.
Summary of the results of independent t-tests.
Fig 4.
Model for the interaction of the claw tip of a honey bee with surface irregularities.
The gray bumps represent rough basal particles, and the yellow spherical represent the tips of the claws. α, the contact angle, is the angle between the line connecting the centers of the hemispherical particle and the claw tip and the horizontal direction; F, the tangential force generated by the bee’s leg; fN, line running perpendicular to the normal line N running through both centers of the particle and the claw tip; h, the depth of the hemispherical particle embedded in the substrate; r, the claw radius; R, the particle radius; W, the force acting on the claw; P, contact point.
Fig 5.
Conditions necessary for mechanical interlocking.
(A) Dependence of the force ratio F/W (F represents the leg force, and W is the force acting on the claw) on the contact angle (α) at different friction coefficients between the claw and particles of the sandpaper. (B) Dependence of h/R ( represents the immersion depth of the particle, and
is the particle radius) on the contact angle (α) at different values of the relationship R/r (particle radius/ claw tip radius). When the diameter of a particle is comparable to the claw tip diameter (R/r = 1), both structures cannot interlock even at the friction coefficient f = 0.5. When R/r exceeds 5, the structures may interlock even at f = 0.2. The model predicts the relative maximum force depending on the friction coefficient at contact, the diameter of particles, and the immersion depth. Broken lines divide the ranges of α at which interlocking (self-locking) occurs (left side) at a particular friction coefficient value.
Fig 6.
Distribution of fluid bridges between the foot pads of bees and the contact planes.
The green graphic represents the adhesion pad, the gray part is the substrate surface and the blue part is the liquid bridge. (A) Mucus secreted by the foot pads fills the gaps between the rough bodies. (B) Mucus secreted by the footpad does not fill the gaps between the rough bodies. d, the height of the liquid bridge;, the contact angle of the smooth plane; R, the radius of the liquid bridge;
, the effective contact angle; and
, the cape of suspension.
Fig 7.
Measurements of the normal and shear forces applied when the adhesive pad of a bee acts alone.
(A) Measurement of normal force when the adhesive pad acts alone. (B) Measurement of shear force when the adhesive pad acts alone.
Table 3.
Parameter values used for the liquid bridge.
Fig 8.
Relationship between normal adhesion force and liquid bridge height
. n, the scaling factor for the contact area; r, the roughness factor.