Interspecific variation in beeswax as a biological construction material.

Beeswax is a multicomponent material used by bees in the genus Apis to house larvae and store honey and pollen. We characterized the mechanical properties of waxes from four honeybee species: Apis mellifera L., Apis andreniformis L., Apis dorsata L. and two subspecies of Apis cerana L. In order to isolate the material effects from the architectural properties of nest comb, we formed raw wax in to right, circular cylindrical samples, and compressed them in an electromechanical tensometer. From the resulting stress-strain curves, values for yield stress, yield strain, stress and strain at the proportional limit, stiffness, and resilience were obtained. Apis dorsata wax was stiffer and had a higher yield stress and stress at the proportional limit than all of the other waxes. The waxes of A. cerana and A. mellifera had intermediate strength and stiffness, and A. andreniformis wax was the least strong, stiff and resilient. All of the waxes had similar strain values at the proportional limit and yield point. The observed differences in wax mechanical properties correlate with the nesting ecology of these species. A. mellifera and A. cerana nest in cavities that protect the nest from environmental stresses, whereas the species with the strongest and stiffest wax, A. dorsata, constructs relatively heavy nests attached to branches of tall trees, exposing them to substantially greater mechanical forces. The wax of A. andreniformis was the least strong, stiff and resilient, and their nests have low masses relative to other species in the genus and, although not built in cavities, are constructed on lower, often shielded branches that can absorb the forces of wind and rain.