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First published online December 14, 2007
Journal of Experimental Biology 211, 121-127 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.007583
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The thermal properties of beeswaxes: unexpected findings

Robert Buchwald1,*,{dagger}, Michael D. Breed1 and Alan R. Greenberg2

1 Department of Ecology and Evolutionary Biology and Institute for Behavioral Genetics, University of Colorado at Boulder, Campus Box 334, Boulder, CO 80309-0334, USA
2 Department of Mechanical Engineering, University of Colorado at Boulder, Campus Box 427, Boulder, CO 80309-0427, USA

{dagger} Author for correspondence (e-mail: rbuchwald{at}gmail.com)

Accepted 31 October 2007

Standard melting point analyses only partially describe the thermal properties of eusocial beeswaxes. Differential scanning calorimetry (DSC) revealed that thermal phase changes in wax are initiated at substantially lower temperatures than visually observed melting points. Instead of a sharp, single endothermic peak at the published melting point of 64°C, DSC analysis of Apis mellifera Linnaeus wax yielded a broad melting curve that showed the initiation of melting at approximately 40°C. Although Apis beeswax retained a solid appearance at these temperatures, heat absorption and initiation of melting could affect the structural characteristics of the wax. Additionally, a more complete characterization of the thermal properties indicated that the onset of melting, melting range and heat of fusion of beeswaxes varied significantly among tribes of social bees (Bombini, Meliponini, Apini). Compared with other waxes examined, the relatively malleable wax of bumblebees (Bombini) had the lowest onset of melting and lowest heat of fusion but an intermediate melting temperature range. Stingless bee (Meliponini) wax was intermediate between bumblebee and honeybee wax (Apini) in heat of fusion, but had the highest onset of melting and the narrowest melting temperature range. The broad melting temperature range and high heat of fusion in the Apini may be associated with the use of wax comb as a free-hanging structural material, while the Bombini and Meliponini support their wax structures with exogenous materials.

Key words: Apidae, wax, differential scanning calorimetry, heat of fusion, melting point, thermal properties






© The Company of Biologists Ltd 2008