Physico-chemical characteristics of waxes produced by the African honeybee, apis mellifera scutellata.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of PhilosophyIn this dissertation the physical and chemical alterations induced by mastication and manipulation of wax by the worker bee in honeycomb construction, and the subsequent contribution afforded the structural integrity of the nest, are elucidated. In comb building, the freshly secreted wax scales are mandibulated together with a frothy salivary emulsion, and added piece-meal to form honeycomb. Textural modifications were revealed using X-ray crystallography. While virgin scale wax is highly structured, with the crystallites aligned approximately perpendicular to the planar surface, comb wax has a random crystallographic arrangement. This reflects a disruption of the crystallite structure following the mechanical insult of mastication. Chemical analyses included investigation of both lipid and proteinaceous elements. Lipid composition was evaluated by enzyme-catalyzed as well as thin-layer and gas-liquid chromatographic methods. The results indicate a reduction in scale diacylglycerols with a corresponding increase in comb saturated monoaeylglycerols. Such modifications are highly suggestive of lipase activity within the salivary addition. The proteins of comb and scale wax were analyzed electrophoretically, under reduced conditions. Each wax possesses unique polypeptide fractions, in addition to sharing common protein species, It is speculated that those in common represent integral proteins, such as transport molecules, while the disparities noted may be due to salivary enzymatic degradation, or even glycosylation. The effects of these textural and chemical alterations on the mechanical behaviour of the waxes was assessed. Tensile tests were performed on a variety of scale and comb wax preparations over the range of temperatures likely to impinge on the honeybee nest. These investigations reveal the specific structural contributions made by each of the physico-chemical alterations described. Further, they demonstrate that while scales are ideal moulding materials due to their high distensibility and low stiffness, the greater resistance to deformation and lower potential for extension makes comb wax a superior structural material. The mechanical advantage for including propolis and cocoon silk within the comb structure was also investigated. Tensile testing indicates that the resultant composite material is structurally superior, largely due to the presence of silk reinforcement.Andrew Chakane 201