Thermoelectric conversion and specific heat of hornet combs

Social wasps belonging to sub-family Vespinae (Hymenoptera) build brood combs made up of hexagonal cells, all of which have their outlet facing in the direction of the gravitational force. These combs are built of organic and/or mineral matter, each grain of which is enwrapped in saliva secreted by the building hornets. The enwrapping hornet saliva hardens rapidly into a tough polymer that binds together the building materials collected from the surroundings. The combs are intended to rear the brood from egg to imago. The comb cell walls possess electric properties which in part have already been elucidated. It has been established that the cell walls behave like a thermoelectric material in that with rise in temperature between 20-30°C there is increase of the electric current from 0 to 150 nano amperes (nA). Additionally, the specific heat of the comb has been measured and was found to be (in the range of 20-70°C) 0.72-0.85 J/g.K. For comparison purposes, analogous measurements were taken from the silk produced by the pupating larva inside each brood comb. The specific heat of the silk was found to differ markedly (two times higher) from that of the cell walls, while the electrical charge of the cell wall is higher than that of the silk cap by more than one order of magnitude The possible reason(s) for this disparity is discussed.