Thermal conductivity of wax comb and its effect on heat balance in colonial honey bees (Apis mellifera L.)

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Wax comb was found to have a thermal conductivity of 0.3610–3 cal/cm sec C. At low air temperatures, honey bees,Apis mellifera L., form clusters inbetween the combs in their nests. The combs provide insulation and the bee behavior actually increases the insulating effectiveness of the combs. When they form a compact living layer over the wax comb, the conductivity can be reduced to 0.06510–3 cal/cm see C. Some aspects of the role of the wax comb in heat balance are examined in this paper.

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... The thermal properties of combs in relation to colonial heat balance, part of the entire energetic equation of a colony, were explored by Southwick (1985). He measured the thermal conductivity of isolated comb and found that while the combs provide insulation, the clustering behavior of the bees actually increases the insulat-ing effectiveness of the combs. ...
... When there is a compact layer of bees on the combs, conductivity can be reduced by an order of magnitude. Given the conductivity of wax combs and bees clustered on and between them, insulation of the combs is the combined effect of combs and the behavior of the bees themselves (Southwick, 1985 (Lee and Winston, 1985;Hepburn, 1986), but in a temporo-spatial framework, comb building only reaches parity with other wax working (capping and repairing) at the height of the colony growth cycle (Muller and Hepburn, 1992). Comb building is conducted in different areas of the nest by many individuals, some clustered in festoons others not, while other wax works are often the efforts of individual bees (Lindauer, 1952). ...
Recent advances in studies of the reciprocal interactions between honeybees and their combs are reviewed. Wax secretion is age-related, varies with season, is unaffected by the queen, juvenile hormone or the corpora allata but is enhanced in swarming. Comb building is enhanced by the queen. Nest structure can be explained as a self-organization process as can the patterns of brood, honey and pollen. The comb and its contents provide gross information to the colony as to crowding and space which affect brood rearing, energy consumption and comb building. Significant chemical and physical changes occur in the wax during comb building and during its subsequent use. Comb mediates pheromonal cues for cell capping, repairs and queen cell construction, nectar forage, colony defense and colony odor. Mechanically, the combs transmit vibrational signals in the waggle dance and recruitment of new foragers. (C) Inra/DIB/AGIB/Elsevier, Paris.
... Previous investigations of thermal, mechanical properties, and composition of bee waxes have focused on Apis mellifera. Several investigations were made to determine melting temperatures of waxes of A. mellifera [6][7][8][9][10] and their thermal conductivity [11]. ...
Colombia exhibits an extraordinarily high species diversity of the subfamily Apinae (honeybees, bumblebees, stingless bees, orchid bees). This fact makes it worthwhile to look for beeswax as biological material produced by these insects and to prove possible applications in technique and human life. We examined for the first time waxes from pollen and honey pots, brood cells, and involucres of different species of the tribes Bombini, Meliponini, and Apini native to South America. Thermal analyses were carried out with a TA Instruments SDT-Q600 and simultaneous differential scanning calorimetry/thermogravimetric analysis with dry nitrogen as purge gas. Temperature scans started at ambient temperature and went up to 120°C. A fourier transform infrared spectroscopy Prestige-21 spectrometer was used to obtain infrared spectra of the waxes. Our results underline that thermal properties and IR spectra of waxes are more similar within the taxonomic groups than between them and are related to the altitude where bees live. This work contributes to the achievement of information that will serve to establish energy mechanisms used by these insects and to set up conservation strategies to protect them.
... Utermark and Schicke (Utermark and Schicke, 1963) and Tulloch (Tulloch, 1980) reported melting transitions between 61 and 63°C for A. mellifera wax using traditional methods. Timbers et al. (Timbers et al., 1977) examined A. mellifera wax with modern thermal analysis methods and found a melting transition that peaked at 68°C, while Southwick (Southwick, 1985) found the thermal conductivity of A. mellifera wax to be 0.36ϫ10 –3 cal·(cm·s·°C) ...
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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 degrees C, DSC analysis of Apis mellifera Linnaeus wax yielded a broad melting curve that showed the initiation of melting at approximately 40 degrees 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.
Because terrestrial ectotherms cannot tolerate intracellular ice, most treatments in the literature that deal with their overwinter survival in habitats where they encounter subzero winter temperatures describe physiological and biochemical adaptations for cold hardiness (Duman, 1982; Storey, 1987;Zachariassen, 1985). These include freeze tolerance and freeze avoidance, usually by mechanisms employing cryoprotectants (glycoprotein or polyols in the hemolymph), supercooling by removal of ice-nucleating agents, or dehydration (Storey, 1987; Sømme, 1982). All insects occupying regions where winters are long and often severe, overwinter in a diapause phase of development such as a pupa, egg, or resistant larva, as an inactive adult with antifreeze protection, as a resistant egg stage tolerant of desiccation and low temperature, or as freeze-tolerant individuals with cryoprotective agents. A few insect species are successful at migrating long distances to avoid the cold and lack of food.
Experiments during three winters have revealed a metabolism controlling function of bee-induced hypoxia in the winter cluster. Permanent low oxygen levels around 15% were found in its core. This hypoxia was actively controlled, probably via indirect mechanisms. Varying ambient oxygen levels demonstrated a causal relationship between lowered oxygen and reduced metabolic rate (MR). Under deeper ambient hypoxia the bees switched to ultra low MR (ULMR), optional-occasional at 15% oxygen, obligatory at 7.5% oxygen. This dormancy status resembled deep diapause in insects. It stayed reversible after at least several days, and was terminated under normal oxygen at 15°C. Reduced MR via core-hypoxia is essential in water conserving thermoregulation of the wintering cluster. It allows bees to reconcile warm wintering in alert state—for defence of stores—with energy saving and longevity. Two further hypotheses discussed are that winter MR of bees might be related to insect diapause, and that in-body hypoxia might be functional in insect diapause.
1.1. The socially organized honey bees (Apis mellifera L.) gather together in clusters and cooperatively function in homeothermy under conditions of cold stress.2.2. When gathered in large clusters, bees maintain a central core temperature of 34°C even during exposure to extreme cold air temperatures down to −80°C.3.3. Cold-induced heat production is an inverse function of group size, with maximum mass-specific values equalling those reported for mammals.
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This experiment was carried out at the Faculdade de Ciências Agrárias e Veterinárias, Campus de Jaboticabal, UNESP, to study the performance of colonies of Apis mellifera established from Africanized –AF– (5 colonies), Caucasian –CA– (5), Italian –IT– (6) and Carniola –CR– (6) sister-queens, fertilized in the air, as well as the concomitant infestation by the mite Varroa jacobsoni; the temperature inside the beehives (TIB); the longevity of the queens; diameter and number of worker-cells; naturally built queen-cells; the acceptability of old and new combs in the central (CP) and lateral positions (LP) of the beehive; the efficiency methods of beeswax extraction (hand pressing, solar melter, steam and drim with burlap sack) in processing new and old combs and opercula and acceptability of smooth beeswax, foundation with different thickness (48, 66 and 77 g) and with the inclusion of paraffin in different proportions (0, 10, 20, 50 and 100%). The CA bees produced more honey; the IT and AF bees reared more brood, and the AF bees stored more pollen. CA, IT and CR hybrids had a more constant performance while the AF bees presented wider fluctuations, a peak of high production during the winter and lower production during the summer. The average infestation index (AII) by the mite V. jacobsoni was 3.29% in the worker pupae while in the adult workers it was 2.47%. There was no difference (P>0.05) in AII among the hybrids. The TIB was not different (P>0.05) among the hybrids (near = 33.7ºC). IT queens presented a higher longevity (8.8 ± 2.9 months) while the CA ones had the lowest life span (2.6 ± 1.6 months). The bees preferred to build the queen-cells nearest to the side of the hives, and the AF bees produced more cells. The period of highest queen-cell production occurred during August and September, 1989. The acceptance of smooth vs. embossed foundation wax was no different (P>0.05) among the hybrids. Diameter and number of cells per 4 cm2 of comb area were also similar. Hybrids did not show any preference (P>0.05) among the thickness tested. Foundation up to 50% inclusion of paraffin was accepted and used for rearing and food stock. Combs at the CP, both the new and old ones, were utilized for rearing purposes (egg-larvae and pupae) and food deposition (honey and pollen). In the LP, the combs were used only for food deposition (honey, and mainly pollen). However, a preference for the old combs was observed pollen. Finally, it was observed that the solar melter is the best way to get wax from the opercula and new combs, and that the hand press is the best method for the old combs or new and old combs.
1.1. Groups of honey bees (Apis mellifera L.) are able to metabolically regulate their central temperature under cold stress. At 2°C, Africanized honey bees in 30 g groups consumed 46.4% more oxygen per unit time holding their core temperatures at 29.0°C compared to European honey bees.2.2. Differences in oxygen consumption increase as group sizes decrease. Regression analysis at freezing temperature showed that the two races attain similar costs of energy balance with the same mass when Africanized colonies contain about 20,000 bees and European colonies contain 16,000 bees (Fig. 1).3.3. Africanized honey bees tested in groups at temperatures of 2°C and −15°C, showed metabolic rates that were 13–109% higher than those of the temperate region honey bees, but at 22.5°C, the cost of energy maintenance was 54% lower.We predict that physiological and behavioral characteristics combined with climatic conditions in North America will limit the northern distribution of nesting Africanized honey bees to a 120 consecutive day isoline of temperatures not exceeding 10°C during Winter (Fig. 2). In some southern regions of the USA, the Africanized race will have competitive advantage over the European honey bees now extant.
1.1. In late winter, oxygen consumption of honey bee (Apis mellifera L.) clusters showed marked 24-hr periodicity, even when held under constant temperature conditions.2.2. Minimal rates of metabolism (as low as 3.4 w kg −1) were usually reached at night (ca. 0500 hr), and maximum rates (as high as 33.5 w kg−1) in midday (ca. 1400 hr).3.3. Colonies with brood showed less excursion in daily metabolic rate, by maintaining higher night-time levels.4.4. There is a pronounced decrease in metabolic rate for the intact cluster of 9480–23,394 bees from the rates reported for individuals or small groups of bees.
1.1. Thermal conductance (C measured in cal.g−1 hr−1 °C−1) in birds, mammals and lizards is exponentially related to body weight (W measured in g). The equation developed for thirty-one species of birds is log C = 0·662 − 0·536 log W while the relationship for twenty-four species of mammals is log C = 0·691 − 0·505 log W. There is no significant difference between these curves.2.2. Conductance of varanid lizards is ten times higher than for intact birds and mammals and four times higher than defeathered birds. The high conductance of lizards is partly because measurements were made in an air stream up to 300 cm/sec and because of their large skin surface.3.3. Heat loss in defeathered birds is two to three times higher than in intact birds. The greatest increase in conductance occurred in the larger birds, suggesting the greater insulation of the large birds partly resides in the feathers.