Nest Scent & Warmth
In the early 19th century, cabinet maker and beekeeper Johannes Mehring suggested that a bee colony was single creature equivalent to a vertebrate animal. This led to the eventual use of the German term "Bien" to represent that whole organism. Roughly a century later, the American Biologist A M Wheeler coined the term "superorganism" for living forms of this type, where the whole consists of parts which are physically separable but are functionally integrated.
When viewed in this manner, the hive in which a bee colony lives is, in fact, the shell, or skin, of the overall organism. Within that skin exist bees and honeycomb, along with the contents of the comb, larval bees, bee bread (fermented pollen) and honey. But this is not all, there are further components in the form of warmth, scents and moisture. In the 1940’s another German speaking beekeeper, Johann Thür, considered and described in detail these essential unseen components of the Bien. Of the need for warmth, he said: "In order to thrive and produce, bees depend completely on heat. It is as important for them as nourishment." He also recognised the vital role that volatiles, for example from propolis, play in maintaining hygiene within the hive: "This retained heat is a mass of warm air, impregnated with scent, and thus germ-free." He continued "...a deficiency of retention of nest scent and heat calls for significantly increased food consumption and inopportune effort by the bees, and causes the hitherto seemingly inexplicable emergence of particularly infectious diseases…"
A warm home for bees where they are free to create their own comb according to the needs of the Bein. A tree provides massive thermal interia - smoothing out the outside temperature highs and lows.
Thür was not impressed with the effect of modern frame beekeeping and modern bee breeding: "Frames, and the hives based on them, suppress natural comb construction and, with this, the retention of the nest scent and heat. Modern artificial bee breeding has barely any inkling of this." He also quotes approvingly from an article by another beekeeper that: "The combs in hollow trunks of trees … as well as in skeps, are fixed to the walls. Each corridor between the combs forms a closed space, like a room. Thus, in winter, the heat of the cluster cannot flow away through the many gaps between the frames and the hive walls. This avoids not only loss of heat, but also draughts, condensation in the hive and excessive consumption of stores."
Left alone, bees will naturally create in their chosen cavity an environment which maintains this warmth and germ-free atmosphere. Every crevice of the interior of the cavity is covered in wax or propolis to ensure that each pathway between the honeycombs forms a complete room in itself, with an opening below the bottom of the comb to enable fresh air to enter and circulate.
Overwintering bees need to maintain temperatures of around 22 to 25℃, increasing to 34 to 35℃ for the brood nest in summer. All this heat has to be produced by the bees themselves. This requires significant effort - particularly during colder months - and consequently substantial amounts of honey. The better insulated a hive, the less honey is used to keep it warm. This applies even in the summer, when bees ripen nectar into honey by raising the temperature to as much as 40℃. Similar temperatures are reached during the creation of new comb. A well insulated hive takes less honey to reach and maintain these temperatures.
There are hives available, such as the Sun Hive and Warré hives, which take into account the bees need for warmth, scent and germ-free atmosphere to a greater extent than conventional frame-based hives. The thick highly insulating walls in variants of log hives can give even greater levels of heat retention, mimicking the conditions found in natural tree cavities. Bees do well in such hives, but nothing matches a tree! The tree's massive thermal inertia resists day and night temperature fluctuations, while easily retaining the precious heat of the colony.
When it comes to opening hives, regardless of the type, the needs of the bees must again be considered. There are occasions when opening a hive may be considered necessary and appropriate but, every time the beekeeper does so, the warmth and atmosphere within is disturbed. It is good to bear in mind that the health and wellbeing of the Bien, both in breeding and producing honey, depend on the warmth of the nest. Not causing unnecessary stress and extra work in rebuilding hive temperature and atmosphere will contribute to improved colony health in the long term.
Related paper in our science database:
Ratios of colony mass to thermal conductance of tree and man-made nest enclosures of Apis mellifera:
Lüneberg skep over a Warré box with observation window. Note the ends of the comb are attached to the glass, creating closed passageways. The Warré is designed to allow this.
Interior of a Zeidler tree hive showing the long combs typical of a wild or natural hive.
The quoted extracts from Johann Thür’s work are taken from David Heaf's translation, which is available in full here.