Thermal Impacts of Apicultural Practice and Products on the Honey Bee Colony
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Journal of Economic Entomology, 114(2), 2021, 538–546
doi: 10.1093/jee/toab023
Advance Access Publication Date: 11 March 2021
Research
Apiculture & Social Insects
Thermal Impacts of Apicultural Practice and Products on
the Honey Bee Colony
Daniel Cook,1,3, Alethea Blackler,1 James McGree,2 and Caroline Hauxwell2
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Creative Industries, Queensland University of Technology, Brisbane, QLD, Australia, 2Science & Engineering Faculty, Queensland
1
University of Technology, Brisbane, QLD, Australia and 3Corresponding author, e-mail: d9.cook@hdr.qut.edu.au
Subject Editor: David Tarpy
Received 12 October 2020; Editorial decision 26 January 2021
Abstract
Hive design and apicultural processes have not been fundamentally changed since the design and commer-
cialization of the Langstroth moveable frame hive in 1854. Colonies of Apis mellifera Linnaeus (Hymentoptera:
Apidae) (the honey bee) maintain a brood nest temperature within the narrow range of 34.5–35.5°C, crit-
ical for brood development. Apis mellifera invest considerable energy to maintain hive homeostasis through
behavioral modification of the hive environment. Human honey-harvesting processes and removal of the
honey-filled comb (a source of thermal mass) have a detrimental impact on hive temperature that requires
an increased investment of energy to rectify. This additional energy demand on the bees is a form of stress
to the colony and diverts workers away from other essential tasks to that of environmental management. We
investigated the thermal energy loss resulting from the removal and extraction of honey, the rate of thermal
loss of an Australian standard Langstroth 10 frame hive, and the effect of honey and wax as a thermal mass
in unoccupied bee hive. The results demonstrate that considerable energy expenditure would be required to
rectify the hive thermal environment after honey harvesting or honeycomb frame addition. Honey provides
thermal mass in the beehive, acting as a thermal buffer to external temperature change, which may mediate
part of the thermal losses from the simplistic design of the Langstroth hive. Identification of these impacts in
current apicultural practice and hive design allows for the improvement in the design of beehives and asso-
ciated practices. These improvements may reduce stress to the bee colony, increasing colony efficiency for
pollination and nectar foraging.
Key words: bee, hive, apiculture, temperature, Langstroth
Beehive design in the western world has had little developmental moving upwards and fouling the human-farmed honey stock with
iteration since the archetypal inception of the Langstroth hive in eggs and brood (Goodman 2015). Honey supers commonly contain
1852, and the subsequent mass manufacture with world-wide 8–10 wooden frames containing wax comb started from either a
spread (Langstroth 1852). The Langstroth hive consists of a simple molded wax or plastic foundation sheet (Goodman 2015, Quality
wooden box, open at top and bottom, whose measurements vary Beekeeping Supplies 2020). Foundation contains the imprint of
from country to country but are in the range of 505–515 mm long × the hexagonal cell structure (~5.3 mm diameter) and is ‘built out’
376–508 mm wide (external) (Mitchell, 2019, Cushman 2020). Each by the bees that excrete and masticate wax flakes before shaping
hive box has a varying height depending on use and apiarist prac- and applying it to the foundational comb structure (Tautz 2008).
tice, although the brood box is commonly a ‘deep’ box measuring The comb is built out to approximately 15 mm on each side of
238–258 mm high depending on location, with 244 mm favored in the foundation to create a material-efficient comb structure suit-
Australia and the United States (Cushman 2020). able for rearing brood and storing pollen and nectar (Tautz 2008).
The queen lays eggs in the brood box and is excluded from upper Honeycomb is filled with nectar, evaporated to a water contentJournal of Economic Entomology, 2021, Vol. 114, No. 2 539
which either cuts, scrapes, or flails off the wax caps (Goodman (Goodman 2015, Somerville et al. 2018). Stable hive homeostasis
2015). Decapped frames of honey are centrifugally extracted, and provides increased worker availability, resulting in a larger foraging
the remaining empty frame and wax structure are called ‘stickies’ population for pollination or nectar collection (Abou-Shaara et al.
(Goodman 2015). Stickies are either placed back onto the brood box 2013). The thermal impact of standard apiary practices of ‘supering’
for bee facilitated cleaning, repair and refill, or are stored in a cool, boxes of honey on top of the brood nest, opening and inspecting
insect-proof area for later reuse, often a refrigerated room in warmer the colony, and the design of the Langstroth hive have received little
climates. attention from the scientific literature. This study seeks to demon-
Commonly, Langstroth hives are constructed of soft timber such strate the thermal impacts of human apicultural practice on hive
as pine and have a wall thickness of ~23 mm, far thinner than nat- homeostasis.
ural log hives (Mitchell 2019). This thickness of pine has a low in-
sulation value (R = 1.21 for 22-mm hive wall) in contrast to the
newer expanded polystyrene hives designed to aid hive homeostasis Materials and Methods
with a more insulating material (R = 7.9 for 40-mm hive wall; Two experiments were conducted to determine 1) the thermal energy
Australian Honey Bee 2020). This insulation factor is important as contained in Langstroth full-depth super and 2) the role of honey
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Apis mellifera Linnaeus manage temperature and humidity in their and wax as thermal mass within the bee hive. Experiment 2 was
nest (Fahrenholz et al. 1989, Tautz 2008, Mitchell 2019). Hive con- conducted with two configurations of hive, sealed with a hive lid
struction from poor insulating materials causes temperature changes and unsealed by a hive lid. To supplement these two experiments, the
within the hive from external conditions, resulting in worker bees theoretical heat loss of a Langstroth hive was calculated at various
diverting from jobs such as defense, resource gathering, and cleaning external temperatures. All calculations and experiments used an op-
to manage the hive homeostasis (Abou-Shaara et al. 2013). Failure timal brood temperature of 35°C.
to manage nest and brood temperatures within a narrow range The experiments and calculations did not account for the bio-
results in retardation of brood cognitive abilities and a decline in logical mass of the bees or brood which, for a strong colony of
colony health (Tautz et al. 2003, Jones et al. 2005). 40,000–60,000 members may amount up to 6 kg of additional mass,
The nest temperature is maintained through four primary nor did the calculations consider the active heating and cooling be-
methods: heating, cooling, evacuation, and insulation (or thermal havioral mechanisms of the bees.
redistribution). Heating is achieved through the vibration of antag- Maxim Thermochron TC (DS1921G) iButtons (Maxim
onistic thoracic flight muscles in ‘heater bees’, who either press them- Integrated 2020) were used to measure temperature of hive com-
selves against capped brood cells to heat small brood groups or move ponents and ambient temperature in both experiments (±1°C from
into empty cells between brood cells to radiate heat to multiple cells −30°C to +70°C with 0.5°C increments).
simultaneously (Kleinhenz et al. 2003, Tautz et al. 2003, Humphrey
and Dykes 2008, Stabentheiner et al. 2010). Nest (hive) cooling is
Experiment 1: Heat Energy in a Langstroth Super
obtained through the importation and evaporation of water droplets
Six Langstroth full-depth wooden frames containing filled and
along with worker ‘fanning’ behavior to circulate air within the hive
capped honeycomb were weighed and centrifugally extracted of
(Bonoan et al. 2014, Abou-Shaara et al. 2017, Bordier et al. 2017).
honey. Mechanically stripping the frames of wax, the individual
When fanning activity cannot provide sufficient cooling, a portion of
components were weighed, providing weights and ratios of the wood
colony members evacuate the nest and cluster or ‘beard’ on the out-
frames, wax, and honey. Standard, full-depth, medium-weight wax
side of the hive while the fanning process continues (Abou-Shaara
and plastic foundation weights were referenced from commercial lit-
et al. 2017). A final mechanism for mitigating external thermal im-
erature for comparison (http://qualitybeekeepingsupplies.com.au).
pact is that of ‘heat shielding’, a process where bees press themselves
Data for the specific heat capacity (SHC) of each material, along
against the heated areas (such as nest walls) to shield the brood
with values for A. mellifera energy expenditure for hive heating (3.7
comb from the heat, acting as ‘mobile insulation’ (Starks and Gilley
J/min/°C) and wax comb creation, were referenced from literature
1999, Bonoan et al. 2014). This heat-shielding process has been
(Timbers et al. 1977, Tautz 2008). The energy required to heat the
linked to heat redistribution within the hive (Bonoan et al. 2014).
components was then calculated for each 5°C increment from 0°C
Stored honey also plays a role in hive temperature management,
to an ideal brood homeostasis temperature of 35°C. We converted
demonstrating a lower rate of thermal change compared with sur-
energy expenditure into minutes of work for the bee required to
rounding air and storing a measure of heat depending on location in
produce heat, nominally called ‘bee-minutes’.
the hive (Humphrey and Dykes 2008). Many experiments into hive
health, behavior, and colony state have used temperature sensors to
gauge colony homeostasis (Stalidzans and Berzonis 2013, Kridi et al. Experiment 2: Honey and Wax as Thermal Mass
2016, Meikle et al. 2017, Melicher et al. 2019). Temperature sensors To determine the thermal role that honey plays in the hive, honey
are commonly placed either centrally above the brood box or on supers in varying configurations of filled and emptied honeycomb
top of the center frame of the honey super (Stalidzans and Berzonis were placed in a thermally controlled cabinet and subjected to a
2013, Zacepins et al. 2016, Meikle et al. 2017). Locations often ap- range of 24-h thermal patterns. We conducted tests to determine the
pear to be chosen for centrality in the hive box geometry rather than rates of heating and cooling of filled, extracted, and foundation-less
based around colony composition and the architecture of brood frame configurations.
nest, honey, and pollen stores. These temperature-based experiments A standard Langstroth full-depth super made of painted
have been correlated to swarming activities, development periods, Australian kiln-dried hoop pine was filled with 10 frames of
thermal stress, and colony health (Zacepins et al. 2016, Meikle honey-filled and capped comb. The super was placed on a standard
et al. 2017, Melicher et al. 2019). Change in hive homeostasis from Langstroth baseboard (with opening) and a drip tray beneath in case
human colony manipulation or supering practice (the addition of a of honey leaks. The hive was placed in a temperature and humidity-
honey box onto the colony) can chill the brood, causing increased controlled cabinet maintained at 60% relative humidity, while the
mortality, susceptibility to disease, and reduced foraging activity temperature was varied. The cabinets were cycled through 24-h540 Journal of Economic Entomology, 2021, Vol. 114, No. 2
temperature simulations with periods of 12 h at each temperature lid) and 2) all expanded polystyrene to provide an indicative heat loss
and rapid (cabinet maximum rate) transition between temperatures. rate. Hive body wall thickness was 22 mm with a hive lid thickness
Maxim iButtons (Maxim Integrated 2020) took temperature of 9 mm. Heat loss calculations based on 1D conduction used the
readings at 10-min intervals. iButtons were embedded into the wax areas of the four sides and the lid of the hive, omitting the baseboard
comb immediately under the center of the wooden top bar of the as convective heat rise was assumed, and also assuming that all sides
frame in both the full honeycomb and extracted comb. An additional and the roof of the hive are exposed equally to uniform internal
iButton was placed on top of each frame as shown in Fig. 1a. temperatures. The calculations ignored clustering, fanning, and in-
In configuration 1, five frames of filled and capped honey (n = 5), sulation behaviors of the occupants and external environmental fac-
and five centrifugally extracted frames were used (n = 5), with the hive tors such as wind, rain, and sun acting on the hive. Thermal loss
sealed at the top using a 9-mm plywood (pine) lid similar to those used calculations used Fourier’s law of heat conduction with thermal
in the industry. Three repetitions of 4–40°C temperature cycles were conductivity of hoop pine (0.140 W/mK), Masonite (and expanded
used to establish maximum cabinet heating and cooling rates. The polystyrene; 0.03 W/mK), and expanded polystyrene taken from lit-
cabinet was then cycled for three repetitions at 12 h per temperature erature (National Construction Code 2019, MBSales.com.au 2020,
point between 15 and 35°C to mimic thermal changes in Brisbane, EngineeringToolbox.com 2021). Calculations used arbitrary 5°C in-
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Australia mean spring temperatures, or the summer temperature in crements increasing to the ideal internal hive temperature of 35°C.
more temperate climates (when super addition typically occurs).
In configuration 2, five frames of filled and capped honeycombs
(n = 5) and five frames of centrifugally extracted ‘stickies’ (n = 5) Results
were used without a plywood lid to hasten heating and cooling. Experiment 1: Heat Energy in a Langstroth Super
Several repetitions of three temperature sets were performed: 5–35, The component weights and percentage ratio of Langstroth full-
15–35, and 25–35°C, representing the change from an arbitrary am- depth frames were calculated (n = 6) with SD. The average frame
bient condition to those of the 35°C maintained colony interior. weight was 2.98 kg, with an SD of 0.31 kg. The wooden frame com-
ponent made up 6.8% of the total mass, with an average weight of
Theoretical Thermal Loss of a Langstroth Hive 0.2 kg. Honey was 74.5% of the total weight at 2.23 kg per frame.
We calculated the rate of thermal loss from a single Australian The remaining weight was made up of the wax comb and a small
(and American) standard, 10-frame, full-depth ‘super’ (406 × 508 × proportion of residual honey from the centrifugal extraction pro-
241 mm) constructed of 1) kiln-dried hoop pine (with a Masonite cess that made up 18.7% at 0.55 kg per frame. The manufactured
wooden frames demonstrated the lowest weight variation, followed
by wax with a variation of ±0.39 kg and honey with a variation of
±0.98 kg.
The total weight of a supers’ components (not including the box
itself, the super body) was calculated at 29.98 kg. Individual com-
ponent weights of an average 10 frame supers were calculated as
22.3 kg of honey, 5.5 kg of wax, and 2 kg of wooden framework.
The SHC of honey (2,260.44 J/kgC), wax (2,026 J/kgC), wood
frames (2,500 J/kgC), and the supers’ volume of air (1,006 J/kgC)
was used to calculate the energy required to transition the contents
of the super from one temperature to another. The super body was
omitted from the calculations due to its thermal gradient to the am-
bient temperature. Energy calculations used the formula:
q = cm∆t,
where q = heat energy, c = specific heat, m = mass of substance, and
Δt = change in temperature.
For supers containing extracted frames, this resulted in 487 kJ
of energy required to heat a super stored at 5–35°C, 324.8 kJ of en-
ergy required to heat a 15°C super to 35°C and 162.4 kJ of energy
required to heat a 25°C super to 35°C.
When considering variations on practice of super addition in the
apicultural industry, these calculations were also performed with
‘virgin’ comb foundation materials such as wax foundation and
plastic foundation, resulting in the heat energy required for various
configurations, as shown in Fig. 2.
To provide a measure of impact on the bee colony the energy
expenditure rate of a bee during heating processes was used (3.9 J/
min; Tautz 2008) to calculate the time required (in bee-minutes) to
return a new super to optimal hive temperature, as shown in Table 1.
The amount of wax comb that is constructed on virgin wax and
plastic foundation was calculated through subtraction of virgin
Fig. 1. (a) iButton positions on single, full-depth frame. (b) Maxim iButton foundation weight from extracted honeycomb weight providing a
placement in a full-depth super of 10 frames. Frames are central to each weight of 4.15 kg (plastic) to 4.87 kg (wax) of built comb across
group of either five filled comb frames or five extracted comb frames. 10 frames at 78.45 kJ per gram energy investment (Tautz 2008).Journal of Economic Entomology, 2021, Vol. 114, No. 2 541
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Fig. 2. Energy required to heat an added super of different frame configurations to a hive temperature of 35°C. Mass of the frame configuration relates closely
to energy required to heat the frame. Error bars indicate SEM in weight measurements. Plastic foundation and the wooden frames had the smallest weight
variance resulting in very small SE.
This results in a substantial energy investment of 381.9 MJ (wax) In contrast to configuration 1 thermal rate of change, configur-
and 325.7 MJ (plastic) to build out virgin foundation. Comb recti- ation 2 (no lid) super demonstrated faster losses and gains of heat
fication, capping, and new comb building on extracted stickies were energy compared with the ambient temperature change (Fig. 3). This
not calculated due to the highly variable nature of damage occurring indicates advantages in the use of well-fitting hive-ware with in-
during the extraction process and return of the frames to the hive. trinsic sealing capabilities.
Full frames of capped combs heating energy requirements were cal-
culated as a reference point for thermal energy stored within the
Thermal Loss of a Langstroth Hive
honey and its supporting comb in the hive.
Measurements of a standard Langstroth hive were made and found
Although the addition of virgin foundation of either type re-
to correlate with standard Australian (and American) full-depth
duces the energy required to heat the super and contained frames,
10 frame supers. The supers were 416 mm wide × 508 mm long
it is worth noting that the energy required to construct fresh wax
× 241 mm high with a body thickness of 22.5 mm. Body area cal-
comb on the foundation is an order of magnitude higher than the
culations omitted thicker corner join sections and lid to body wall
heat energy required to heat the stickies with their higher wax
thicknesses to maintain single-dimensional thermal transmission,
mass.
but treated joins as single-thickness areas. Total body wall area was
0.424 m2, and roof area was 0.171 m2.
Experiment 2: Honey as Thermal Mass Rate of thermal loss (conductive heat transfer) was calculated
Configuration 1 (lidded super) thermal tests demonstrated a signifi- using Fourier’s law:
cant thermal buffering effect of the filled honeycomb frames within
the super (Fig. 3), and the release of heat upwards to the top of Q = (k/d)A ∆t,
the frame, most likely through convection processes. The extracted where Q = rate of thermal loss in Joules per second (Watts), k = ma-
comb followed the ambient temperature closely, losing heat rapidly, terial thermal conductivity, d = material thickness in meters, A = area
possibly due to the large surface area of the comb structure, and in square meters, and Δt = temperature differential.
exhibiting less of the convection processes compared with the filled Heat loss was calculated for a single, full-depth, 10 frame
comb. Heating and cooling of the filled comb within configuration 1 brood box with lid (super) in two configurations; radiata pine body
(lidded) super demonstrated a far slower rate of change of 4% of the (across the grain; 0.14 W/mK) with a Masonite lid (0.12 W/mK)
ambient environmental temperature change (Table 2). and all expanded polystyrene (0.03 W/mK; MBSales.com.au 2020,542 Journal of Economic Entomology, 2021, Vol. 114, No. 2
Table 1. Colony expenditure (bee-minutes) to bring hive to 35°C
Honey super starting temperature, °C
Colony rectification (bee-minutes) 0 5 10 15 20 25 30
Virgin wax foundation 57,260 49,080 40,900 32,720 24,540 16,360 8,180
Plastic foundation 61,462 52,681 43,901 35,121 26,341 17,560 8,780
Extracted comb 145,776 124,951 104,126 83,300 62,475 41,650 20,825
Filled, capped comb 610,267 523,086 435,905 348,724 261,543 174,362 87,181
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Fig. 3. Extracted versus filled honeycomb during 24-h, cycled thermal tests. The experiment was repeated three times, and results were averaged across repeats.
EngineeringToolBox.com 2021, Woodproducts.fi 2021). Roof heat mimicking standard apicultural practice. By calculating the energy
loss was calculated for an expanded polystyrene lid and a commer- required to heat the super from varying starting temperatures to
cially available 9-mm Masonite lid (0.12 W/mK; MBSales.com.au an optimal brood temperature of 35°C, and the activity required
2020). A 10°C difference between internal (35°C) and external tem- to do this expressed as ‘bee-minutes’, it can be shown that adding
peratures (25°C) was calculated resulting in 49.3 W losses in the a suboptimal temperature super onto an active hive causes signifi-
wooden hive and 11.4 W losses in the polystyrene hive (Fig. 4). The cant time and energy expenditure by the colony. This likely reduces
polystyrene hive was calculated to have 23% of the thermal losses of foraging for both nectar and pollen until the temperature and hive
the wooden hive of the same thickness. homeostasis are restored. When considering local area average tem-
peratures, we can see that timing and consideration of weather
factors, such as sunny, windy, warm, or cool days may have con-
Discussion siderable productivity impacts on the bee colony. Figure 5 demon-
Specific heat capacities were obtained and used to calculate heating strates the application of this in SE Queensland, Australia, using
requirements for empty wooden frames, wax comb, and honey monthly mean high and low temperatures and comparing the en-
using experimentally confirmed weights and ratios. These fig- ergy expenditure required to heat a super stored at the environ-
ures were used to calculate the energy required to heat configur- ment temperature to the optimal colony temperature (Australian
ations of supers containing frames of virgin foundation, extracted Government Bureau of Meterology 2018). Placing a super on a
comb (stickies), and filled comb as applied on top of a brood box, brood box on a warmer day rather than a cool day may save twoJournal of Economic Entomology, 2021, Vol. 114, No. 2 543
Table 2. Rate of thermal change of full and extracted frames of comb in sealed and unsealed supers
Honeycomb frame rate of thermal change in sealed and unsealed boxes of comb (°C/h)
Filled comb Extracted comb Ambient
Heating Cooling Heating Cooling Heating Cooling
Unsealed super 5.5 −3.5 10.88 −11.75 21 −22.5
Sealed super 0.75 −0.75 11.5 −13 21.25 −21
Percentage of ambient rate of change
Filled comb Extracted comb
Heating Cooling Heating Cooling
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Unsealed super 26 16 52 52
Sealed super 4 4 54 62
Thermal change was calculated as degrees Celcius per hour from the averaged data of three repeats. Of note is the high level of thermal buffering provided by
the filled, capped honeycomb in both the sealed and unsealed supers.
Fig. 4. Theoretical heat loss to the external environment from ideal colony temperature in two material types of Langstroth hive, wood, and expanded
polystyrene. Wall and roof thicknesses remain the same between hives.
to three times the energy required to bring the super to tempera- to ambient temperature or even heating them before placement on
ture. Commonly, extracted comb frames are kept in cold rooms to the brood box could increase the colony’s productivity by tens of
prevent wax moth, ants, and small hive beetle causing damage to thousands of bee-minutes.
the comb during storage and later infecting hives. Supering brood Lower thermal impacts were demonstrated using virgin wax
boxes with cold comb that has been stored at 2–5°C can cause the or plastic foundation rather than extracted comb; however, the
expenditure of between 130,000 and 145,000 bee-minutes in re- long-term energy deficit to produce new wax far outweighs the
heating. A small change to this practice of allowing supers to warm thermal benefits. Therefore, the optimal introduction of foundation544 Journal of Economic Entomology, 2021, Vol. 114, No. 2
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Fig. 5. South-East Queensland, Australia monthly mean high and low daytime temperatures versus related energy required to heat super from those
temperatures (Australian Government Bureau of Meterology 2018).
frames should be gradual and in conjunction with previously ex- condensation and moisture (Sudarsan et al. 2012). This hypothesis is
tracted comb so as not to overly impact colony productivity, al- contrary to the somewhat common practice of using ventilated hive
though this would likely reduce apiarist efficiency. Small changes to lids (originally intended to prevent overheating during vehicular hive
practice, such as warming supers before supering operations, may migration; Goodman 2015) that release warm air from the top of the
produce significant productivity benefits over time and may be an hive and may decrease circular convective airflow in favor of ver-
area for future experimentation. Further to this, when preparing tical, chimney-like flow through the hive. Our results demonstrate
hives for pollination or activities where maximum colony effort that hives without lids (vertical air flow) release stored heat energy
is required, it can be recommended that warmed extracted comb far faster than sealed hives (convective flow), suggesting ventilated
(stickies) be used in place of foundation for maximum colony lids decrease the efficacy of stored honey as thermal mass, effectively
output. The process of removing full honeycomb from the hive, cooling the hive by drawing external air in and venting the warm
colloquially known as robbing, causes the loss of considerable moist air through the lid. This implies the need for a redesign of the
thermal mass in the colony reducing the internal thermal stability. ventilated lid to optimize the colony’s use of this thermal mass. In
Filled honeycomb loses heat at just 4% the rate of the ambient natural log hives, Mitchell (2016) describes the colony’s inclination
air and releases heat upwards into the hive. This slow release and to move upwards to take advantage of the thermal gradient as the
absorption of heat provide a measure of thermal hysteresis (a lag weather cools; however, the inclusion of a queen excluder under the
in changing physical property) within the hive, possibly mitigating super would prevent the colony from taking advantage of this gra-
the effects of transient weather conditions such as rain or wind. dient. Earlier apicultural processes used ‘nadiring’ (placing a honey
The storage of honey in the frames closest to the walls of the hive box under the brood box rather than on top) to take advantage of
may serve to reduce colony heat loss or gain through thermal buf- this thermal gradient, allowing the bees to benefit from the warm
fering of the external ambient temperature from the poorly insu- comb in the lower box. However, due to ease of honey removal
lated hive walls. The loss of this thermal mass from honey removal from the top of a hive and the incompatibility of queen excluders
is exacerbated by the practice of placing a suboptimal temperature in providing drone passage to a bottom entrance from a top-box
super in its place, causing considerable energy output reheating brood nest (causing drones to remain trapped by the excluder), api-
the super. In the context of migratory pollination, where a drop in arists seem to have rejected this process in favor of process efficient
colony temperature is observed during transport (Ahn et al. 2012), supering. This indicates that colony stress from external weather
the provision of full frames of warmed capped honey or an in- conditions could be reduced through the removal of the queen ex-
crease in the hive body’s thermal mass may mitigate the chilling cluder or the move to a nadiring practice with a redesigned hive
of the colony. entrance (for drone passage) when entering cooler months of the
In a sealed hive, the release of heat into rising warm air creates year. These changes in operational hive layout indicate a need for a
a thermal gradient from hive top to bottom (Humphrey and Dykes redesign of the hive entrance and the use of the queen excluder in the
2008, Mitchell 2016). The thermal gradient of warm honeycomb Langstroth hive to accommodate the separation of the queen from
and cool hive walls causes a convection current that aids in air- the honey frames and efficient honey super removal, while allowing
flow, removes CO2 from the brood nest, and likely aids reduction of the colony use of the thermal gradients within the hive.Journal of Economic Entomology, 2021, Vol. 114, No. 2 545
Tautz (2008) describe the continuous expenditure of 20 W of gradient usage. Given the lack of iterative product-process
heat energy by the bee colony to maintain brood temperature. change in apiculture and a lack of integration of scientific know-
Our thermal calculations into heat loss suggest this figure may ledge into practice and products, both hive design and apicul-
be higher if the colony maintains a uniform micro-environment tural practices may be readily enhanced, reducing colony stresses
that is greater than ~10°C above external ambient temperature. and increasing hive productivity for both honey production and
However, our calculations did not consider the localized clus- pollination services.
tering of the brood nest with associated cooling and convection
patterns, as shown by Sudarsan et al. (2012), indicating that References Cited
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