First, sorry for not yet commenting on your earlier post on survey results.
It's on my to-do list...
To "advantages of warm hives" Derek Mitchell (the expert everyone quotes) would
add "vastly less fuel needed to maintain optimum humidity / temp for honey
manufacture in summer". Ie it's not that they are WARM hives but WELL INSULATED
and it helps in all seasons.
Re: disadvantages. Through the windows I've sometimes seen bees in a loose
cluster with some wandering around comb when the books say they should all be
in a tight cluster. Presumably that uses more energy than simply clustering,
but I'm guessing not much more as the bees seem to thrive in well insulated
hives, and they never seem to use as much winter stores as the BBKA say they
need (maybe 5-7kg not 20kg). Also in general I would say the bees I see have
relatively small winter clusters, nothing near the size you hear of in
conventional books (a winter cluster covering several frames). So despite the
brood rearing being earlier / easier than in a cold hive, one can say "it
works".
A minor advantage of Warres is that OSR honey is said to still be liquid after
2 years, i.e. easily eaten by the bees, instead of crystallising in weeks and
this is thought to be due to the honey being kept continuously warm.
Perhaps the most telling experimental proof of warm hives' benefits is that
Gareth reckoned his bees struggled in TBHs but thrived when he switched to
Warres. He knows his stuff and has lots of hives. Warres are definitely better
insulated than TBHs, but they differ in other ways too (vertical structure vs
horizontal) so this isn't a controlled experiment. However, assuming that
Gareth lives in a marginal area where bees struggle - and I would say rural
west Oxfordshire is not ideal as there are long nectar dearths and a lot of
monocropping - it shows that something about the hive types makes a positive
impact. Gareth is now experimenting with other hive types like the
[einraumbeute](http://www.dheaf.plus.com/framebeekeeping/modified_einraumbeute.htm)
to see how they modify the bees' behaviour, but he keeps returning to heavily
insulated ones, i.e. Warres with extra thick walls or double walls.
Paul
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On 18 March 2018 10:51 AM, Will H <whanrott@xxxxxxxxxxx> wrote:
I've heard Paul say on several occasions that insulation is good for hives
because it ensures a warmer hive. I would like to develop a better
understanding of the advantages and disadvantages of hive insulation. I'm
writing to the group for views. Please pitch in.
So far...
Advantages of warmer hives:
- lower energy requirements over winter limits risk of starvation leaves
colonies in better condition in the spring
- winter brood rearing will provide younger workers who can help the colony
increase in spring
- Varroa mites may preferentially infest brood cells at cooler temperatures,
so higher temperatures may inhibit Varroa reproduction[1]
- fewer cold surfaces may reduce condensation which limits mould and spoilage
by yeasts
- bees are able to move around the hive to access stores during the colder
months
Disadvantages of warmer hives
- warmer brood nest may stimulate winter brood rearing which increases energy
requirements and may leave colonies at greater risk of starvation
- winter brood rearing provides a host for reproduction of Varroa whose
numbers will be greater in spring
- winter brood will be heavily infested by Varroa because there are fewer of
them. This may lead to disabling levels of Deformed Wing Virus. I already see
noticable numbers of crawling bees in spring because of this. These new bees
are wasted effort for the colony
- condensation may be useful for metabolising honey over winter. Bees may
need to fly for water when none is condensing in the hive and risk being lost
You'll see that some of the advantages have -- as I see it -- a corresponding
disadvantage. Furthermore, I wonder whether discussions about warmth may be
conflating better insulation with reduced ventilation. It may be that better
insulation is good but worse ventilation is bad but you can't have both.
All comments are welcome.
Thanks
Will
[1]: From "Biology and control of Varroa Destructor", Rosencrantz et al 2009:
"Depending on the test system Varroa mites prefer temperatures between 26 and
33 °C (Le Conte and Arnold, 1987, 1988; Pätzold and Ritter, 1989; Rosenkranz,
1988), which are significantly lower than the normal temperature in the brood
nest of approximately 34.5–35 °C (Becher and Moritz, 2009; Rosenkranz and
Engels, 1994). Varroa mites are able to discriminate temperature differences
of about 1 °C (Le Conte and Arnold, 1987). It was assumed that Varroa females
preferably invade colder brood cells at the periphery of the brood nest;
however, there is no solid evidence for this hypothesis and the preference
for low temperature may, at least in part, be due to the artificial test
conditions in a laboratory temperature gradient (Dillier et al., 2006)."
