31 March 2016

Winter bees and Summer bees

There's a neat evolutionary trick or two that enables colonies of honey bees to overwinter, and it isn't just the bees ability to cluster for days (weeks) on end when it's cold. Clustering, don't forget, is essentially an emergency measure to protect the queen and to keep her warm and safe.

Bees cluster when they collect around the queen whilst they're searching for a new place to live after swarming from the parent colony, and they will cluster when the inside of their nest is too cold for them to be able to safely walk around on their own without freezing to death. It's a pretty dangerous thing to do though, because a clustered winter colony will always settle over brood – the future of the colony - and can starve to death a mere inch or so away from food, which is why choosing the right nesting site after swarming is pretty important,
and why modern beekeepers try hard to keep their colonies warm by adding a layer of top insulation above a closed crown board because that bit of extra warmth can reduce the frequency and length a colony may need to cluster and also reduce the amount of stores needed.

The 'normal' lifespan of an Apis mellifera worker bee is a mere 6 weeks – it's 3 weeks from egg to bee; 3 weeks growing up and working inside the hive; 3 weeks flying and foraging – but a winter worker bee may have to survive for as long as six months in some parts of the world because they have evolved and adapted to live in a climate where it's too cold to fly, and where native plants provide little or no forage, during the coldest months of the year.

The main job of winter bees is to keep the colony merely ticking over, and to make sure the queen survives the winter dearth. In nature they are almost totally reliant on their previous summer's sisters for both the location of their nest and their food supply, but they will zealously collect the last forage crop of the year (Ivy) and top up stores on a good day.

Some beekeepers don't seem to realise, or have forgotten, that the 'Winter' bees that were raised in the latter part of the previous year – from August onwards – have a different anatomy and physiology to 'Summer' bees. There are two main differences.

Winter bees have 'fat bodies' (areas of fat) within their abdomen, mostly insulation to help them keep warm. Winter bees have a longer gut than their summer sisters, to store a larger volume of faecal matter, which in turn means they need to defaecate less often. This helps a lot when they are confined to the brood nest due to bad/cold weather, and explains the surprisingly long curls of yellow on newly polished cars after a sunny wintry day's cleansing flight.

These winter bees don't have active wax glands because they don't need them. A wintering colony wouldn't normally need to draw comb because it will take up less comb space than the higher population of the previous August. These long-lived bees are actually likely to spend time drilling tunnels through comb to make communication quicker and easier, and so probably chew and destroy more comb than they'll ever produce.

Winter bees don't need to cap stores with wax, because there's next to nothing coming into the hive during their lifetime, and by Spring a colony will have emptied enough stores to ensure there is plenty of space for the queen to lay. We beekeepers, especially new beekeepers who seem to think they should feed all year round, can mess all this up by overfeeding – making the winter colony work hard to store and cap food, and using space for stores which should be left vacant for the queen to lay in the Spring.

Winter bees won't ever need to raise large amounts of brood in one go, because the queen's laying rate reduces during autumn and only slowly increases again after the winter solstice, but colonies always need a supply of young bees because these are the ones that feed the developing larvae which is why in most parts of the British Isles there is almost always a small area of developing brood to keep warm.

As egg laying increases after the shortest day so does the population of young 'Summer' bees, which in turn enables the queen to lay more eggs because there are more and more young bees to provide food for the larvae. But, and it's an important but, the lowest point for the colony's population is usually towards the end of March or later – not January or February – because in March the remaining winter bees are dying and there are not usually yet enough summer bees to fully replace them.

March and April are also the critical months for stores, because the low numbers of active foragers may not be able to replace the food being used to raise brood and feed the 'house bees', but it can all change in a mere three weeks. It's this time that the beekeeper needs to be particularly vigilant, and perhaps add some fondant.

These two things winter bees don't usually do – wax making and feeding developing brood – are more normally the preserve of young 'house' bees, and more especially young 'summer' house bees. This is why a natural swarm will always take a range of bees aged from about day 6 onwards (when a young bee is able to fly). It is, though, why there is almost always brood in a colony, except in the days either side of the shortest day – because a successful colony will always need young worker bees.

Young workers aged between 4 and 12 days have active hypopharyngeal glands which enable them to make royal jelly and 'brood food' from pollen, this gland atrophies around day 12. Wax making for comb building and store capping is done by workers between 6 and 12 days old – after which the wax glands atrophy.

These two types of glands can be reactivated in an emergency, but nothing a careful beekeeper does should cause the colony to react in this way – we shouldn't cause an emergency – and that's why timing of any 'Spring procedure' the beekeeper wants to carry out can be fairly critical to a colony's long term future. We shouldn't force foragers to revert to house bees, and nor should we force house bees to skip a stage in their in-house development in order to become foragers – both things can shorten their lives.

Bees don't organise themselves according to the Gregorian calendar, they have evolved to be in tune with their surroundings and the vagaries of their local climate, and we beekeepers need to do our best to read these things too. We shouldn't ever shouldn't try to force our bees to do something they aren't ready to do just because it suits us, or because we did it on 'that day' last year.

There has to be a very good reason to inspect a colony in February, March and early April. Opening a hive so as to put a note on facebook, a video on youtube, or a comment on an internet forum isn't a good enough reason.

So, all in all, the beekeeper needs to sit on their hands for as long as possible in the Spring, and to wait patiently until the bees tell them they're ready to be worked on.


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