Hive post-mortem

It is always really important to conduct a post-mortem on any hive losses, as it’s a vital part of our learning curve with beekeeping. Sadly in many circles, losing hive is regarded as a “failure” which, if you are observing and watching and monitoring your bees rather than working towards a homogenised collection of colonies, it is not. Only by evaluating what is going on can we determine the actual world our bees are working in, and if we keep overriding the system then we lose valuable data on how bees actually behave and function in our own apiary. This is always tricky when it is your first/only hive, as is the case in this instance with one of my former students.

This colony was a swarm that had been collected in mid-July, but was of unknown provenance. I always recommend collecting swarms as they are a great way to start out, but it is a good idea to know whereabouts they came from. This is not always possible of course, but if you don’t know if they’re a prime or a cast, how long since they issued, or whether they are from managed hives or a feral colony, you do have to keep an open mind on how well you can expect the colony to do.

July is quite late for a swarm, in that they have a lot of work to do in building up their colony as well as gathering enough stores for the winter. It was a reasonable size, but we weren’t sure if it was a large cast or a small prime. They had 4 frames of drawn foundation donated by the swarm collector, and some built comb from a previous colony which had absconded.

They started well enough and the queen was laying in a beautiful pattern:

Perfect. However, despite this, they weren’t really building up, and were still only covering about 4 frames. Late swarms really need to crack on if they are going to gain enough stores and a large enough volume of bees to insulate and look after the nest in order to make it over winter. It wasn’t looking terribly promising by the time we got to the end of September.

Now, here is the difficult decision. As beekeepers, we have a number of things we can do in order to support our colonies and help them to survive in spite of other factors such as poor weather or a substandard queen. However, you have to weigh up the value in doing this. A healthy colony – even from a late swarm – should build up, or at least progress in such a way that shows intention and an ability to thrive. This is where simply observing numerous colonies in their natural state comes in to play. It’s not just years of beekeeping, it’s exposure to a diverse range of bee colonies so that you can gather a body of knowledge about bee behaviour in general. Having witnessed swarms who have a strong sense of purpose, it’s quite noticeable when a colony is lacking “oomph”, or just doesn’t seem to be a good do-er, to use a livestock term. You need to think whether the bees themselves, your apiary, and the other bee species are going to benefit from you helping out a weak colony.

I thought the colony unlikely to make it through winter given its lacklustre nature so far, so we left it to its own devices. On checking the inspection board there seemed to be a large amount of Varroa, so we checked regularly to see what was going on in the hive. One week there was an absolute carpet of mites. There were also bee antennae, and we wondered if the bees were pulling out infected larvae, ie demonstrating hygienic behaviour. However, they were still only covering about 3 frames, and that infestation in such a small colony meant it was a huge burden for them. However, they were still flying so we just kept an eye on the Varroa.

On looking at them this weekend, the colony had died.

There were a few bees on the frames, and they were completely out of honey, but there was no brood, or indeed evidence of recent brood. No sign of any other disease, and the combs smelled normal. No funny deposits or mouldy brood. There was an awful lot of Varroa on the floor and inspection board, and on taking a closer look, on the bees themselves. We have had a night or two of frost, so a combination of cold and starvation will have finished them off, but the main issue was the mite load. We found the queen, and some bees, and got out the torch and hand lens.

You can really clearly see the mite lodged between the plates on the abdomen. This is the favoured refuge for the mite to anchor itself as it can evade detection, this area being a grooming ‘blind spot’.

Here is the queen:

In the third picture, it’s apparent that she’s quite a small specimen but this might just be because she’s not laying, so her abdomen is not swollen with eggs. However, you can see that she’s a completely different shape to her [worker] daughter below.

So, the obvious questions might be: why didn’t you feed them? And why didn’t you treat them?

As I mentioned at the start, it’s very easy to jump in and help because we can, but in these days of scarce resources and the numerous challenges that face our bees, it’s not worth propping up a weak colony. Yes, they could have been fed, but that wouldn’t have helped the mite issue. Yes, we could have treated them but was it really worth it, given they were already struggling and very small? Maybe they absconded their original hive because of the infestation. Maybe they were suffering some other malaise and the mites took advantage of their reduced ability to cope.

This has prompted me to have a look at the biology of the mite, and the relationship with its host, the honey bee.

This study shows how the mites sit on flowers and wait for a passing bee, where it then hitches a ride back to the colony. As a single mite can start an infestation, even if you treat your bees, it will not stop mites reinfesting as they will get back on to the bees. As also pointed out, grooming behaviour by the bees, and chemical “masks” created by the mite can help or hinder the rate of infestation. In other words, bees need helpful genetics and behaviours to aid them in their fight against Varroa. Dousing them with mite treatments of course gets rid of a lot of adult mites, but it is not solving the problem. When favouring certain colonies to keep or use to make increase, the standard practice is to choose those which are good honey producers, or with a calm temperament rather than resilient bees who can undergo their own mite control.

Feral colonies have mites, but they seem to deal with them. Maybe this is because the only remaining feral colonies are those who have adapted to a mite load, by grooming or by other hygienic behaviour. Perhaps it’s to do with the cavity they live in being much more insulated, or having a diverse biota living with them, and the fact they are never opened up. Managed colonies tend to be more concentrated in an area which can increase the burden and likely cross-contamination, as put forward by this article. Swapping frames and bees between hives and mixing colonies is presumably an easy way for the mite to spread.

As with everything, an understanding of the elements we are dealing with in the equation is essential. Going treatment-free is a way to weed out those colonies that cannot cope, or where Varroa has taken a hold. Although it is true that bees becoming immune to Varroa will not happen quickly, nor will evolutionary pressure exert much influence all the time beekeepers can interfere, there are valuable lessons to be learnt as we watch how our bees deal with their foes, given the opportunity, as the tools are there – as evidenced by the large number of long-standing and viable feral colonies that pepper our countryside and buildings; there is still so much we don’t know.

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