My investigation into what happened to our strong, 'ready-for-the-winter' hive is still rather circumstantial. I intend to do more research this winter, and to become involved in the beekeeping community on Vancouver Island. There are local monthly meets after the rush of Christmas is over. It disturbs me greatly, but we may need to start chemically treating hives while we adjust to the reality of keeping bees in our new location and to the current threats to their safety. Hopefully I will find some beekeeping hobbyists who can share their experience and advice on the least invasive, least poisonous ways to help our future colonies remain strong and healthy.
The fact remains that there are not enough bodies, and no visible damage to explain what really happened. That is, after all, the confusing situation with honey bees the world over. I tend to lean towards the idea that a combination of stressors is causing the decline in bee populations. Was the move too much for them? Did someone nearby spray chemicals? Was there some form of infection or spore? The only obvious answer to our loss that I could find was the ominous presence of varroa mites in the hive.
As we started out in this hobby, and after significant study, I opted to keep bees in a top bar hive - specifically because it was believed the bees were more likely able to exclude varroa in the building of their own comb, and that the open screen bottom which is part of the hive's design means that mites which fall off of bees will fall completely outside the hive. My intent had been to give my colonies the best chance to live naturally with the least amount of interference necessary. My last hive inspection of the small, remaining colony still in short-term residence showed a significant population of varroa mites - which I had not seen at all in our first year on the Mainland in our thorough (every bar out and examined) once or twice-monthly inspections.
The varroa mite is considered one of the biggest dangers to honey bee populations, and its presence in a hive can result in the transmission of disease. Deformed Wing Virus is one of the major concerns for infection, causing wing and abdomen malformation, pupa death, and lifespans of less than 48 hours for those bees affected. Over the summer, I viewed less than a dozen bees with malformed wings, which may even have been a result of the virus being carried by foraging bees returning to the hive. Now, in the remaining comb, I can see the remains of several bees that never completed their emergence, likely indicating the varroa mite population had outnumbered the brood being laid to the point of killing their hosts.
The winter bottom board - taken off to examine the debris which fell through the bottom screen in the time it took for the bees to disappear. The concentration is below where the brood chamber was located when we prepped the hive for winter.
Up close - the shiny brown ovals are dead mites that have fallen to the bottom of the hive.
You can see the varroa mite latched onto the worker bee in the middle of this picture.
I don't know if the presence of mites in the hive is the cause of our loss, or the result of an otherwise already-weakened colony. The prior owner of the property was a commercial beekeeper for many years, so that may have contributed to a high mite population in the area. When we arrived on the property, I noted populations of several types of bumble bees and wasps, which traditionally are not affected by the varroa (whose lifecycle is unfortunately so well-synchronized with honey bee brood development). Apparently though, varroa are quite happy to hitch a ride on these local insects and can therefore move about the landscape to areas where they can hope to find a foraging honey bee.
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