Before varroan came there could be seen occasional bees with undeveloped/deformed wings in spring. Maybe it was the influence of DWV, Deformed Wing Virus. But it may also have been chilled brood. During the final phase of the pupa development to finished bee the wings are formed. Cold nights and too much of brood could maybe have caused undeveloped wings.
Today, one can probably assume that when you see a wingless bee, it’s DWV responsible. Varroa mites are paving the way for many viruses into pupae and adult bees that had not previously bothered bees. Moreover, these viruses multiply in mites. So today mites spread viruses more efficiently than when the mite had just arrived in Europe. Why that is so is another interesting discussion that probably involves the use of miticides.
The Bee Shaker
The Bee Shaker is a great way to keep track of the level of mites in the bee colony, especially in spring and late summer, so the amount of virus can be kept reasonably low by allowing people to fight the mite if it exceeds a certain degree of infestation. (If that is the strategy chosen.) A good benchmark that many use today is 3%, three mites on one hundred bees (9 mites in 300 bees/1 deciliter of bees).
It also means that to develop a bee stock towards better varroa resistance, you don’t treat against the mite, especially below a mite level of 3%, whenever in the season it is measured.
But if there are wingless bees in the bee colony? It’s usually a sign of DWV and thus too many mites. Here is the Bee Shaker again a good tool, to find out if there really is a high degree of infestation of mites when you see a wingless bee. If you decide to treat against mites if the level is high you might do it to prevent the spread of mites to other colonies nearby.
A colony with a wingless bee
Last year’s breeder queens seem to have produced many queens that have given colonies that control the mites quite well. One of these daughter queens was introduced to a colony that had problems with mites. Perhaps the biggest problem was virus.
This colony was quite weak in this spring and developed slowly, compared to the other colonies in the apiary. I concluded that I would have to check the brood nest to find out the cause. Maybe the colony was shifting their queen?
On a later visit to the apiary about June 20, I saw one, only one, wingless live bee on the hard board in front of the entrance. I then looked in the brood nest, but saw no more wingless bees on the brood frames. But the brood frames had a so called shot gun pattern with a lot of “holes” where you would have expected capped brood as the other cells on the comb contained capped brood. Many pupae seemed to have been removed by the bees. Most likely not due to inbreeding as the queen had mated in the apiary and the number Elgon colonies in the neighborhood was quite high. No trace of any brood disease could be seen so I concluded that a likely cause could be cleaning out of varroa-infested brood. Or could the bees detect virus in the pupae and remove it, without there being a mite in the cell, and remove the pupae?
Could that be the reason why the colony developed so slowly – that the bees were throwing out mites? How had they managed? The wingless bee could indicate that they had not done so well and that the amount of mites was big. Now it was time for a Bee Shaker test to find out the level of Varroa infestation. (Here you can read more about The Bee Shaker, its uses and possibilities: http://www.elgon.es/diary/?p=809)
Here you can see a video clip when doing this test (sorry I’m talking my mother tounge Swedish):
The sample showed zero (0) mites! Then it’s no use to treat, There were far too few mites in the colony. Why had there been a wingless bee recently before the test?
July 8 I was visiting the apiary again. Once again I saw a wingless bee on the hardboard. But now I knew the Varroa level was low. Still no use treating. I looked in the brood nest. The colony was a little stronger still and the brood frames had fewer “holes”. The bees look healthy. They were recovering.
Virus apparently remain in the colony for a while after mites are eradicated – by the beekeeper or the bees.