Friday, 21 April 2017

What's the diagnosis?

A strange thing happened yesterday when I was weeding in the garden.  Something fell on my head and bounced down in front of me.  I could see at once that it was a bee and was small, pale and obviously unwell but it was only when I picked it up for a closer look that I realised it was a honey bee.  Apart from being lethargic and unsteady, and making no attempt to fly, the most striking thing was its stunted abdomen.  Normally a honey bee's wings don't reach the end of the abdomen so this one obviously had a problem.

I put it on my glove to keep track of it while I went to fetch a camera.  It was falling around and was unable to right itself if it fell over.

I didn't notice at the time but the other striking abnormality on the photos is that the metatarsus on each hind leg is transparent, so that you can see the pollen brush on the inner side from the outside.

Then I noticed another honey bee crawling on the lawn.  This one looked physically normal but was also making no attempt to fly.

Here are the two of them to show the stunted abdomen in the first bee.

Another thing I noticed was that on both sides it had a K wing deformity - where the fore and hind wings are disconnected and held in an abnormal position.

The first bee was unaware of what was going on but the second one seemed to sense that the first had a problem.

So we have a small sick bee with a stunted abdomen, bilateral K wing deformity and transparent metatarsus and tarsus on its hind legs.  I had earlier been watching the hives and all seemed normal.  Today I have inspected all four hives and everything seems fine.  I did 7 day varroa counts last week and they were the lowest I have ever had, after Bayvarol treatment last autumn.

So what is the explanation?  I have read that K wing is a sign of acarine (tracheal mite) infestation but none of the other bees seems sick.  Deformed wing virus can produce a stunted abdomen but this bee doesn't have deformed wings.  And what about the transparent metatarsi?  One other puzzle is that this bee was clearly incapable of flying and yet it had fallen out of the sky and landed on my head.  The hives are on the other side of the house about 40m away.  And what are the odds of it falling on my head?

I don't know what the answer is.  If the bee went to see her GP (family doctor) she'd be told "it's probably a virus".  If you have any ideas or suggestions please do leave a comment.


  1. The 1st one looks to be very young (paler& v fuzzy)....
    I was in NE46 today planting my Dads was not warm , especially with the way that breeze got up midday.
    Chill could be a factor ?
    Def K wing
    Have not heard any reports of accarine in UK Perhaps NBU, or RBI (Ian Wallace i think) could check it for accarine?

    1. It is pale and fuzzy but, in theory at least it, should be at least three weeks old to be out flying. The stunted abdomen and the transparent legs must mean this is an intrinsic abnormality of some kind.

  2. Chris,

    Just my two cents here, but not all bees with deformed-wing virus have deformed wings. The manifestations of the disease correlate with when, during the development of the pupa, the bee contracted the disease. If the wings were already formed, they would not be affected. However, other body parts could show symptoms. Overall vitality would be affected as well.

    You are absolutely correct that stunted abdomens are associated with deformed-wing virus. I don’t know about the leg translucency, but that is interesting and something I will look up.

    Remember, too, that when you kill the Varroa mites, you are not harming the viruses that are living within the stricken bees. We know that there is some lateral transmission of deformed-wing virus from bee to bee, so even after the mites are killed, the virus can spread. It is not nearly so quick or efficient, but the possibility still exists. There is also some vertical transmission from queen to egg, assuming the queen is infected.

    As for the bee landing on your head, my assumption is that the bee was carried out of the hive by an undertaker bee that was removing the dead and near-dead from the hive. It’s a common occurrence and I’ve watched it many times. At my place, they leave the top-bar hive and fly over the concrete drive, where they drop the doomed.

    Don’t know about the second bee. She looks older, but her wings are not frayed. So no clue.

    Thanks for giving us something interesting to think about. I look forward to your posts.

    1. Many thanks for your comments Rusty. The undertaker bee is a great suggestion. I had thought about a bird dropping it but it would then have been at least crushed. It is pale and fluffy so I guess it was spotted as defective straightaway after emerging and was removed. Still the undertaker was a pretty good shot.

      I couldn't find any reference to K wing being caused by DWV but could find that it is associated with other viruses. I wonder if this bee might have had more than one virus? The legs are a puzzle and I couldn't find anything similar. If I had noticed at the time I would have taken a few closer photos. I did wonder if the other bee was just at end of life having been an over-wintering worker but as you say she isn't very worn to look at.

      Two cents is interesting. We say two penn'orth (pennies worth) which I guess is about the same.

      Thanks for your ideas and interest.

  3. Would seem to be the traits of varroa destructor, (wing and abdominal deformaties) and probable cause of landing on your head was that it had been expelled from the hive by another bee! An isolated case in one of your own colonies? or maybe even a feral colony nearby?

    1. I think you are right about it being dropped by another bee (see other comments above). There are also bees in a chimney about 100m away so it may have come from there. Thanks for your interest.