Is the drowning of larvae another myth?
The following was an article I wrote that was published in a slightly modified form in Issue No 46 of BIBBAs "Bee Improvement" magazine, winter 2015.
I have heard and read many times that when a larva is laying in a cell the breathing spiracles are on the top of the larva, so if you flip it over it will drown in larval food. When writing this short article I thought I would check on the web to see if I could find any further reference to this. I could, plenty, and rather surprisingly in similar wording, including some well respected sources! I don't need to name them, because they are there for all to see.
As with everything else, if the same thing is in several places, especially if from "authoritative" sources, then it must surely be correct, but is it? In over 50 years of beekeeping I have seen enough of the standard and generally accepted information that isn't always correct to now challenge most of what I am told. I encourage others to do the same too. There are many simple experiments that can be carried out by the ordinary beekeeper, without any more equipment than they already have.
It is obvious that many things are simply "cut and pasted", without them being checked by the "writer" who is simply repeating the information.
I admit that for years I believed that larvae that are flipped over will drown. Why not? It sounds perfectly logical and as it's very unlikely to happen: does it matter? In my experience many people who attempt grafting can't see the larvae anyway, so how do they know if they are flipped over or not?
In 2014 I deliberately flipped over a couple of larvae in one cell bar and one resulted in a Q/C, so I thought I would do things with a little more control to see what happened.
During the summer of 2015 at different times over several weeks, I set up a bar of 10 JzBz cups in one of my standard cell bars. My cell bars are numbered 1-10. In each bar I put normally grafted larvae in stations 1-5 and flipped over larvae in 6-10. These were placed in a queenless colony. I did this on 4 occasions, on two I put the frames with 1-5 at the front of the hive, the other two I put them at the back, in case there was a problem with temperature, although in my experience this makes no difference normally. As is now my usual practice I put two larvae in each cell. The reason is because of the low numbers involved and it roughly halves the rejects.
My number of resulting queen cells are in the table below and I think they are quite surprising.
|Normal (out of 5)||4||5||4||4||17||85%|
|Flipped (out of 5)||3||4||4||3||14||70%|
I accept this is not an experiment that can be considered scientific and will never be taken much notice of. Why should it when it has been done by an amateur and conflicts with popular opinion? I have only done the same experiment on four occasions, but I have satisfied myself that yet again we are told things and accept them, when perhaps they are some distance from the truth. I may never be able to repeat the results, but I'm told that scientists often have the same problem too.
I always grafted the "normal" larvae first because I could do them much quicker, but they are consistently slightly better than the "flipped over" ones.
I have very good dexterity but I found it very difficult to turn the larvae over. You would have to be incredibly clumsy to do so, making me wonder why this whole business is considered worthy of mention so often in the first place.
I didn't witness it, but I have been told by someone who attended a presentation by a well known beekeeper that they never do grafting, because they accidentally flip the larvae over and they drown! As I have found it very difficult to do, that sounds more like a pretty good excuse for not being able to graft to me!
I suspect I damaged some larvae in turning them over, which may be part of the reason the success was lower, but even then, 70% is quite acceptable.
I don't expect this to become a big issue, but all I will repeat is that if you are told something, even though it is widespread, then challenge it and do a few checks yourself. There may be some who try a similar experiment to this and have total failure, so they will disagree with me. That doesn't matter, they are doing it from a position of experience, not just accepting what I or anyone else writes or tells them.