Lovely warm day today for a thorough inspection. Fortunately I have a strong colony with no sign of disease. But I’m still very new at this and have some questions. My hive overwintered with two full-depth brood boxes, and on removing the upper frames I found that there is burr comb between the boxes, and as the top frames came out the burr comb was pulled apart revealing big white grubs. Presumably these will now die. Is this normal and/or is there anything that can be done to prevent it?
Welcome to the site.
This is usually caused by the bee space being incorrect between the bottom of the frames in the top box, and the top bars of the frames below.
You are correct that these damaged cells will now die, and it’s a less than pleasant job to clean up. If you have the top box off, I would use the hive tool to scrape the top of the bars in the bottom box to clean them up. Alternatively you can leave them and the bees will correct/clean it up, but may continue to use this space for brood.
Based on this, I suspect the queen has moved up in to the top box, did you find many brood filled frames?
Same thing has happened to me. Not a good feeling, seeing those exposed larvae/pupae. It’s my first inspection with a colony I established around Christmas time. My hive is all Manley depth boxes, which measure 169 deep. The frames are Guilframes, which measure 150 deep. That’s 19mm between frames: around 11mm too much, from the reading Ive done. Time to fire up the table saw and take a slice off the boxes I think!
19mm is crazy!, it also doesn’t account for the 2-3mm above the top bar in the lower box.
You will generally find this specific spacing issue is caused by one of three things:
Metrication of imperial hive dimensions
Essentially the conversion from imperial -> metric causes these kinds of issues. In some cases, it’s not the single conversion, but it appears that manufacturers convert back and forth and from each other over time… and the numbers get more abstract as time goes on!
Although there are ‘standards’ in the Langstroth hive, they have a large amount of variance, especially when working outside of the standard full depth boxes/frames. I have found when dealing with Ideals that they vary from manufacturer to manufacturer, and combining the wrong box with frame has led to what you describe.
Top / bottom bee space
This one is a little more obscure (and very specific), but can lead to the exact problem. Hive boxes / woodware will be manufactured with either top or bottom bee space, that is, whether the bee space provision is above or below the frames, based on how they hang in the box/super. If you have a manufacturer with bottom bee space, on top of a box with top bee space, the gap will be much greater than it should be. This explanation isn’t perfect either, because how much manufacturers ‘give’ to the top/bottom space can vary too. This really comes back to mixed manufacturers, but is worth knowing too. Many sellers wouldn’t know if the equipment they sell has top/bottom bee space, it’s always best to measure yourself! Good page on UK hive top/bottom bee space here: http://www.dave-cushman.net/bee/torb.html
Thanks for that detailed response. It explains a lot. So perhaps now you can talk me through the dimensions of a base board…it seems to me that the average base board has a 10-12 mm ‘wall’ height, upon which sits the bottom box. Does this not create extra space below the frames for burr comb?
So the wall height you refer to is interesting. I have never had issues with bees building down to the bottom board… this may be luck or it may be for other reasons (if someone has details on why this is let me know). I suspect it is to do with the fact the bees know it is the bottom of the hive and level with the entrance (although if you ran exclusively top entrances what would happen? )
I have run higher edged bottom boards without issue, ie. this drawing shows a 20mm measurement, which is then added to the space at the bottom of the box.
At some point in history this style of bottom board took over. If you look at the original designs for Dadant’s hive it shows a far more uniform space between brood/super frames, and brood/bottom board. Even more interestingly, there is no edge on the bottom board and the additional spacing is incorporated into the brood box.
As the brood box in the Dadant hive always remained at the bottom, this was possible. With the move to ‘modern’ Langstroth, the portability/uniformity of the boxes appears to have survided, so the base board now has the spacing incorporated.