Why Do They Keep Building It?
I had to remove burr combs for the first time this year. I felt so guilty for doing it since there were so many capped cells and open cells with larvae and eggs in them. I have wasted a few hundred would-be worker bees.
Two weeks have passed since I first spotted the burr comb, by looking up from under the hive, but I couldn’t do anything about it. It had been either too windy or raining, and on the one good weather day I was at work. The next thing I knew the burr comb almost reached the screen on the bottom board. I opened the hive for inspection and lifted up one of the foundation racks, the comb broke off. Not much I could do, really.
Aside from partially filled cells on the foundation, the bees have built the burr comb right under four of the foundation racks. It was as though they used the bottom of each foundation as the anchor bar for building a comb in the same way as a top bar hive. They were perfectly shaped combs. I know that bees will try to fill up any space between the foundations if they aren’t spaced perfectly evenly. But under the foundations? I thought perhaps because I used a deeper hive body, but the hives are identical and it’s the only hive that’s doing it. The other hives are behaving normally. Maybe these bees were traumatized? This group of bees did have an unhappy and unusual, albeit short, experience I will alliterate in another post.
Ten days after I did the last inspection, the bees started to build the burr comb under the foundation again. Hopefully the weather permits me to open the hive and scrape it off before the queen lays eggs in them. I’m still trying to figure out why this hive keeps building burr combs. I’ve changed the hive body from deep to a medium one as an experiment and it seems to be working so far. They’ve stopped building the burr comb but they are bearding outside in the morning and afternoon whenever it’s hot and humid. I hope they’re not planning to swarm so soon.
Petals and Wings 
There must be a huge amount of space under the bottom frames? My hive doesn’t give the bees enough space to do that. Do they have space to expand elsewhere in the hive?
If you still have the comb it would be a good idea to open up the cells with an uncapping fork or other implement and check for varroa mites.
Yes, there was too much space. I’ve already switched from the deep super to medium super, and they have stopped building the burr comb. They’ve been bearding instead even after I put the shim in to help the air flow.
If we understand the situation you are using medium frames in a deep body. Is that correct?
If so it sounds as if the bees are responding normally if inconveniently. When we obtained a medium-framed nuc to put in our deep-dimensioned horizontal hive, the seller predicted that the bees would simply build comb past the bottom bar of the frame to within bee space of the floor.
In our case that did not happen but that colony failed to thrive for us at all.
You are correct. I just wanted to try a deeper hive body to give them more space. I thought that they would just build burr combs between foundations, not under them. I did change the box to a medium size and they have stopped stop doing it. I think this one hive is the problem since the other hive that I’m using also has medium frames in a deep body and the bees haven’t indulged in burr comb under the frames and seem to be doing fine.
But is the trouble-making hive doing better? Our nuc-originated hive also did fine as far as maintaining numbers but they did not grow and were later wiped out by wasps and robbers. We have heard it said that too much empty volume to fill can intimidate some colonies.
So far, there are plenty of bees bearding in front of that hive. Will know better after the next inspection.