It was 18°C / 64°F today and the bees in all of my hives — even with shrew-proofing 6mm / quarter-inch mesh covering all the entrances — were out in full force.
I’ve heard arguments that the bees can’t get through quarter-inch mesh. But that’s not true. If it was, my bees would have been locked inside their hives behind the mesh all last winter. The bees in the above photograph wouldn’t be flying around today.
However, I think it’s fair to say that anything smaller than a quarter-inch would be too small for the bees to squeeze through. That’s why it’s important not to just bang the mesh on without paying close attention to how the bees will actually crawl through the mesh. For instance, if the mesh is covering a small entrance, especially a round entrance hole, many of the mesh’s squares (whatever they’re called) will be reduced in size by the rounded edge of the entrance hole. That’s why when I add my mesh, I make sure to line up the mesh so that it’s flush with the edges of the entrance in as many places as possible. The bees can get through the mesh, but they’re most likely to go through the squares on the edges of the entrance, so they can just walk out instead of crawling over the mesh and flopping out a square in the middle of the mesh. If that makes sense. Here’s a photo to illustrate what I’m talking about:
If I hadn’t paid close attention and hadn’t carefully lined up the mesh to be flush with the edge of the entrance hole, the bees would have had less openings that they could fit through. With a smaller entrance hole, say half an inch, every opening in the mesh could be easily blocked if the mesh wasn’t put in place properly. So that’s it. The bees can get through 6mm / quarter inch mesh. But it has to be done right.
See my older post, Quarter-Inch Mesh Doesn’t Always Knock Off Pollen (which contains a video of bees walking through the mesh), for more of my observations on all this.
PART 2: Why I Use 6mm / Quarter-Inch Mesh On My Hives
I use 6mm / quarter-inch mesh to keep shrews out of my hives because in the winter of 2015, I lost six out of my eight colonies to shrew predation — and I will never ever allow anything like that to happen again. It took me five years to build up my beeyard to that point. It took almost two years to build my colonies back up again. It’s been more work than pleasure, and if I don’t soon begin to enjoy beekeeping as much as I used to, I’m out.
So that’s where I’m coming from with my insistence in using 6mm / quarter-inch mesh to keep shrews out of my hives. I know half-inch mesh doesn’t keep shrews out. I’ve caught a few of the shrews and they are tiny little buggers. I had half-inch mesh on my hives during the winter of 2015. It didn’t work. I know some beekeepers who use 3/8-inch mesh to keep shrews out. I also know some beekeepers who use quarter-inch mesh. And because I have no desire ever to take any chances with shrews getting in my hives again, I’ve opted for quarter-inch mesh. Am I a little paranoid? Am I playing it too safe? You’re damn right I am. There is no way I will chance losing 75% of my colonies again. If it happens again, that’s the day I quit beekeeping.
I’m still working out the kinks in my system, but my general approach — in my local climate with Langstroth hives — is to attach the mesh by the first week of October on the bottom entrance, using pushpins, not staples, keeping the top entrance open for a few more weeks when the bees are usually done collecting most of their pollen for the year.
Drones have difficulty getting through the mesh, and sometimes the mesh will knock off pollen from the bees’ legs. Overall, the mesh may slow them down, but they manage to get through it no worse for the wear. If I put mesh on the top and bottom entrance at the same time, yes, some pollen would fall off the bees, but it wouldn’t be the end of the world. And shrews would never get in.
Later in the winter when some dead bees have collected near the bottom board, the pushpins allow me to easily and quietly remove the mesh so I can clean out the dead bees, without disturbing the colony, which I do maybe two or three times over the winter. It’s easier for the bees to pull dead bees through half-inch mesh, but the dead bees can still build up and clog the bottom entrance with half-inch mesh too. For me, there’s little disadvantage to using quarter-inch mesh.
So that’s what I do and why I do it, and so far, it works.