Solitary Bees

I put up a poster on the  page today to show solitary bee fans five starter projects that I have monitored over the last few years.  I entitled it a ‘Report card’ on the different successes or otherwise. What was great was that I also got three people suggesting they were seriously interested in taking up the hobby for next spring. You can see the report card picture on people who want to raise mason bees.

A fourth person messaged me through the CFSB admin. As I often can more rapidly and easily answer questions by email or PM or in comments sections of my video channel – as opposed to here where I get blogged down in excessive analysis and detail – I thought that it would it would make sense for me to share my response here under a Q&A tag so there could be a searchable record of them. So here goes.

A gent called Trevor asked me the following question:

I was looking to know what size of a hole do the bees need?? I was going to use a few logs and drill the holes into them??

My answer was:

You are in the British Isles, so it will probably be for species such as Osmia rufa (the Red Orchard Mason Bee) which prefer 6 to 8mm diameter holes. Get a very long drill bit so that the holes are at least a minimum of 10cm in depth and make sure the bores are clean and as smooth as possible, equally no burrs or splinters at the entrance to obstruct the entry of the nesting bee. The logs should be east facing and if possible protected as much as possible from rain and excessive wind.

These bees [specifically Osmia rufa] are relatively shy so best not to place the logs where there’s a lot of people walking past. Make sure the people that use the area know that he logs are not for the fire! Stick a little sign up – it’s a good talking point.

I would normally say put mason bee nesting tunnel habitats at least a metre off the ground also as to avoid humidity and an excessive curiosity from ants – mind you, if they are determined the best you can do is displace the logs a couple of metres to one side at night to break the ants path.

I would expect bees nesting mid to late April …and you may not see them initially as they are fast. The first sign is often a blocked hole. You may be lucky enough to also get leaf-cutters you garden area is just right.

Now the last question is when you get them, do you think you would want to have lots more? For example if you want them to pollinate fruit trees such as apple you’ll probably want to say ‘yes’. If that’s the case you’ll have to think about lining the log holes you drill with paper, or even putting out reed tunnels.

The deal is that any population of cavity-nester is often shortly followed or discovered by parasites (flies, mites and beetles). It’s a natural part of the ecology around bees. As you’ll see in the first drill-block in the report card (above), leaving the bees with tunnels that are not disinfected will mean that they’ll become clogged after two seasons and all your efforts will be lost as the bees move on. Or you can – as one person I know does – spend more and more time drilling holes to compensate for those that become unusable. Your decision.

As you can see I prefer that people decide and know how to correctly repopulate their local bees species rather than just abandon a project to getting clogged up.  Disinfecting can be left alone, but you need more holes than you believe and can end up constantly drilling holes in preparations for the next spring.

Unless you have the freedom to spend every spring sunny day on a chair right in front of the blocks (and someone waiting on you), you equally are never really sure whether the nest plug holes you see blocked up are this year’s new nest holes or last years blocked ones – with little bees struggling to get out behind unsuccessful nest chambers; an unsuccessful one in my book, may be a chamber full of mites, pollen loaves with a dead larva or chambers infested with multiple Cacoxenus indagator flies about to emerge and reek havoc with the efforts of the busy nesting female bees.