Kinds of Mason Bees/ effects of management

I live in Denver, Colorado, and am organizing a project where children will build Mason bee homes, and then report on residents. I have a quick question.

The instructions I have say to make the holes, tubes, whatever about 5/16th inch wide. I know there are lots of types of Mason bees, including quite a few here in Colorado, both introduced and native. I know that Leaf cutter bees live here, and also use the mason bee houses.

So, what kinds of mason bees and other bees will use holes of this size? I would like to be able to print out pictures of likely visitors for the children.

Also, what longterm effect will it have on bee populations if we (people in general) remove tubes, and sort and store them over the winter?

Maybe this will help:

http://en.wikipedia.org/wiki/Mason_bee

and

http://www.buzzaboutbees.net/types-of-bees.html

Thanks for the links.

Also, if I made some different sizes of holes, would I get lots of different bees? Could I manage them the same way I would manage mason bees?

I would imagine you could manage them the same. The main issue would be the smaller the bee the harder to manage. Tube size would be tougher in the smaller sizes as well.

As far as different sized holes, you could do that in the same housing but my inclination would be to do them in different houses to keep them separate.

I read through the Wikipedia article and found part of it confusing. It says that mason bees like to nest in tubes, but that drilled holes aren't preferable because it makes harvesting them difficult and it makes it difficult to manage pests. If I've got a block of wood with 5/16" holes drilled 3-4" deep. Will this work without having having to find a way to harvest them, and let them come out on their own, as long as I were to plan on cleaning out the holes annually? Just trying to think of a quick, easy project for kids to do as well.

4" will work, but 6" is better

just make your own paper tubes from parchment paper. roll it around a pencil and slide it into the drilled hole, check out one of the many youtube videos on how to do this,

Patrick Mann wrote:just make your own paper tubes from parchment paper. roll it around a pencil and slide it into the drilled hole, check out one of the many youtube videos on how to do this,

Roger on the 4-6" holes. The paper tubes are just for making them easier to clean or in case you want to harvest the larvae, correct? Otherwise you can just drill the 5/16" hole and either toss it and start over every year after they've emerged, or ream it back out?

You can do as suggested each year to be on the safe side. You can use the drilled block for more than one year. I would not use it more than 3 years though. I would certainly use the 6" depth as well.

Holes in wooden blocks (without liners) are not a great idea because if you just leave them out for several years, what you are doing is building up a hotel for bee parasites, which can actually reduce the number of bees in your yard.

Here is what happens:
1. You put out wood block with holes
2. In the early spring, the bees find your block and lay eggs in it, along with a few parasites
3. The following spring, the bees hatch, and lay eggs in the block again. The parasites are still in the holes, and the bees also bring in a few more parasites.
4. The parasites have a heyday.
5. Go to step 3

Over time you will have tons of parasites and not so many bees.

If you throw out your block, you will almost certainly be throwing out unhatched bees. In my nests I have never seen a time when all the bees are out of the nests (I use tubes). If you wait until all bees have hatched, some bees will have already laid eggs. But I suppose that may kill the least number of bees if you throw out your block at that time(?).

A better approach is to put the whole block inside of a cardboard box or paper bag which has a few 1/2" holes cut near the bottom (see http://www.crownbees.com/how-do-i-transfer-from-old-blocks-or-straws-to-new-straws/ ). The bees will hatch out of the block, land on the floor of the box/bag, and find their way to the holes. They won't go back into the hole in the box/bag. You should have other tubes/blocks available for them to use. Once they all hatch, you could take the block out of the box/bag and clean out the block. So if you had two blocks, you could rotate them like this. But like I said, I would use tubes instead of blocks.

I use bundles of teasel stems for my bees, which is working great for me. Any hollow plant stem will work as long as the hole is about 5/16", but I include stems all the way from 1/4" to 1/2", and the bees use all of them. I have had some other bee species use the smaller stems (not sure what species). I think stems would be great for kids because all they have to do is assemble the bundles (vs. drilling holes). If they are old enough they could cut the stems too. And if they are really old they could go out and collect the stems from the field. Many plants with stems are invasive, so most landowners would love for people to come cut them down. I cut mine right before they go to seed. Bamboo stems also work well, but around here teasel is the easiest to find.

If you want to make tube bundles, I recommend holding them together with bulk 1/8" bungee cord, something like http://www.amazon.com/Paracord-Planet-Shock-Various-Colors/dp/B00HAMI6R0 . I used to use rubber bands, but even the biggest ones would not last through the summer. The bungee lasts a long time. I have been using regular bungee cord to hold bird houses, and some of it is 12 years old.

If the bundles are going to be exposed to the weather, you should make some kind of roof for them (two pieces of cedar fence board or something like that). You can also make or buy boxes to hold the tubes. I have used plant pots for this purpose. They are OK, but I think I am going to switch to just bungee cord. I have problems with the tubes falling out of the pots on windy days.

I recommend that you open your tubes and clean the cocoons. http://www.crownbees.com/category/what-to-do/harvesting-cocoons-in-the-fall/ has good info on that. That is a great activity for the kids to help with, because they can see what is going on inside the tubes. To open a plant stem, hammer a chisel through the joint in the stem and twist the chisel. This will split the stem along most or all of its length. Bamboo tends to split all of its length, teasel usually doesn't split quite the entire length, but you can just pull it apart with your hands. I can provide more details on how I clean them if you'd like.

Back to your original question about the longterm impact - as long as you leave about 60 bees per acre, you should not be negatively impacting your native bee population in the long term. And of course the bees will be nesting in other places than the housing you provide (otherwise you would not have any native bees). If you re-release all your bees, their population will grow, up to the carrying capacity of your property, which depends on how much pollen is available to the bees, nesting sites, predators, weather, etc.