One Year on: 2013 Mason Bee "harvest" February 19, 2014 17:10

It's late February, and here in Vancouver that means spring blossoms are starting to appear!  If you're planning to set up with mason bees in your garden this year, that means now to a month from now is the time to do it. I had tons of fun with my mason bees last year.  I started with just a dozen cocoons from Blessed Bee Farm (same as the ones we carry) and a house I got from Duncan of (not just chicken coops).  From those dozen I ended up with over 80 cocoons!  This year I'll be starting with about 50 (I had to give some away) and I've seeded some dutch white clover to feed them, so I'm optimistic for a great year! Cleaning your mason bees after each season helps keep their population healthy and parasites in check.  It's also a great learning experience if you've got a microscope!

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The wooden nesting trays before I split them apart

The trays weren't much to look at at first.  With only a few mud caps visible, I expected a disappointing population.

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A tray showing numerous healthy cocoons and several parasitized cells


But there were more cocoons there than I thought!  Among the healthy cocoons I found quite a variety of non-conforming cells.  There was doughy brown stuff, powdery orange stuff, granular orange stuff, and wiry brown stuff accompanied by white maggoty creatures.  A few of the cocoons were small and crinkly, indicating wasp parasitism.

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A close up of another tray. Note the brown wiry material near the centre - if you look closely you'll see several white larvae just below it. This "wiry" frass (bug poop) is characteristic of certain beetle larvae known to invade mason bee nests.

Here's the best photo I got of the larvae.  Kind of interesting, right? Margriet Dogterom of Bee Diverse had some similar photos featured on her blog, so I think maybe these larvae belong to the houdini fly

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These roundish, cohesive balls were the size of cocoons but found in cells that contained neither cocoons nor evident parasites.  They are seemingly comprised of stuck-together pollen. I didn't know what to do with these so I ate them. They were pretty good, short of delicious. See below for what they look like under 400x magnification.

I'm not sure what happened with these.  Under a microscope it looks like partially broken down pollen grains, which reminds me of what I've read about honeybees fermenting pollen with honey to make it more digestible. Perhaps they're provisions for cells that where the bee eggs didn't hatch. They certainly tasted like bee pollen.

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Giving the cocoons a good rinse helps to further rid them of pollen mites

All the cocoons and much of the debris went into a small bowl of water for rinsing.  Some sources recommend a mild bleach solution, but I've just used water here in the hopes of drowning any pollen mites still clinging to the cocoons.

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Healthy cocoons clean, dry, and ready for overwintering in my refrigerator!

 The cocoons can be dried by gently rolling them in a towel.  Not a bad crop for starting with a dozen bees, I'd say!

 400x of a cell overrun with pollen mites
 400x of a cell overrun with pollen mites

The much reviled pollen mite.  This was one of the cells that looked like orange sugar to the naked eye.

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400xA sample from one of the glob like pollen balls (the ones I ate). Note the rounded edges of the pollen granules.  Perhaps this indicates their cell walls being degraded?

More pollen!  This was a smear from one of the pollen balls.

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Wiry frass from larvae that invaded several cells.

A magnified view of the frass.  It still doesn't look like much under the microscope.  I had a video of a larvae moving around too, but I don't think I can upload it.

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The body of a parasitic wasp. I damaged the specimen getting it on the slide. Sorry.

A tiny wasp just a few mm long.  Presumably this was the adult that laid its eggs in some of the cocoons!  I broke it when I was getting it on the microscope.

 400x of a sample from one of the cells containing powdery, light orange pollen.  Note the distinct shape of the pollen grains.
400x of a sample from one of the cells containing powdery, light orange pollen. Note the distinct shape of the pollen grains.


Last slide: this one was from the powdery orange material. Looks like pollen grains with the cell walls all intact. Anybody know the significance of the various pollen appearances?