My name is Dr Margriet Dogterom and am the founder and owner of Beediverse. I write this blog for all who love bees and who want to learn more about these wonderful creatures.


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Dave W from Victoria writes.  “I noticed that some mud had been removed from my mason bee box, and when I looked closely in the 3 left holes on the top row they are “padded?” with what looks like a very fine fluffy material and in the middle hole there was what looked like a mason bee with wasp colouration, busily going in and out doing something. I’ve noticed this bee character hanging around on the flowers lately. It definitely has more of a bee-like look, as opposed to wasp-like.

Update from Dave:
The brown stuff at the base of the nest is dried mud which came out of the mason bee holes. I had assumed, since the mud was pulled out around the same time as the bee(s?) appeared and began to put the fuzzy material into the holes, that the new bees had pulled the mud out. But I never saw them pulling the mud out.

Looking on the internet, I am concluding that the invader bee was a Wool Carder Bee since:A) the pictures I found looked like the bee I saw, B) the bee was seen on Lambs Ear plants from which it collects fuzz to put in its holes C) there was fuzz in the holes and D) I observed a specimen defending a flower patch, which is typical for this insect

I guess next year I will watch more closely. Do you know much about these bees? This is the first year I have noticed them around, and I am fairly observant about all the types of bees which are around.

Is now  time to take out the mason bee cocoons and put them in the fridge
beeboxinvaders 001

Cocoon sizes 012010 004Frank M.  writes:  I’m sending this image to you to get an opinion about something that continues to puzzle me. These cocoons are part of my current crop. It’s perfectly clear that the three stacked on the left are females, and the three stacked in the middle are males, but are the three tiny ones stacked at the right end also Mason Bees? I’m finding quite a few of these tiny ones and although they look like Mason bee cocoons, the small size makes me wonder if I’m getting a sub-population of something else.

I will be grateful for your comments. In addition to your views about the very tiny ones, how about the two between the left stack and the middle stack? The one on the left is almost certainly a female, but what about the second one?

Dr Margriet replies:  These all look like Osmia lignaria  I assume that all these cocoons came from nesting tunnels with a diameter of about 7.5mm/ 5/16″.  If so, these are highly likely Osmia lignaria.  There are many smaller species of mason bees  but these are more likely to be found in nests with a diameter of 3-5mm.  The difficulty is with identifying according to size is that cocoon size is on a continuum from small to large
The females range from small to large and the males range from small to large. I am sure the very small   ones are males and the very large are females. The ones in the center are the real question. The only way you can really find out is to see them after emergence. 

I took a high definition photo of some mason bees emerging from their cocoons.  The cocoons that I took out of the tubes were covered in something. I don’t think it is mites. I was wondering if you had any idea.

The bees in the two cocoons on the right are busy chewing their way out in to the open.  You can see the many layers of the cocoons wall.  The cocoon on the left is covered in bee poop! or frass or fecal pellets.    Dr  Margriet


It is early June and I am located in Vancouver.  It looks like we have  a Mason Bee population living under the  flagstones by the house.

Yes these are  ground nesting bees.  Ground nesting bees are solitary bees, and nest up to 2 feet down into the ground, coming out when the soil warms up around June.  Flagstones work great in providing accessible and safe nesting habitat for bee species since flagstones prevents nests from caving in.

IMG_0234 IMG_0231

I found this bee last spring and realized today that she has no wing on one side and what appears to be a deformed one on the other side. So far I haven’t seen others with this problem, but it’s still early.   She crawled under a folding chair and was protected. Have you heard or seen anything like this before?

NoWingBee NoWingBee2Great photos Valer.  I have seen wingless honey bees, but never wingless mason bees.  In honey bees the cause is a Deformed wing virus.  This virus or similar virus could be the cause of what you observed.   Dr Margriet

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