Keep Predators Away from Mason Bee Tubes

I had a report recently from a mason bee  enthusiast telling me that his mason bee colony had been attacked by rats and most of the cocoons had been taken. These images show what happened. One thing I note in the pictures is that the house wqas on a fence with a platform in front of the bank of tubes. It is best to have nothing that birds or rodents can stand on, and that might have prevented this type of predation.  If one is concerned at this time of year, it would be a good idea to gently fasten a fine mesh wire screen to the opening of the box, or since the activity of the bees is probably finished, moe the house to a cooler safe location — gently because you want to be sure that the bee eggs have been secured into the food matrix.

Identification of Wasp Larvae from Mason Bee tubes

Wings held partly erect.
Wings held partly erect.

In the previous post I indicated I was trying to identify wasps that had taken up residence in mason bee tubes, without actually parasitizing the mason bees



largewasplarvaeI found the larvae in tubes while removing the mason bee cocoons in the winter, and transferred them to a separate jar where I  let them hatch. By May 1 they were hatching so after taking a few pictures, I sent the images off to BugGuide.

The result after several months was an identification by an expert in entomology : Our thanks to  Matthias Buck of  The Invertebrate Zoology Section, Royal Alberta Museum, Edmonton, Alberta, Canada

So he thinks there are actually three species represented in these pictures.

Eumenines prey mainly upon moth larvae, although some take larvae of leaf-feeding beetles.
Adults take nectar.

Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon (Aculeata – Ants, Bees and Stinging Wasps)
Superfamily Vespoidea (Yellowjackets and Hornets, Paper Wasps; Potter, Mason and Pollen Wasps and allies)
Family Vespidae (Yellowjackets and Hornets, Paper Wasps; Potter, Mason and Pollen Wasps)
Subfamily Eumeninae (Potter and Mason Wasps)
Genus Ancistrocerus

There were three species identified from my photographs( labelled above) although it is very difficult to confirm identity without being able to examine a specimen. Next year I will be sure to send him samples to confirm, and I will certainly not destroy these larvae when cleaning out mason bee tubes.

Plants for Pollinators in late May 2016

The mason bees have almost stopped their work of pollination by now.  However several bumblebee species and honey bees were very active around certain plants in the yard this week.

Wasp larvae in mason bee tubes yields newly hatched adults.

2015-12-22wasplarve2When cleaning out the mason bee tubes and recovering cocoons in the winter, I came across several tubes which had been completely colonized by another species of bee/wasp. Images and comments on this can be found in this post:

So now I am trying to get this species identified and will update when I find out. June 6 post shows the identification

Unidentified wasp/bee :Currently under inquiry with the experts.


At first I thought these were the paper wasps as they held their wings outspread but the image below of those wasps from the Polistinae family shows a completely different body pattern. Dr. Matthias Buck of the Royal Edmonton Museum is working on samples of these to do DNA sequencing.


Why Cleaning Mason Bee tubes after November is Important

Today I came across two unopened reed tubes which I had forgotten  in the refrigerator so the cocoons had not hatched out.  The image below shows why it is important to clean your tubes out in the winter and not leave them until late spring.

One cocoon remains on the left at the inside base of the tube. It had a live female which when she hatched would have had to crawl out of the tube through several compartments filled with mites, represented by the orange deposits they leave after consuming  parasitised larval bees.  The mites are in the compartments on the right side, toward the open end of the tube.

If people leave mason bee homes out unattended from year to year, the parasite population expands . They wouldn’t be so successful in the wild where mason bee nests are more dispersed in holes in wood or under tree bark. . When we provide homes for them however, along with increasing the bee population, we are also  multiplying  the success of the parasites. So if we are going to encourage bee populations, it is our responsibility to attend to the cocoons in the fall or winter to be sure they are not contaminated with a new generation of mites.

Mason Bees (Blue Orchard Bees) in action

Some images from this month’s activity of mason bees:

Today I was glad to see them active on my red pear which hasn’t produced well in past years.


A busy Mason Bee Morning

The warm sun encouraged a lot of activity around the Osmia lignaria boxes today .



Put Out Your Mason Bees when Pollinators are Needed

The time to put out your mason bees which have been overwintered in your refrigerator is when you need them to do their work. I release mine in batches.  The first batch was several weeks ago when the peaches and nectarines were in bloom. This week, the pears, plums and cherries are in bloom so I just put out  another batch of cocoons near my bee homes. I will save the last batch for my apple trees which bloom later.

2016-03-31 peachI had to transplant this peach tree this year to the corner of the vegetable preparation building so I found another good spot to place a bee home.

Mason bees always need good mud

Don’t forget to make sure that your mason bees can find a good source of mud while they are laying their eggs in your tubes.  I discovered a year ago that if you provide a reliable source within a few metres of the bee houses, they will use less energy to go to gather mud and will therefore be more efficient.

mason bee crawls into the side tunnel
mason bee crawls into the side tunnel

See this post I did at that time. Another observation has led me to believe that they prefer to collect mud in horizontal holes in the side of a trench.  This trench is kept wet throughout the nest-building period, and I dig holes into the walls of the trench.  It is probably an adaptation to prevent predation, as they would be easy targets on an open patch of wet soil.  They also prefer “clayish ” mud, as any good mason knows that their mud needs to be sticky… Sandy doesn’t do it!

This year I gathered some freshly exposed clay and added it to my mud trench.

Holes drilled in clay for a mud source for mason bees
Holes drilled in clay for a mud source for mason bees


Phragmites reed grass for Mason Bee tubes

Phragmites in estuary/marsh
Last years stems of Phragmites in estuary/marsh being harvested for mason bee tubes. It is important that this is done only before new shoots start to emerge.  I have a theory that this native Phragmites exists in this marsh only because the marsh was fenced in the early years to prevent grazing by cattle and sheep. It has been eliminated from most of the other marshes in BC by grazing (personal communication with Robert Prescott-Allen). The reason this marsh was fenced was that the plant Triglochin maritima  (Sea arrow grass) grows in the marsh and it is toxic to grazers.


“Seaside arrow-grass (Triglochin maritima) is a native plant found sporadically across Canada in saline, brackish, or fresh marshes and shores. This plant contains cyanogenic glycosides, which can release HCN during mastication by animals. Poisoning occurs primarily with ruminants, including cattle and sheep. The concentration of toxic chemicals increases during times of moisture depletion (Majak et al. 1980, Cooper and Johnson 1984, Poulton 1989).”