Bees get a bath

On October 18, nine SPES volunteers and staff came together to clean mason bee cocoons. The orchard mason bee (Osmia lignaria) is a solitary bee native to BC that lays eggs in hollow stems and tunnels of a specific size during the spring, then the larvae develop into adults inside their cocoon during the summer. All sorts of parasites get into their tubes in the bee “condos” that we provide them. Luckily, it is possible to help the bees against those invasions. Here are the steps we follow every fall:


On warm days in early spring, mason bees hatch from their cocoons. Do you see the two hatched mason bees inside two of the condo’s tunnels? You can tell that these are males by the white fuzzy patch on their head, waiting for warmth and females to come out.

The female bees construct little walls of mud between each egg they lay, after providing them with pollen and nectar. The eggs that are laid in the back of the tunnels will develop into females, and the eggs by the tunnel entrance will be males. The next year, males will emerge before the females, so once the females emerge, they can get fertilized right away and start laying eggs.

In the fall, the eggs have now fully developed into adults, inside cocoons. Even with the protection that the cocoon provides, many different types of invaders get to them as you can see in this picture: mold, pollen mites, parasitic wasps, and fly larvae.

To help the bee larvae, we first remove all of the cocoons from the tubes using coffee stirrers.

Still lots of invaders are attached to the cocoons.

We gently stir the cocoons for 4 minutes in lukewarm water with a small concentration of bleach. The bleach will kill the parasites, but does not harm the bees. We do not use soap, as it could be fatal for the bees. We then rinse the cocoons in clean water to remove all traces of bleach.

On paper towel, we disperse the cocoons and dry them out.

Once the cocoons are dry, we store them in the fridge to protect them from predation and parasites, until the warm days of early spring next year. It is important to not keep them at room temperature, as they would emerge as early as December and would not survive for their breeding season in spring.

Come early spring, we will place the cleaned mason bee cocoons in the Native Plant Garden bee condo and in the new Air Bee n Bee condo on the southeast side of Lost Lagoon. We plan to install a few more small condos at the Perennial Garden as well. Come see the bees at work pollinating Oregon grape, red-flowering currant and many more native plants in spring 2019!



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