By late September, mason bees have completed their development and are safely ensconced in their cocoons awaiting the return of spring. It’s a good idea to now extract the individual cocoons and store them in a safe and temperature-stable location. This keeps them away from birds and other predators. But more importantly, it helps to limit spread of disease. As you inspect the cocoons, you can cull those that are dead or diseased; and when the bees hatch, they don’t have to burrow their way through the potentially infectious detritus.
Harvesting is very easy. The cocoons are surprisingly tough, despite their delicate appearance. They can withstand some handling, and even brief submersion in water. Last year I cleaned the cocoons by tossing them with sand. Since then I’ve learned that there isn’t any real benefit to this procedure. So after picking out the duds I simply place the viable cocoons in a cardboard box and store them in a cool and dry place.
These plastic trays were well accepted by the bees. Each tube can hold about 8 cocoons. Wasps did manage to get at a few of them, which did not happen in the wood blocks. You can also see a few instance of pollen mite infestation: instead of a cocoon there’s just a mass or orange mite feces.
This cocoon was targeted by the parasitic ‘mono’ wasp. It lays its eggs on the bee larva. In the end, you have a cocoon full of baby wasps.
I’m not sure what happened to this bee. Hopefully it is not a case of chalkbrood. Chalkbrood is a fungal disease that can quickly wipe out an entire colony of bees.
My DIY woodblock houses worked very well. The paper tubes only hold about 4 cocoons. But it’s cheap and easy to make lots of these from wood scraps.