Candling. If lots of light shines through the cocoon, there is no mason bee inside the cocoon.
Four adult parasitic wasps inside this cocoon. Search and destroy, or wasps will destroy your bees.
This candling video shows the technique of candling. Set up a 6V flashlight in a dark room. Place washed and cleaned cocoons in a petri dish. Rotate petri dish over light to more clearly see what is inside cocoons. Remove parasitized cocoons. Go to shop beediverse on this web site to order petri dishes.
Adult bees while hibernating through the winter in their cocoons, are curled up leaving a small area through which light can pass. These cocoons appear mostly black with a bit of light passing through the center of the cocoon.
A cylindrical area in the centre of the cocoon is often an underdeveloped bee that died during development.
