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I really enjoyed your seminar in Courtney today and went home to open my nest only to find that about half of the cells (40+) had a 1/16″ hole drilled through the paper and cocoon. In reading your book tonight I have not found any mention of this type of predation on Mason bees would you please tell me what would do this and how to prevent it, thanks. Alan A.
Sounds to me that these holes are the right size for parasitic wasps. These wasps parasitize the cocoon contents, and emerge as adults 3 weeks later during the summer. There are 3 ways of keeping these pests down:
1. Candling of cocoons after washing will identify parasitized cocoons and these can then be destroyed.
2. If there are large numbers during spring bee -flight, set out a sticky trap
3. Protect further parasitism after flight by placing bee nests into a wasp free net bag.
“Back when I was cleaning up my cocoons I found three with a tiny hole in them. The hole was about the diameter of a straight pin shaft. Inside each I found 10 to 15 tiny winged insects metallic green in color. All of them were dead. They are about .03 to .04 inches long. Attached (I hope) is a microscope photo of one of them. Also attached is a photo of a cocoon with a cluster of the little guys. Do you have any idea what they are or why they were dead?”Hal
These are tiny parasitic wasps that grow inside a bee cocoon. Looks like there are more than 30 out of one cocoon. Good thing you found it. Candling cocoons can also identify them. These critters can wipe out a mason bee colony. Wasp proof nests are a great way of protecting your bees from parasitism. If was probably too cold when they reached maturity. The last batch of the season did not make it. Dr Margriet
From summer to early winter place mason bee homes inside a net bag. This will prevent your mason bees from being parasitized while they are inside their cocoons over the winter.
Hi Valerie, Thanks for sharing this photo with us and our friends. Yes this tiny little wasp is a parasitic wasp of mason bees (and other insects). You can see from the size of the cocoon in the background how tiny this critter really is! At the moment that this picture was taken, this wasp was listening for bee movement inside the cocoon ( it hears with its antennae). Only live bees are parasitized!! Great picture Valerie.
A comment on this blog asked for more pictures on candling cocoons.
Just today I candled 4000 cocoons. It seems like an awful lot, but when they are in petri dishes it is easy to do candle them- about 30 mins or so. I did see some duds that are of some interest. I call anything that is not a fully developed bee a ‘dud’. The percent ‘duds’ in this batch was 2.5%. Anything under 5% is excellent. But even with 107 duds there are some interesting ones. Few had fully developed parasitic wasps- ready to emerge in spring. Others were bee larvae that had not completed development into an adult. In the next day or so I will take some photos and put them on this blog.
I was teaching a group of people about candling the other day. It is a straight forward procedure but the conditions have to be right. The room that you do the candling in has to be completely dark- a bathroom without a window for example. Any extra light besides the flashlight is too much light and you cannot candle the cocoons.