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VIDEO -Predator: Mono Wasp! Learn how to protect your bees

Predatory and parasitic wasps are one of the most common predators of mason and leafcutter bees that can cause catastrophic losses to solitary bee populations. We want to highlight and share an article that is full of incredible photos and information about the different types of wasps that can harm solitary bee populations. With your help, we can help solitary bee populations thrive. Make sure and watch the video below to see what the mono wasp looks like… they’re a lot smaller than your average wasp.




Monodontomerus Wasp, also called the Mono Wasp, use mason bee cocoons to lay their eggs and the Chalybii Wasp prey on leafcutter bees. Both are widespread throughout North America.

Mono wasps seek out nesting holes to lay their babies. Female wasps invade solitary bee nests through small crevices or through incomplete or uncapped cells. They use their slender, stinger-like ovipositor to paralyze the bee larvae by inserting it through the wall of the cocoon. After paralyzing the bee larva, the female wasp lays 20-50 eggs inside the mason bee cocoon. When they hatch they consume the bee and then pupate within the bee cocoon for up to a month. They develop quickly and multiple generations can occur each season, causing a growth explosion, where more Mono wasps can seek out mason bee cocoons. Mason bees are susceptible to Mono wasp attacks up to a day before hatching in the spring.


  • Very carefully remove your nesting blocks at the end of the spring (usually early June) and store in a garage in a cool spot. (Click here to watch video on how to remove nesting block)
  • If you have empty cocoons, dispose of them in your yard waste bin.
  • Harvest cocoons in the fall. Mail your nesting blocks back to Rent Mason Bees in September and we’ll do all the cleaning and maintenance for you. If you host your own mason bees, cleaning is a critical step to caring for solitary bees.
  • Use a flashlight or lightboard to find any see-through cocoons. Those have been compromised, so you can remove them.

THE GOOD NEWS is here at Rent Mason Bees, we’ve noticed a decline of mono wasp predators that harm our mason bees. The main reason is because of our hosts who help care for their bees… thank you!!

Our rental program brings hosts together from around the country to help our solitary bee populations. They take great care of their bees and do their part to help them grow their native bee populations and teach their neighbors, families and friends the importance of pollinators. By not using pesticides, and removing their blocks when we notify them, they help reduce the risk of evasive wasps. Then, in the fall when hosts send their nesting blocks back to Rent Mason Bees, our team goes to work.

We diligently clean EVERY cocoon and hand pick out any compromised cocoons, including wasp invasions. We recognize the “bad” cocoons because when they’re on a light board, they appear hollow as the light shines through.  However, some are so full of mono wasps, they are mistaken for a bee inside. Towards the end of mason bee season, you can open up any cocoons that haven’t emerged and if you find any filled with mono wasps you can dispose of them.

Watch how we clean mason bee cocoons:

Here’s a great video that shows the Mono Wasp lurking around a mason bee block and then getting access to the larva and laying its eggs.

To read full article published by Sustainable Agriculture Research & Education about Wasps. Click here.

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