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PREDATOR – Mono Wasp! Learn how to protect your bees

Predatory and parasitic wasps are one of the most common predators of cavity-nesting 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 your cocoons in the fall, once they’ve fully formed their cocoons.
  • Use a flashlight or lightboard to find and 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 and leafcutter 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 (watch the video below to see how we spot a compromised cocoon). After we clean every cocoon, we safely store them in a temperature controlled environment until next Spring, which studies have shown wasps do not survive well under prolonged artificial cold storage conditions. So… because of our hosts, timing on removing nesting blocks, diligent cleaning of cocoons and cold storage we have seen a decline of mono wasps. If everyone can do their part to care for their solitary bees, we can help them thrive in their environment. So, a big shout out and THANK YOU to everyone who cares for bees!

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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