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Dead bees in air conditioner #876860

Asked July 11, 2024, 4:12 PM EDT

I recently had my air conditioner cleaned for the summer. When the worker took off the outer part/cover of the unit, he found many dead bees. He did not find a nest or hive and no live bees were there, only dead ones. A few years back when the same company did the summer cleaning of the same air conditioner unit, the same type of photo was taken with hundreds of dead bees, with no nest or hive. The worker had indicated that he had never encountered anything like that before in all his work. He suggested I contact the company that I have that does pest control. When they saw the photo, they, too, had never encountered anything similar to that. None of my neighbors have had this happen to their air conditioners. I'm hoping to learn why this is happening and what I can do to avoid this in the future. Photo attached.

Dakota County Minnesota

Expert Response

Hi Susan,

These appear to be wasps. If you search the web there are quite a few videos and posts about wasps that build nests in AC units, and some that show piles of dead insects inside like yours once they've died.

My best guess is that there's an old nest under or somewhere in this unit. Wasps -- these may be yellow jackets, but I'm not sure -- use their nest for one season and then die.

Yellow jackets are good at hiding their nests. I don't know that there's any way to prevent them from building inside the unit again, because the vents can't be closed. My recommendation is to ask your AC company if their presence could damage the unit in any way. If not, you may want to live with it. It may never happen again; yellow jackets don't reuse their nests. 

Here's more information:

https://extension.umn.edu/yard-and-garden-insects/wasps-and-bees

If you are determined to make sure they're not rebuilding this year, consult with your pest control company.

I hope this is helpful. Good luck.


MJ Replied July 11, 2024, 10:23 PM EDT

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