Why Do Bumble Bees Bump Against Windows?

Bumble bee on Linaria purpurea.Bumble bee on Linaria purpurea.

“I keep seeing large bumble bees bump against windows of our home.  Why do they do that? Will they be hurt?”


Every year I am asked this question!  It frequently happens early in the season, typically when new bumble bee queens have emerged and are looking for a suitable nest site.

Why do bees fly against the window?

A main reason is that generally, some bumble bees are attracted to shade when looking for a place to nest. 

They will seek out crevices and holes that look as though they may provide shelter.  Looking from the outside in, what the bees see is a dark area worth exploring.  Unfortunately, this is when bees will bump against the window.

Does it hurt the bee?  I can’t be sure, but since I have not heard of bees knocking themselves out as a result, and no reports of dead bees by windows, I assume no lasting damage is caused!

“Bumble bees keep getting trapped in my house”

If you have open windows, then chances are you may get one or two bees flying into the house.

My advice is keep calm – they are not out to sting you on purpose!  However, if you are afraid of being stung, by all means wear protective clothing. 

Gently place a cup or glass over the bee, and slide a piece of card beneath the glass, and take the bee outside.

If you are allergic to bee stings, then it would be better to allow some-one else to remove the bee for you!

Bumble bees bumping against windows inside a greenhouse

During the warm weather, if you have the greenhouse door open, you may well get bees flying in, attracted by the plants inside.  This is good news if you need them to pollinate your tomato plants, but what if you want to help them leave the greenhouse?

My method is to leave the greenhouse door open, and have plants by the door, poking into, but ultimately leading out of the greenhouse.   Earlier in the year I had phacelia (irresistible to bees!) and after that, there were mimulus and poppies

You can always position pots of plants to encourage the bees out of the greenhouse if necessary.  It may seem that the flowers would attract bees into the greenhouse in the first place.  However, I tend to find that I can leave the bees to find their own way out when I have plants by the door, whereas previously I felt I had to intervene and help the bees find a way out of the greenhouse whenever I saw bees bumping up against the windows!

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