Hi Tom,

Excellent question! The wasps in your photo appears to be European paper wasps. These wasps co-exist with bees. They don't cause any harm to bees. However, European paper wasps are an invasive species. These wasps hunt caterpillars in the garden providing some pest control, but they also hunt caterpillars that we may want in our gardens (e.g. butterflies and moths). 

European paper wasps will only sting if their nest is threatened. When see them foraging on flowers for nectar, or flying around, they generally aren't a threat. If the nest is close to human activity, you could consider removing the nest.

European paper wasps have a one-year life cycle. Once cold temperatures arrive, the nest in your roof will not be able to survive the winter. The only survivors will be new queens which will likely hibernate elsewhere. 

Options:

• Easiest: Leave the wasp nest, once they die out in the fall/winter, seal up the area where they are entering. They will NOT return to the same nest next year. Queens always build a new nest each year. If there is ample room inside your roof, a queen might want to build a new nest if there is an opening (best to seal things up just in case).
• If the wasps are a sting risk, or you would like them gone: European paper wasps make open-faced papery nests, so wasp sprays can be effective if the spray can reach the nest. If you decide to spray, please spray at night, make sure it's not windy, and wear safety equipment (they will sting if their nest is threatened). Follow direction for effectiveness and safety.
• If the wasps are too high of a risk for your comfort, and nest removal will require construction on your roof, I would consider hiring a pest control company for assistance. 

We have hundreds of species of wasps in Colorado! The vast majority of wasps are beneficial in our gardens. They don't cause any harm to bees. Bee and wasps co-exist well. 

The two most common "nuisance" wasps for humans are European paper wasps and Western yellowjackets. Western Yellowjackets are scavengers, and can be aggressive towards humans. They are responsible for 90%+ of ALL insect stings. They also can be a nuisance to beekeepers and honey bee colonies in the fall because food is becoming scarce for the yellowjackets so they try to steal honey from honey bees. A strong honey bee colony will fight off the yellowjackets. Western yellowjackets also only have a one-year lifecycle and can't survive winter. They build their nests in underground cavities. 

More info: 

• European paper wasps: https://extension.colostate.edu/docs/pubs/insect/05611.pdf
• Western yellowjackets: https://webdoc.agsci.colostate.edu/bspm/arthropodsofcolorado/Yellowjackets.pdf

Hope this helps! Please let me know if you have any questions.

Lisa

Lisa Mason
Horticulture Specialist, Entomologist
Colorado State University Extension, Arapahoe County

Lisa,