New Variety of Wasp Moves into Colorado, Changing Ecosystem and Increasing Potential for Stings Around the Home

Colorado will be plagued by a new springtime pest this year that has been inadvertently imported from Europe. The European paper wasp is fully anchored in Colorado’s urban settings, posing new nuisances and perhaps altering Colorado’s garden ecosystems forever.

European paper wasps began moving across the state over the last three years; this spring, experts expect to find them in almost all areas of the state, according to Whitney Cranshaw, Colorado State University Cooperative Extension entomologist.

"Because their nesting and eating habits are different from the western yellowjacket, the common wasp in Colorado, people will need to be aware of the differences between the two varieties to protect themselves from stings and to control problem wasps," said Cranshaw.

Unlike the western yellowjacket wasp, the European paper wasp nests in small cavities, such as poles, under eaves and children’s playground equipment. Because they nest around the yard and in small, obscure areas – even something as small as a bolt hole can be an entrance to a nest – the incidence of stings associated with this group of wasps can be high.  

Western yellowjacket wasps scavenge for food, feeding on dead insects, garbage, meats and sweet foods. However, European paper wasps feed on live insects and live primarily in urban settings, supported by insects that live in gardens such as caterpillars, hornworms and cabbage worms. While this predator can be beneficial in controlling bug populations, the wasps can also make a drastic impact in other insect populations.

"These wasps are eating many insects," said Cranshaw. "In one aspect, this is beneficial because they feed on hornworms or cabbage worms, insects commonly thought of as pests. But they’re also very hard on some of the caterpillars that turn into interesting butterflies. I think the wasps will have a major ecological impact on garden communities in the state."

These wasps look remarkably like a western yellowjacket; it is shiny black and yellow. The European paper wasp is somewhat thinner and longer than a yellow jacket, and its legs are longer, usually noticeable as they hang from their body as they fly. These wasps also are less aggressive than the western yellowjacket, but sting when they are disturbed. European paper wasp make paper, open-cell nests that are not covered by a papery envelop or mud.

Unlike the yellowjacket, these paper wasps are not attracted to wasp traps. Their nests must be individually destroyed with a wasp or hornet spray or some other method. It is also important to eliminate potential nesting sites before colonies are established by sealing all openings that allow access to hollow tubing or similar materials. Apply insecticide sprays when the wasps are clustered on their nests and in cool periods such as the early morning or late evening, periods when the wasps do not readily fly.

For more information about bees and wasps, including how to identify and control different species, visit, click on Extension and Outreach, then Cooperative Extension, then fact sheets, then insects, or visit

First aid for bee and wasp stings:

– Swelling and pain around the sting are typical reactions to a wasp or bee sting. These symptoms typically disappear within a few hours.

– Treat the sting with an antiseptic to prevent possible infection.

– Cool lotion or compresses may help relieve pain and swelling.

– Consider treating multiple stings with an oral antihistamine to help reduce swelling and itching.

– Honey bees, but not other bees or wasps, generally leave the stinger embedded in the skin. Remove the stinger as soon as possible by scraping – not crushing – the stinger with a fingernail or knife blade.

– About 1 percent of the U.S. population is hypersensitive to either bee or wasp venom following repeated stings. An allergic reaction can involve difficulty in breathing, dizziness, nausea and development of hives. These symptoms require immediate medical attention from a physician.

Wasps and bees in Colorado:

– Yellowjacket wasps are banded insects with alternating black and yellow or orange stripes. They are commonly mistaken for honey bees. However, unlike the honey bee, their body is hairless and more intensely colored. These wasps usually nest underground using existing hollows, but nests can be found in dark, enclosed areas of a building, such as crawl spaces or wall voids. Their nests are enclosed in a paper envelop, and the nest entrance is small and inconspicuous. Yellowjackets will sting when the nest area is disturbed. The western yellowjacket is estimated to cause at least 90 percent of the "bee stings" in Colorado.

– The most common hornet in Colorado is the baldfaced hornet. This hornet has dark and white stripes has a stout body. Hornets make large grayish paper nests in trees, shrubs and under building eaves. Hornets eat live insects and will sting if their colony is disturbed.

– Paper wasps make open-celled paper nests. Some varieties of paper wasps often nest in the open, such as under eaves. The European paper wasp will also nest in small cavities. Most paper wasps are reddish-brown with yellow; the European paper wasp is shiny black and yellow.

– The honey bee is the only bee that establishes a permanent colony. These bees are dependent upon each other and do not survive for long outside of the colony. Honey bees will swarm on sunny afternoons in May and June when they are scouting for a location to build a new home. Honey bees are not aggressive but they will defend their colony if it is disturbed; honey bees foraging around flowers do not attack. Honey bees’ stingers are barbed and embed in the skin, and when the bee stings, it leaves behind a poison sac. Once a honey bee stings, it dies. In Colorado, honey bees are important in food production because they pollinate many crops such as apples, pears, peaches and melons. The state’s honey bee annual value is usually around $20 million.

Bumble bees are native to Colorado, and there are more than two dozen different species of bumble bees in the state. All bumblebee species are heavy bodied, fuzzy and black with yellow or orange stripes. Bumble bees often nest in abandoned rodent burrows. The size of bumblebees varies according to the season. In the early season, large queens are followed by tiny worker bees. As the colony size increases, the size of the bumble bees produced also increases. New queens and males develop by the end of the summer.

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