European Paper Wasp Fact Sheet No

European Paper Wasp Fact Sheet No. 5.611 Insect Series|Home and Garden by W. Cranshaw* The European paper wasp, Polistes Quick Facts dominula, is a newly established insect now abundant in many areas of Colorado. The • European paper wasps paper nests of this wasp are commonly do not produce nuisance observed in yards and gardens and the problems around outdoor wasp is involved in stinging incidents. dining however they can The European paper wasp develops as a sting. predator of caterpillars and some other insects, populations of which have probably • European paper wasps have been affected by the establishment of this become one of the most new wasp. important natural controls Figure 1: European paper wasp. of many kinds of yard and Description garden insects. The European paper wasp is a generally • The European paper wasp is black insect marked with yellow. They are a social insect that produces fairly slender-bodied insects with a distinct an annual colony in a paper constriction of the body between the thorax nest. Individual colonies and abdomen. are established anew each The European paper wasp is superficially spring. similar to and commonly mistaken for various yellowjackets (Vespula spp.). Several • European paper wasps are yellowjacket species are native to Colorado sometimes mistaken for and these historically have been the most yellowjackets or hornets. significant stinging insects of the region. A somewhat blunter, more compact body Figure 2: Western yellowjacket, the most common form distinguishes yellowjackets from the species mistaken for European paper wasp. European paper wasp. Also, the long hind legs of paper wasps tend to trail below when record dates from 1995, suggest western the insects are in flight. Colorado may have been colonized earlier. Wherever it has established, the European paper wasp has usually become a common Background of Colorado species within a few years. Currently it is Introduction now considered very abundant in every The European paper wasp is the common urbanized county in eastern Colorado paper wasp of Europe. It was first found in and the three western Colorado counties North America in the 1970s in the Boston of Mesa, Montrose, and Delta. Presently area. Since then it has spread rapidly to much it is not thought to occur in much of the of the northern half of the United States higher elevation counties, but is known in and British Columbia. The first Colorado Steamboat Springs. record for the species is August, 2001 from © Colorado State University Larimer County, and it likely entered eastern Life History and Habits Colorado shortly before 2000. The first Utah Extension. 4/08. Revised 6/13. The European paper wasp is a social www.ext.colostate.edu insect that produces an annual colony in a *W. Cranshaw Colorado State University Extension paper nest. Individual colonies are established entomology specialist, and professor, bioagricultural anew each spring. The overwintering stage sciences and pest management. 6/2013 are females (queens), only slightly larger of nest sites are particularly favored. (New than the wasps typically observed during nests sometimes are established at the summer. Female wasps that were fertilized same site the following year.) Dark cavities the previous fall survive winter in protected are often used, including those found sites in and around a yard. When they in outdoor grills, large bells, pipes, rock emerge from overwintering shelters, they cavities, and hollow spaces behind walls. may be seen on warm days as they seek Nests are also commonly attached to wood sites to establish new nests. Earliest activity on the underside of porch decks, eaves of is sometimes seen in the first half of March. homes or other overhangs. Nests are almost Nests are constructed of paper, always attached to either wood, roughened produced from chewed wood fibers metal surfaces, or rock. Figure 3: European paper wasp gnawing on of weathered fences, porch decks and Paper wasp nests are not covered weathered wood. similar sites. Initially, a few hexagonal with a surrounding envelope of paper. paper cells are formed and eggs laid in Paper envelopes that surround a nest are the cells. Upon hatch, the wasp larvae are characteristic of yellowjackets (Vespula fed crushed insects, usually caterpillars, spp.) and hornets (Dolichovespula spp.), that the overwintered queen discovers in the other social wasps found in Colorado. foraging trips among nearby plants. When Yellowjackets nest underground or, full grown the larvae then seal over the occasionally, behind walls; hornets make cell and pupate. Development of the wasps conspicuous football-sized nests attached to to the adult form is usually completed in branches or under eaves. 3 to 4 weeks after eggs are laid. The new The European paper wasp is capable wasps assist in colony activities of nest of stinging. Among the stinging insects construction, foraging, and caring for found in the state European paper Figure 4: Developing wasp larvae and capped young. The original queen increasingly wasp is relatively non-aggressive, and pupae. remains restricted to the nest as new somewhat less likely to sting than are workers take over colony activities. most yellowjackets and bumble bees. The colony continues to grow through Stings from European paper wasp the summer and may contain several occur almost exclusively when nests are dozen individuals by the end of summer. accidentally disturbed. The nest is continuously expanded and European paper wasps rear their young reconstructed through the summer and on live insects. They do not produce may contain a hundred or more cells by nuisance problems around outdoor dining fall. A few of the wasps produced later that characterize scavenging species, such in summer are males and increasing as the western yellowjacket. European numbers of the females become sexually paper wasps will sometimes feed on sweet mature at that same time. Mating occurs materials, including honeydew produced Figure 5: European paper wasp at nest. and the mated females are the surviving by aphids. On rare occasions, they also may overwintering stage. Males and non- feed and damage ripe fruit. This habit is reproductive females do not survive winter particularly notable in cherries and some and the nest is abandoned by late fall. other well-ripened stone fruits grown The fertilized overwintering females on the West Slope, where they may be seek protected sites for shelter during the serious pests. cold season. Often they find winter shelter European paper wasps have become outdoors but occasionally they will find one of the most important natural controls suitable areas behind walls or in other of many kinds of yard and garden insects. areas of the house. These wasps sometimes Most commonly they feed on caterpillars, will move about during warm periods including the larvae of hornworms, and may find themselves within the living cabbageworms, and tent caterpillars. Sawfly space. Such wintertime encounters do not larvae are also commonly taken prey. indicate the presence of an active nest, (European paper wasps can be only that some wasps have found some encouraged to nest in nest boxes. Artificial Figure 6: European paper wasps nesting in clothes line. pocket of winter shelter within the building. nest sites can be useful if one wants the Overwintered females emerge from these benefits of these insects with a known nest areas in spring and search out sites to location so accidental disturbances can be establish nests in the neighborhood. avoided. A typical nest box would be made Nests are almost always established in of wood and at least 4-in x 4-in x 4-in, open new locations each year and several kinds at the bottom. They should be mounted several feet above ground on a solid post.) Control of European Other Paper Wasps Paper Wasp of Colorado If nests are not in a location where they Three other species of paper wasps are likely to be disturbed, it is usually best are native to the state – Polistes fuscatus to leave them in place. The nests will be (golden paper wasp), Polistes apachus abandoned at the end of the season and and Mischocytarssus flavitarsus (western they then can be safely removed. paper wasp). There is no evidence that Individual nests can be destroyed. the new species has significantly affected Insecticides are often used for this purpose their activities. In rural areas, away from and a wide variety of “wasp and hornet” buildings and human structures, these Figure 7: A nest box designed to house European paper wasp. marketed products are effective. If nests native paper wasps are the predominant are treated it is recommended to apply species of paper wasp one will likely treatments in the evening. At this time most find. All of these other paper wasps have of the wasps have returned to the nest so generally similar biologies to the European that they can be killed and, after dark, flying paper wasp. activities are greatly reduced. After the nest has been killed it should be removed and destroyed. This will eliminate larvae that were within capped cells during spraying. These usually survive and later will emerge. It is also recommended that after a nest is removed the area also be washed with a jet of water to eliminate colony odors. These Figure 8: European paper wasps in nest box. practices will inhibit surviving wasps, not present on the nest when it was destroyed, from attempting to reestablish a nest upon return. There are no traps or lures that can be used to control this species. Commercially available ‘wasp traps’ are designed to attract certain kinds of yellowjackets and contain baits such as fruit juices, fresh meat, or Figure 11: Western paper wasp, Mischocytarsus heptyl butyrate (found in many retail wasp flavitarsus. lures). None of these are attractive to the European paper wasp.

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