Missouri is home to dozens of wasp species. Most wasp species are not aggressive. Wasps are scavengers or predators and generally will leave you alone if you leave them alone, but a few species can be aggressive if encountered near a garden. Only females have stingers; they can sting repeatedly because their stingers are smooth. Some wasp species prey on field and garden insects while others are scavengers that feed on trash such as food scraps and rotting fruit.
Missouri is home to three yellowjacket species. They are the eastern yellowjacket (Vespula maculifrons), southern yellowjacket (Vespula squamosa), and German yellowjacket (Vespula germanica). All three are similar in appearance with yellow-and-black-striped body markings. They are about 1/2 inch long and deliver a painful sting. Yellowjackets are scavengers.
The eastern and southern species typically build paper nests in underground holes while the German species typically nests in crevices above ground. Their nests can become basketball-size and may contain up to 5,000 insects.
The baldfaced hornet (Dolichovespula maculata) is another stinging wasp common in Missouri. It is about 3/4 inch long with a black body, white transverse stripes on the abdomen and a head that is white except for the black eyes.
Baldfaced hornets build a rounded, baseball-to-basketball-size nest of papery gray fiber material under a roof overhang or in dense shrubbery or trees. They will swarm out to defend their nest fiercely if it is disturbed. They prey on other insects for themselves and their larvae.
Missouri has at least eight species of paper wasps of the genus Polistes. They all grow roughly 1/2 inch to 1 inch long with markings of rusty brown, dull red and/or yellow. They all fly with their legs dangling and can deliver a painful sting.
Paper wasps build a single-comb, umbrella-shaped, paper nest that faces downward in a recessed, protected area such as under a building eave, deck or porch. Each nest may contain up to a few dozen insects. Paper wasps are predators that prey mainly on small caterpillars to feed their larvae. Adult paper wasps nourish themselves with flower nectar and fruit juices.
Three species of mud dauber wasp are in Missouri. They all are slender, solitary wasps that grow about 1/2 inch to 1 inch long with distinctive, long, threadlike waists. They build nests of mud under building eaves and other sheltered places. They don’t sting humans unless severely provoked.
The black-and-yellow mud dauber (Sceliphron caementarium) builds ball-shaped nest cells. The organ pipe mud dauber (Trypoxylon politum) is black with blue wings and white hind legs and builds a nest consisting of vertical, parallel rows of nest cells and resembling an old-time pipe organ. The blue mud dauber (Chalybion californicum) is metallic blue with clear wings. It reuses the old mud nests of the other two species. These three species feed mainly on spiders and put paralyzed spiders in their nests to feed their larvae.
One large Missouri wasp species, the cicada killer wasp (Sphecius speciosus), can grow 2 inches long. It has rusty but clear wings and prominent black and yellow transverse abdominal markings. Cicada killer wasps are not aggressive toward people.
The stingerless male guards the nest territory while the female digs a nest tunnel in soil in an open area such as a lawn or pasture. Adults are nectar feeders. Females hunt cicadas, sting them to paralyze them, take them to the nests, lay eggs on them and seal them in nest chambers. A nest may have 10 chambers. The larvae eat the cicadas, spend winter in the nests and emerge as adults the next spring.
The mated queens of communal wasps and hornets hibernate through winter while the workers die. The next spring, the queens revive, and each builds a nest and lays eggs in its cells; the eggs develop into the first worker wasps in four to six weeks. Workers expand the nest and forage for food while the queen lays more eggs that develop into adult workers. At summer’s end, the old queen produces new queens and male wasps that fly off to mate. The mated queens hibernate through winter and repeat the cycle the next spring.
Mud daubers form mated pairs. The male guards the nest while the female hunts for prey. Winter kills the adults but not pupae in the mud nest. They emerge the next spring to repeat the cycle.
Before using insecticides to kill wasps, put on long work pants and a heavy work shirt with long sleeves. Wear a hat, eye protection and rubber work gloves. Button your shirt sleeves and the shirt to the neck. Wear socks and work shoes or boots. After applying the insecticide, remove the clothing and wash it separately from other garments.
Eradicate nests of paper wasps and hornets located near human activity or homes with a ready-to-use aerosol insecticide spray containing carbaryl, diazinon or acephate. Wait until late evening, and then liberally spray the insecticide into the nest and get away. Observe the nest the next day. If you still see live wasps, repeat the spray treatment that evening.
For ground-nesting yellowjackets, squirt a ready-to-use insecticidal dust containing carbaryl or chlorpyrifos into the nest entrance. Do this on a dry evening when no rain is expected. If there are survivors, repeat the treatment the next night. Cover the entrance with soil.