Paper & Mud Wasps
In the Northwest we have several species of paper wasps & mud wasps, or mud daubers. Most are black & yellow, but some mud wasps are black with a metallic blue tint to them.
Paper wasps make small nests out of wood fibers & are commonly found under the eaves or in the attic of houses & buildings. Their nests are open & the honeycomb shaped cells are exposed. Usually wasp nests are quite small (the size of a dime to hand size). Paper wasps start their nests in the spring. A queen starts each nest & then raises workers. A huge nest of paper wasps might get to be seventy-five in numbers, but most nests may have only twenty to forty wasps on them. At the end of their cycle the queen raises other queens for next year. Those queens leave the nest to find a place to hibernate for the winter (usually in attics of houses) while the original nest dies; the cycle then starts again next spring with the new queens. Paper wasps can reuse old nests from a previous year, so any visible nests under your eaves should be knocked down.
Mud wasps are very similar to paper wasps except that they build their nests out of mud (surprise!). Mud wasps will make a nest resembling a dirt clod, lay eggs in it, leave food for the larva, & then seal the cells. Those eggs will hatch out the next spring.
Wasps are very beneficial insects. They are typically not aggressive & won't do any damage to your home. They use their stinger to paralyze insects to eat (they don't eat dead meat so they're not the guys bugging you at your barbeque), however, you can be stung if you swat at one or step on it barefoot. With wasps you have three choices: let nature be & leave them alone (enjoy having less spiders around), knock them down yourself, or hire an exterminator to knock them down for you. It's not absolutely necessary to spray the nests before knocking them down. Yes, they will rebuild, but eventually they'll get the idea they can't keep a nest going & they'll move on.