The days are getting longer, the sun is getting warmer, and pretty soon you are going to notice one of the creatures on the right flying against a window in your home, trying to get out. What are they? They are wasps. The bottom one is the ordinary paper wasp and the top one is the Mediterranean wasp, an introduced species which is slowly pushing our native wasp out. The Mediterranean wasp is very easily and often confused with a yellow jacket, but they are entirely different. They build unenclosed nests similar to the ones pictured below. They overwinter in attics and walls, and as the weather warms, they come out of their winter dormancy, and will sometimes find their way into the living area of your home. When this happens, they fly right to a window, because they want to get outside. Once the weather gets warm, and stays warm, they won't be problem inside anymore. They are not particularly aggressive, but can and will sting if provoked. They start building their nests, which are made out of paper, as soon as the weather starts getting warm. They normally start new nests each year, but may use old ones sometimes. They may build a new nest right next to an old one, giving the impression they are using the old one. Sometimes they can be found flying around untreated decks, old wooden fences, wood piles, etc. and no nest is found. What are they doing? They are getting wood fibers to use to make the paper for their nests.
A unique trait of wasps is that any female can become the queen. This presents a problem when trying to get rid of an existing nest, because if every wasp is not "at home" when the treatment is done. Any returning female can "declare" herself the new queen and the nest will continue on in the same location.
For nesting locations, they like areas behind shutters, enclosed light fixtures open at the bottom, the louvers at the peak of the house, under the rake board (the trim board that follows the edge of the roof at the ends of the house), and in the open ends of pipes on portable basketball backboards.
We can do prevention treatments which will drastically cut down on or totally eliminate them from building nests on and around your home. The treatments are guaranteed for the season, and should be done every year. After 2-3 years the treatment will become close to 100% effective.