Yellow jackets are medium sized wasps about half an inch long. Their black bodies have distinctive bands of bright yellow on their abdomen. They have a lance-like stinger and can sting repeatedly when attacking a perceived threat.
Yellow jackets can cause serious problems because they sometimes sting in swarms when their nest is disturbed. Ground nests are common but they can be found in walls and other void areas around the house. Some species will build an aerial nest that hangs freely from tree limbs or other high places. The nest consists of a queen and up to hundreds or thousands of workers with the nest getting larger as the warmer seasons progress. Each winter most nests die off and overwintering queens begin each spring building a new nest and hatching a new brood of yellow jackets.
Yellow jackets can be found scavenging food (plants and meat) in a variety of places. At certain times of the year many individual yellow jackets can be found around your property inspecting plants for bugs to eat or the right kind of plant material to chew up to build their nests. Keep garbage cans closed and avoid having standing water around as both of these will attract yellow jackets. If one comes close or appears threatening, simply walk away calmly until it loses interest in you.
Control of a yellow jacket nest should be taken care of by a professional. Call Alameda County Vector Control or a local pest management professional to help with the removal of yellow jacket nests.