Yellowjackets are stinging insects that build large communal
hives. Three kinds of yellowjackets occur in San Mateo County:
the Western Yellowjacket (Vespula pensylvanica), Common
Yellowjacket (Vespula alascensis) and the Aerial Yellowjacket
(Dolichovespula arenaria). The first two build hives under the
ground and feed on live insects, dead animals, and nectar. These
are the insects that pester you during your summer and fall BBQs.
Aerial yellowjackets build large paper nests in trees or other
high places (such as the eaves of your house).
Paper wasps are similar to muddaubers. Females are solitary and
build small nests from paper. These nests often appear along the
eaves of homes during summer months. They are papery, two to four
inches across, and have a honeycomb appearance when viewed from
Muddaubers belong to the family Sphecidae. They have a
very thin waist and long, dangly legs. These wasps are incredibly
beautiful, with smoky wings and a bright metallic blue body.
There are more than 1,100 species in this family in North
America. All are solitary with each female building an individual
nest in which to lay her eggs. The nests are made out of mud, two
to three inches across, with rows of round cells containing the
developing embryos. The female wasp stocks each cell with a
spider—food for the young wasps when they hatch.