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Identification and Lifecycle
In western states there are two distinct types of social wasps:
yellowjackets and paper wasps. Yellowjackets are by far the most
troublesome group. Paper wasps are much less defensive and rarely
sting humans. They tend to shy away from human activity except
when their nests are located near doors, windows, or other high
traffic areas.
Nests of both yellowjacket and paper wasps typically are begun in
spring by a single queen who overwinters and becomes active when
the weather warms. She emerges in late winter/early spring to feed
and start a new nest. From spring to midsummer nests are in the
growth phase, and the larvae require large amounts of protein.
Workers forage mainly for protein at this time (usually in the
form of other insects) and for some sugars. By late summer,
however, the colonies grow more slowly or cease growth and require
large amounts of sugar to maintain the queen and workers. So
foraging wasps are particularly interested in sweet things at this
time.
Normally, yellowjacket and paper wasp colonies only live one
season. In very mild winters or in coastal California south of San
Francisco, however, some yellowjacket colonies survive for several
years and become quite large.
Yellowjackets:
The term yellowjacket refers to a number of different species of
wasps in the genera Vespula and Dolichovespula (family Vespidae).
Included in this group of ground-nesting species are the western
yellowjacket, Vespula pensylvanica, which is the most commonly
encountered species and is sometimes called the "meat bee," and
seven other species of Vespula. Vespula vulgaris is common in
rotted tree stumps at higher elevations and V. germanica (the
German yellowjacket) is becoming more common in many urban areas
of California, where it frequently nests in houses. These wasps
tend to be medium sized and black with jagged bands of bright
yellow (or white in the case of the aerial- |
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nesting Dolichovespula
[=Vespula] maculata) on the abdomen, and have a very short, narrow
waist (the area where the thorax attaches to the abdomen).
Nests are commonly built in rodent burrows, but other protected
cavities, like voids in walls and ceilings of houses, sometimes are
selected as nesting sites. Colonies, which are begun each spring by a
single reproductive female, can reach populations of between 1,500 and
15,000 individuals, depending on the species. The wasps build a nest
of paper made from fibers scraped from wood mixed with saliva. It is
built as multiple tiers of vertical cells, similar to nests of paper
wasps, but enclosed by a paper envelope around the outside that
usually contains a single entrance hole. If the rodent hole is not
spacious enough, yellowjackets will increase the size by moistening
the soil and digging. Similar behavior inside a house sometimes leads
to a wet patch that develops into a hole in a wall or ceiling.
Immature yellowjackets are white, grublike larvae that become white
pupae. The pupae develop adult coloring just before they emerge as
adult wasps. Immatures are not normally seen unless the nest is torn
open or a sudden loss of adult caretakers leads to an exodus of
starving larvae.
Aerial-nesting yellowjackets, Dolichovespula arenaria and D. maculata,
build paper nests that are attached to the eaves of a building or are
hanging from the limb of a tree. The entrance is normally a hole at
the bottom of the nest. These aerial nesters do not become scavengers
at the end of the season, but they are extremely defensive when their
nests are disturbed. Defending D. arenaria sometimes bite and/or
sting, simultaneously. Wasp stingers have no barbs and can be used
repeatedly, especially when the wasp gets inside clothing. As with any
stinging incident, it is best to leave the area of the nest site as
quickly as possible if wasps start stinging.
Paper Wasps:
Paper wasps such as Polistes fuscatus aurifer, P. apachus, and P.
dominulus are large (1-inch long), slender wasps with long legs and a
distinct, slender waist. Background colors vary, but most western
species tend to be golden brown, or darker, with large patches of
yellow or red. Preferring to live in or near orchards or vineyards,
they hang their paper nests in protected areas, such as under eaves,
in attics, or under tree branches or vines. Each nest hangs like an
open umbrella from a pedicel (stalk) and has open cells that can be
seen from beneath the nest. White, legless, grublike larvae sometimes
can be seen from below. Paper wasp nests rarely exceed the size of an
outstretched hand and populations vary between 15 to 200 individuals.
Most species are relatively unaggressive, but they can be a problem
when they nest over doorways or in other areas of human activity, such
as fruit trees.
Mud Daubers:
Mud daubers are black and yellow, thread-waisted, solitary wasps that
build a hard mud nest, usually on ceilings and walls, attended by a
single female wasp. They belong to the family Sphecidae and are not
social wasps but may be confused with them. They do not defend their
nests and rarely sting. During winter, you can safely remove the nests
without spraying.
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