Yellowjackets of California
General Information
Yellowjackets are social insects that live in a nest. They are medium sized black wasps with yellow or white markings. Depending on the type of yellowjacket, they build aerial (in the air) or subterranean nests (below ground). Aerial nests are built in trees, on utility poles, or house eaves. Subterranean nests are constructed in rodent burrows, tree cavities or ground holes. When a nest is disturbed yellowjackets can sting multiple times. These stings are painful and may be life threatening to individuals hypersensitive to the venom. In late summer months when yellowjacket populations increase they can create a nuisance in parks by scavenging for food in picnic areas. They can cause structural damage to a home when they construct nests in walls or attics. Not all yellowjackets are pests as the adults of some species are beneficial to man because they prey on flies and other insects.
Yellowjacket Nests
Yellowjackets
use vegetable fibers from trees and shrubs to produce a paper-like material for
nest construction. Inside the nest
is a series of suspended combs that contain cells where young are reared.
The combs are enclosed inside on or more layers of
a paper envelope. The surface of
the envelope is gray with tan and yellow stripes and has a scalloped texture.
Yellowjacket Castes
Nests contain three types of yellowjackets:
-
Worker: The workers forage for food, feed young, and continues to build the nest
-
Queen: The queen is the only type of yellowjacket who survives the winter. In the spring she establishes a nest and lays eggs for the rest of her life.
-
Drone: The drone (male) is only responsible for mating with a queen he does not survive the winter.
Common California Yellowjackets
Western Yellowjacket (Vespula pensylvanica)
This yellowjacket is a major pest species in
California. It is primarily a scavenger and in the summer months adults
are common around garbage receptacles in picnic areas. Nests are usually constructed in abandoned rodent burrows or
in house walls and attics. Nests
contain 500 to 5,000 workers and start to decline in late September to October.
Common Yellowjacket (Vespula vulgaris)
This yellowjacket can be a pest because adults are attracted to protein or sugar sources. This species is also considered a beneficial organism because workers prey on caterpillars and other insects. Nests are mostly subterranean but can be constructed inside house walls or in aerial locations. Nests are large and contain 500 to 5,000 workers. Nests remain active until September to December.
Bald Faced Hornet (Dolichovespula maculata)
This cream and black colored wasp lives in wooded regions in Northern California. It is a summertime pest in recreational as well as suburban areas. This species constructs a football-shaped nest attached to trees and buildings. Foragers are present from June to October.
Prairie Yellowjacket (Vespula atropilosa)
This yellowjacket is not a pest. It feeds on live insects, helping to control flies or caterpillars. Nests are constructed in the ground in open areas like grasslands or golf courses. Nests contain 75 to 400 workers and start to decline in late August to September.
Aerial Yellowjacket (Dolichovespula arenaria)
This yellowjacket is a beneficial organism. Workers prey on flies and caterpillars and rarely scavenge. They build small aerial nests that contain 100 to 700 workers. Nests begin to decline in July to September.
Yellowjacket Control
In the summer months foraging yellowjackets
may become a nuisance in parks, campgrounds and other recreational areas.
Yellowjacket populations have been managed by:
Sanitation- This is the most
effective method of controlling foraging adults.
Tightly covering all waste food sources and moving garbage receptacles
away from eating areas reduces food available to foraging workers.
Eliminating standing water sources helps to reduce the water available
for cooling the nest and drinking.
Trapping- Bait traps should be set in
April to capture future queens. Some
commercially available traps use a chemical lure to attract foraging
yellowjackets into a container with a one way passage.
Once inside, the insect cannot escape and dies.
Traps should be placed in areas away from food and people.
Nest Control- Underground nests may
be treated at night when yellowjacket activity is low due to cooler
temperatures. Follow label
directions carefully on an approved pesticide. Cover
entrances after treatment. Call a
private pest control company when an aerial nest is involved.
Similar stinging insects
Paper Wasp:
Large insect, brownish-red with yellow marking and amber wings.
Builds circular nest with a single horizontal comb on building eves.
Mud Dauber: Medium-sized insect, black to brown with yellow markings. They are distinguished from yellowjackets by the long thin structure that connects the abdomen with the body. Builds nests from soil on building eaves.
If you discover a yellowjacket nest:
AVOID THE AREA- Keep children and pets away from the nest
NOTIFY a pest control company or
governmental authorities
If you are attacked by yellowjackets
LEAVE AREA QUICKLY – Attack could last until victim leaves the area
COVER FACE- Use clothes to protect eyes and
mouth from yellowjackets
FIRST AID FOR YELLOWJACKET STINGS
For any sting- Wash with soap and cold water
For allergic reactions- As soon as possible seek professional medical care and watch for breathing difficulties
For multiple stings or hypersensitive
individuals- Immediately get professional medical care!
Do not wait for symptoms to develop!!
Here are some articles John Albright, Biologist - Public Information Specialist, wrote in 1997 about Yellowjackets:
Yellowjackets--More Than Just a Bad Fashion Statement
1997 - 1999 Yellowjacket Project Summary
The information in this web page is also available in a brochure.
For More Information:
(530) 365-3768