Cooperative ExtensionDivision of Agriculture and Natural ResourcesUniversity of California

^^^ntura County800 South Victoria Avenue * Ventura, California 93009-0042 * Phone (805) 654-2924

Column Release

July 12, 1991

Nick SakimehFsunoi Advisor

YELLOW JACKETS

Yellow jackets are found throughout California. They arescavengers of protein food, but may be predators when prey isvery abundant. They are up to one inch long. The body is mostlyyellow and black striped, though the yellow may fade into whitein some species. The wings are clear. The queen waspoverwinters in a protected place and is the founder of the newcolony. When spring arrives, a small nest is built and eggs arelayed. The eggs hatch in two to five days, the larvae remain intheir cells where they are fed proteinaceous food particles andinsect parts that the queen has chewed for them. When fullgrown, the larvae spin a cocoon to emerge later as worker adults.The larval to adult process takes about one month.

The workers are infertile females that care for the nest and feedthe larvae. At this point the function of the queen becomes egglaying only. Males are produced in the fall along with newqueens. After male emergence, the queen is fertilized andquickly seeks out a place to overwinter. Usually the fertilizedqueen is the only wasp to survive the winter.

Nests are built either above ground or below ground, the choicedetermined by site availability. Nests above ground are madewith a grayish paperlike covering made with wood, foliage orcellulose debris combined with an oral secretion. Nests above

ground may be suspended or built between supporting structures.Underground nests are excavated by workers who use large amountsof water to mix with the excavated soil before the debris isdeposited outside the nest entrance. In the fall, new largercells are constructed to hold larvae for next year's queens.There are several generations per year. Populations will varygreatly from year to year due to the weather, A prolonged coldspell after the queen has started to lay eggs will significantlyreduce the population. This is one of the main reasons whymountain populations are more variable than lowland populations.

Yellowjackets are extremely protective of their nests and shouldnot be approached during the day. They can inflict multiple,painful stings if agitated or aggravated.

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Nicholas J. Sakovich, Farm Advisor

Information and progr^m^s availabte to all without discrimination. Tha University of California, in compliance with the Civil Rights Act of 1964, Title IX of the Education Amendments of 1972, and theRehabilitation Act of 1973, does not discriminate on the basis of race, creed, religion, color, national origin, sex, or mental or physical handicap in any of its programs or activities or with respect toany of its employment policies, practices, or procedures. The University of California does not discriminate on the basis of age, ancestry, sexual 'orientation, marital status, citizenship, medicalcondition (as defined in Section 12926 of the California Government Code), nor because individuals are disabled or Vietnam era veterans. Inquiries regarding this policy may be directed to thePersonnel Studies and Affirmative Action Manager, Division of Agriculture and Natural Resources, StX) Lakeside Drive, 6th Ploor, Oakland, CA 94612-3560, (415)987-0097

U.S. Department of Agriculture, University of Califomia Cooperating.

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PAPERWASPS: "Paper" wasps include the genus Polistes, and gettheir name from the papery nests they make, a feature they sharewith the yellowjackets. Like jellowjackets, they live incolonies which are formed each year by an overwintering queen,but the nest is considerably different. It is umbrella shaped,suspended from a stalk on the eaves of houses, trees, shrubbery,or other protected areas. The cells are in a single layer, openand unprotected at the bottom. The paper wasps are also veryprotective of their nests and should be approached with caution.

MUD DAUBERS: Mud daubers are also called "thread-waisted" waspsdue to their long, slender abdomen. The body is usually a singlecolor, ranging from black to metallic dark blue. The nest ismade out of mud or clay, and is attached under eaves or bridges,or against houses, barns, or sheds. Each cell has an insect orspider in it that the larvae will feed on while developing. Thisis in contrast to the yellowjackets which are fed pre-chewedfood. Mud daubers do not protect their nests and will rarelysting an intruder even though they can inflict a nasty sting.

PARASITIC WASPS: Parasitic wasps are of considerable help to thehome gardener. Brconic wasps are small and are of variouscolors. They often parasitize insect pests. The eggs aredeposited in the host and develop internally in most species.Another group of parasitic wasps, Trichgramma, parasitize a greatnumber of caterpillar eggs by feeding internally. Both speciesof wasp are extremely small, about l/16th inch (1.5 mm) long.

For control of insects, call the local Cooperative Extensionoffice at 654-2924 and request that the free leaflet 7046,Control of Yellowj ackets and Similar Wasos^ be mailed to you.All University of California Cooperative Extension programs areopen to all without discrimination.