Wasp & Yellow Jacket Statistics and Facts

Who is who

Wasp and yellow jacket species in Southern California

Most stinging wasp problems in Southern California come from two yellowjackets and a few paper wasps. Several other wasps look similar but rarely cause trouble.

1. The western yellowjacket, Vespula pensylvanica, is the most commonly encountered yellowjacket in California and is sometimes called the meat bee. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, Pub. 7450, updated 2012)
2. Besides the western yellowjacket, seven other species of Vespula occur in California, according to UC IPM. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
3. The German yellowjacket, Vespula germanica, reached Southern California in 1991 and is now part of the local fauna. (Source: UC Riverside Department of Entomology, Wasp Identification)
4. UC IPM reports that the German yellowjacket is becoming more common in many urban areas of California. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
5. Other yellowjackets found in Southern California include the California yellowjacket (Vespula sulphurea), the montane Vespula atropilosa, Vespula consobrina north of Santa Barbara, and the aerial-nesting Dolichovespula arenaria in the mountains. (Source: UC Riverside Department of Entomology, Wasp Identification)
6. Paper wasps found in California include Polistes fuscatus aurifer, Polistes apachus and the European paper wasp, Polistes dominula. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
7. Yellowjackets are 1/2 to 1 inch long with jagged yellow and black stripes; paper wasps are about 1 inch long. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
8. The European paper wasp was first reported in North America in 1978 around Boston and is now found coast to coast. (Source: Penn State Extension, European Paper Wasp, updated 2026)
9. European paper wasp queens tend to produce more workers than native paper wasps and start colonies earlier in the season. (Source: Penn State Extension, European Paper Wasp, updated 2026)
10. In a UC Davis study of European paper wasps in Northern California, the wasp crashed to barely detectable levels at all but one monitoring site by 2014-15, and no quantifiable impact on butterfly populations was found. (Source: UC Davis project reports, USDA NIFA Research Portal, 2014–2019)
11. The bald-faced hornet is not a true hornet but a yellowjacket in the genus Dolichovespula; it builds aerial nests often a foot or more in diameter. (Source: UF/IFAS Featured Creatures EENY-081, revised 2024)
12. Mud daubers are solitary wasps that build hard mud nests, unlike social yellowjackets and paper wasps. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
13. Mud daubers are 1/2 inch to just over 1 inch long and rarely sting unless threatened or touched. (Source: Clemson University HGIC, Mud Daubers)
14. The blue mud dauber, Chalybion californicum, stocks its nest mostly with black widow spiders. (Source: Texas A&M AgriLife Extension, Field Guide to Common Texas Insects: Mud Daubers)
15. UF/IFAS counts 18 Vespula yellowjacket species in the Nearctic region (North America). (Source: UF/IFAS Featured Creatures EENY-081, revised 2024)

UC Riverside's species list is described as a guide to common species, not a complete count. I could not find a primary source giving a total number of wasp species in California.

How many wasps

Yellow jacket nest size and record nests

A normal yellowjacket nest holds hundreds to thousands of wasps. In warm places a few colonies survive winter and grow far larger.

1. Yellowjacket colonies can reach populations of 1,500 to 15,000 individuals, depending on the species. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
2. Paper wasp nests rarely exceed the size of an outstretched hand and hold 15 to 200 individuals. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
3. UC Riverside entomologists say the pest yellowjackets in Southern California reach peak nest populations in the several thousands, while non-pest species peak at a few hundred wasps. (Source: UC Riverside Department of Entomology, Wasp Identification)
4. UC Riverside estimates a yellowjacket nest at maybe 1,000 to 3,000 wasps and larvae, compared with about 40,000 bees plus 20,000 larvae and pupae in a honey bee colony. (Source: UC Riverside Department of Entomology, Wasp FAQs)
5. UC Riverside puts paper wasp colonies at about 100 wasps. (Source: UC Riverside Department of Entomology, Wasp Identification)
6. Golden paper wasp nests can contain up to 200 cells with 20 to 30 adult wasps. (Source: WSU Hortsense, Vespidae fact sheet, reviewed 2026)
7. In a study cited by UF/IFAS, the largest eastern yellowjacket nest had eight levels of comb and more than 2,800 wasps. (Source: UF/IFAS Featured Creatures EENY-081, revised 2024)
8. A huge southern yellowjacket nest built around the end of a tree stump reached about 2.5 meters (8.2 feet) tall with 74 layers of comb, and may have been two or three colonies combined. (Source: UF/IFAS Featured Creatures EENY-081, revised 2024)
9. In 2006, more than 90 perennial yellowjacket super nests were reported in Alabama. Alabama Living described such a colony as holding about 15,000 wasps, versus a normal peak of 4,000 to 5,000 workers, and an Alabama Extension entomologist said these nests can have many thousands of workers, far more than an average nest. (Source: Alabama Living, 2019, quoting the Alabama Cooperative Extension System)
10. In Hawaii, where the western yellowjacket is invasive, colonies frequently become perennial with multiple queens, and some nests hold hundreds of thousands of workers. (Source: Purcell Lab, UC Riverside, research blog, 2017)
11. In a Hawaii Volcanoes National Park study, only 1 of 76 monitored western yellowjacket colonies from 2016 survived into a second season, and none of 41 from 2017 did; earlier estimates put perenniality at up to 20% of colonies in some years. (Source: Scientific Reports, 2021)
12. A Florida Museum of Natural History lepidopterist found close to 50 queens among thousands of workers in two excavated southern yellowjacket nests in cavities of 20 to 40 gallons. (Source: Florida Museum of Natural History blog, Andrei Sourakov)
13. In southern Mississippi, a small percentage of southern yellowjacket nests survive winter to become perennial nests; an annual nest may reach more than a thousand wasps. (Source: Mississippi State University Extension, Bug's Eye View, 2016)

Colony size figures vary widely. UC IPM gives 1,500 to 15,000 individuals and UC Riverside gives 1,000 to 3,000 for a typical nest. The largest counts come from perennial nests in warm climates such as Hawaii, where UC Riverside's Purcell Lab described excavating nests with hundreds of thousands of workers. The Florida Museum observation is an informal account, not a survey.

Seasons

Yearly cycle and why late summer is peak sting season

Yellowjacket colonies start from one queen in spring and peak in late summer and fall, when food gets scarce and nests are biggest.

1. A yellowjacket queen emerges in late winter to early spring to feed and start a new nest. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
2. From spring to midsummer, nests grow and workers forage mainly for protein, usually other insects. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
3. By late summer, yellowjacket colonies grow more slowly or stop growing and require large amounts of sugar to maintain the queen and workers. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
4. In fall, yellowjackets act mainly as scavengers and show up at picnics, garbage cans, pet food and ripe fruit. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
5. In autumn, colonies build larger cells for new queens; new queens mate and seek winter shelter, and the rest of the colony dies with winter's arrival. (Source: UF/IFAS Featured Creatures EENY-081, revised 2024)
6. In coastal California south of San Francisco and in very mild winters, some yellowjacket colonies survive for several years and become quite large. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
7. Researchers note that multi-year yellowjacket colonies occur only in regions with warm winters: places where Vespula is native, such as the southeastern U.S. and Southern California, and places where it was introduced, such as Hawaii, Australia and New Zealand. (Source: Scientific Reports, 2021)
8. In a Philadelphia emergency department study of 449 sting victims, August and September had the highest sting rates: 59 per 10,000 visits in August to October versus 20 in May to July. (Source: Bischof, Journal of Family Practice, 1996)
9. Washington State University notes that yellowjackets and hornets are often more aggressive than paper wasps, especially in late summer and fall. (Source: WSU Hortsense, Vespidae fact sheet, reviewed 2026)

The Philadelphia study covers one hospital in a four-season climate. It did not identify which insect caused each sting. Southern California's mild winters can stretch the season.

Sting data

Wasp and yellow jacket stings: injuries and deaths

National data usually lump bees, wasps and hornets together. The figures below are labeled by what each source counted.

1. Yellowjacket and other wasp stingers have no barbs and can be used repeatedly, especially when the wasp gets inside clothing. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
2. Unlike the honey bee, which dies after a single sting, yellowjackets and hornets may sting as often as they find a target. (Source: UF/IFAS Featured Creatures EENY-081, revised 2024)
3. A stinging yellow jacket marks the victim with an alarm pheromone that may last for hours and draw other yellow jackets. (Source: Alabama Cooperative Extension System)
4. From 2001 to 2010, U.S. emergency departments treated an estimated 26,939 wasp sting injuries per year on average. (Source: Langley et al. (CDC co-authors), Wilderness & Environmental Medicine, 2014)
5. Over the same period, hornet stings averaged an estimated 3,774 emergency department visits per year and bee stings 162,080. (Source: Langley et al. (CDC co-authors), Wilderness & Environmental Medicine, 2014)
6. Across 2001-2010, the study counted an estimated 404,115 emergency department visits for vespid stings (wasps, hornets, yellow jackets and others). (Source: Langley et al. (CDC co-authors), Wilderness & Environmental Medicine, 2014)
7. About 1.82% of all non-dog bite and sting injuries seen in emergency departments in 2001-2010 ended in hospitalization or transfer to another facility. (Source: Langley et al. (CDC co-authors), Wilderness & Environmental Medicine, 2014)
8. Annual U.S. deaths from hornet, wasp and bee stings ranged from 59 in 2012 to 89 in 2017, and 84% of deaths in 2011-2021 were among males. (Source: CDC NCHS, MMWR QuickStats, 2023)
9. From 2000 to 2017, there were 1,109 U.S. deaths from hornet, wasp and bee stings, an average of 62 per year, about 80% among males. (Source: CDC NCHS, MMWR QuickStats, 2019)
10. An estimated 3,890 people were treated in U.S. emergency departments for stings in the mouth or throat from 2004 to 2023, about 5% of all stings in the data. (Source: Huff et al., Wilderness & Environmental Medicine, 2025 (NEISS analysis))
11. Multiple-sting encounters can cause kidney damage, and patients may need medical care that can include dialysis. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
12. The Merck/MSD Manual says the average unsensitized person can safely tolerate 22 stings per kilogram of body weight. (Source: MSD Manual Professional Version, Insect Stings, 2025)

CDC death counts use a single cause-of-death code that combines hornets, wasps and bees, so yellowjacket deaths cannot be separated out. Emergency department data rely on how the visit was recorded, and many people cannot tell which insect stung them. The MSD Manual's 22 stings per kilogram figure applies to people without venom allergy; allergic people can react to a single sting.

Venom and allergy

Wasp venom versus honey bee venom, and allergy cross-reactivity

Wasp and honey bee venoms are made of different proteins, which affects allergy testing and treatment.

1. The allergy practice parameter states that cross-sensitization is extensive between hornet and yellow jacket venoms and somewhat less extensive between yellow jacket or hornet and wasp venoms. (Source: Golden et al., Stinging Insect Hypersensitivity Practice Parameter Update, Annals of Allergy, Asthma & Immunology, 2017, via AAAAI)
2. The same guideline says cross-reactivity is less common between honey bee venom and vespid venoms, though many patients test positive to both. (Source: Golden et al., Annals of Allergy, Asthma & Immunology, 2017, via AAAAI)
3. Vespid venom contains phospholipase, hyaluronidases and antigen 5, the most allergenic component; melittin is thought to be the main pain-causing part of honey bee venom. (Source: MSD Manual Professional Version, Insect Stings, 2025)
4. UC Riverside entomologists note that honey bee and yellowjacket venom proteins differ, so an allergy to one does not necessarily mean an allergy to the other. (Source: UC Riverside Department of Entomology, Wasp FAQs)
5. Between 1.6% and 5.1% of people in the U.S. are estimated to have had a life-threatening allergic reaction to an insect sting. (Source: ACAAI, Insect Sting Allergies)
6. Potentially life-threatening reactions to insect venom occur in 0.4% to 0.8% of children and 3% of adults. (Source: ACAAI, Insect Sting Allergies)
7. People who have had an allergic sting reaction have a 60% chance of a similar or worse reaction if stung again. (Source: ACAAI, Insect Sting Allergies)
8. Venom immunotherapy provides up to 98% protection against future reactions and usually lasts three to five years. (Source: ACAAI, Insect Sting Allergies)
9. ACAAI says the majority of insect stings in the U.S. come from wasps, yellow jackets, hornets and honey bees. (Source: ACAAI, Insect Sting Allergies)

This is general information from allergy societies, not medical advice. The CDC's NIOSH advises outdoor workers with a history of severe reactions to carry an epinephrine auto-injector and that anaphylaxis requires immediate emergency care.

Nest sites

Ground nests, wall voids and where yellow jackets live

Western and German yellowjackets usually nest out of sight, so people often find them by stepping on or mowing over the entrance.

1. Yellowjackets commonly nest in rodent burrows and sometimes use voids in the walls and ceilings of houses. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
2. An underground yellowjacket nest can sit quite a distance from its visible entrance hole. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
3. Ground-nest entrances are typically about the size of a nickel, and ground vibrations can provoke hundreds of yellow jackets to come out. (Source: Alabama Cooperative Extension System)
4. AAAAI says yellow jacket nests are made of a paper-like material and are usually underground, but can also be in building walls, masonry cracks or woodpiles. (Source: AAAAI, Stinging Insect Allergy)
5. Aerial yellowjacket nests hang from eaves or tree limbs with the entrance normally at the bottom. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
6. Wasps are most likely to be inside the nest at night. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
7. European paper wasps build in protected spots such as eaves, light fixtures, bird boxes, grills, RVs and boats. (Source: Penn State Extension, European Paper Wasp, updated 2026)
8. UC IPM says yellowjackets typically forage about 1/4 mile from the nest; UC Riverside says about 1 mile. (Source: UC IPM Pest Notes, 2012; UC Riverside Wasp FAQs)

Foraging range estimates differ between two University of California sources (about 1/4 mile versus about 1 mile). Range likely depends on species and food supply.

Benefits

Why wasps matter, and what pesticides can harm

Yellowjackets and paper wasps eat large numbers of pest insects and visit flowers. UC IPM recommends leaving nests alone where they do not threaten people.

1. UC IPM says social wasps should be protected and encouraged to nest in areas of little human or animal activity. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
2. Yellowjackets and hornets destroy many insects that attack cultivated and ornamental plants. (Source: UF/IFAS Featured Creatures EENY-081, revised 2024)
3. Washington State University calls wasps in the family Vespidae the most dominant generalist pollinators and says yellowjackets visit a wide range of flowers. (Source: WSU Hortsense, Vespidae fact sheet, reviewed 2026)
4. Paper wasps hunt caterpillars, beetle larvae and other prey on plants to feed their young. (Source: WSU Hortsense, Vespidae fact sheet, reviewed 2026)
5. Predators of social wasps include birds, reptiles, amphibians, skunks, raccoons, spiders and praying mantids, though none gives satisfactory control around homes. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
6. UC IPM warns that some insecticides with low toxicity to people can be highly toxic to beneficial insects such as parasitic wasps and to honey bees, earthworms and aquatic invertebrates. (Source: UC IPM, Understanding Pesticides)
7. UC IPM notes that pesticides used indoors may linger and cause unhealthy and even dangerous conditions for people and pets. (Source: UC IPM, Understanding Pesticides)
8. The yellowjacket Pest Note advises minimizing the use of pesticides that pollute waterways and harm human health, and warns that wasps will attack if they sense a poison being applied to their nest. (Source: UC IPM Pest Notes: Yellowjackets and Other Social Wasps, 2012)
9. UC Riverside entomologists note that some insecticides have been removed from sale because of high mammalian toxicity, and they advise homeowners not to try to kill a yellowjacket nest themselves. (Source: UC Riverside Department of Entomology, Wasp FAQs)

I could not find a primary source that puts a percentage on how much pollination wasps provide. The WSU statement is qualitative.

Invasive hornets

Northern giant hornet status in the U.S.

The northern giant hornet, once nicknamed the murder hornet, was detected in the U.S. in northwest Washington. Officials declared it eradicated in 2024.

1. The northern giant hornet first drew national attention in late 2019 when it was detected near Blaine, Washington. (Source: USDA APHIS, APHIS in Action: Victory Over the World's Largest Hornet Species)
2. Four northern giant hornet nests were found and destroyed in the U.S.: the first in October 2020 and three more in August and September 2021. (Source: Washington Invasive Species Council, Northern Giant Hornet)
3. 2024 marked the third straight year of surveys with no northern giant hornet detections, which led to the eradication declaration on December 18, 2024. (Source: Washington Invasive Species Council, Northern Giant Hornet)
4. Members of the public provided about half of the confirmed northern giant hornet detections. (Source: Washington Invasive Species Council; USDA APHIS)
5. The U.S. northern giant hornet nests were found mainly inside alder trees. (Source: USDA APHIS, APHIS in Action)

All four U.S. nests were found in Washington State. Large wasps people see in Southern California are usually other species, such as yellowjackets or paper wasps.

Questions

Frequently asked questions

Keep reading

Related on this site

• Wasp removal
• Yellow jacket removal
• Honey bee, yellow jacket or wasp? How to tell

How this page was made

Methodology & sources

Every fact on this page was traced to a primary source (a government data release, a university research or extension publication, a professional medical body or a peer-reviewed paper) and checked against the original document. Data years are given where they differ from publication years. Where reputable sources disagree, both figures are shown. Sources are named in plain text next to each fact.

• UC Statewide Integrated Pest Management Program (UC IPM), Pest Notes: Yellowjackets and Other Social Wasps, Pub. 7450
• UC IPM, Understanding Pesticides
• UC Riverside Department of Entomology, Wasp Identification and Wasp FAQs
• Purcell Lab, UC Riverside
• UC Davis European paper wasp project, USDA NIFA Research Portal
• UF/IFAS Featured Creatures EENY-081, Yellowjackets and Hornets
• Florida Museum of Natural History
• Penn State Extension, European Paper Wasp
• Washington State University Hortsense
• Clemson University Home & Garden Information Center
• Texas A&M AgriLife Extension
• Alabama Cooperative Extension System
• Mississippi State University Extension
• Scientific Reports (2021)
• CDC National Center for Health Statistics, MMWR QuickStats
• Langley et al., Wilderness & Environmental Medicine (2014)
• Huff et al., Wilderness & Environmental Medicine (2025)
• Bischof, Journal of Family Practice (1996)
• CDC NIOSH, Insects and Scorpions
• American College of Allergy, Asthma and Immunology (ACAAI)
• American Academy of Allergy, Asthma & Immunology (AAAAI)
• Golden et al., Stinging Insect Hypersensitivity Practice Parameter, Annals of Allergy, Asthma & Immunology (2017)
• MSD Manual Professional Version
• USDA APHIS
• Washington Invasive Species Council