Quick Answer
Yellow jacket nests can contain anywhere from a few hundred to several thousand yellow jackets depending on the size and maturity of the nest. A typical underground nest may contain 2,000-4,000 yellow jackets.
Yellow jackets (Vespula species) are social wasps that build intricate underground paper nests each year to house their colonies. These nests are started in the spring by a single queen who overwinters and emerges to start a new colony. She builds up the nest by laying eggs and caring for the larvae that hatch. As the colony grows over the summer months, the nest expands to contain hundreds or thousands of yellow jackets by late summer/fall when the nests reach peak size. Determining exactly how many yellow jackets occupy an underground nest can be challenging, but estimates can be made based on typical colony sizes.
Typical Yellow Jacket Colony Development
In the early spring, overwintered yellow jacket queens emerge from hibernation and begin searching for suitable nest sites. Preferred locations include abandoned rodent burrows, cavities in trees or logs, spaces under stones, and cracks or holes in the ground. Once a site is chosen, the queen begins constructing a small paper nest made from chewed wood fibers mixed with saliva. She lays eggs in the initial nest cells, and tends to the larvae when they hatch. These first offspring become worker yellow jackets who take over nest expansion, foraging, and helping care for larvae.
The colony grows exponentially through the summer as more workers are added. Peak colony size is typically reached by late summer or early fall before the annual cycle ends. Nest expansion slows and then stops, new queens and males are produced, and the original queen eventually dies. In mild climates, colonies may persist into winter but most aboveground members of the colony die off when cold weather arrives. Only newly fertilized queens overwinter to begin the cycle again next spring.
Typical Yellow Jacket Colony Size
The number of worker yellow jackets in a mature belowground nest depends on various factors like the species, location, weather/climate, and availability of food. However published estimates indicate that a typical established underground yellow jacket colony may contain approximately:
– 2,000 – 5,000 workers in Vespula squamosa colonies
– 2,000 – 4,000 workers in V. vulgaris colonies
– 4,000 – 5,000 workers in V. pensylvanica colonies
Larger, mature V. pensylvanica nests late in the season may sometimes contain up to 15,000 workers according to some sources. But averages are usually in the range of 2,000 – 5,000 workers for most species and nest locations.
Nest Size Factors
The major factors that influence yellow jacket colony sizes include:
– Species – Some yellow jacket species naturally produce larger colonies than others. V. pensylvanica tends to build the largest nests.
– Age of nest – Older, well established nests that have grown all summer long contain more yellow jackets than new nests started that same year.
– Geographic location – Nests in warmer climates with longer active seasons may grow larger than those in colder areas.
– Food availability – Better foraging conditions allow larger colonies to be supported. More food = more yellow jackets.
– Nest disturbance – Damage to nests can halt growth and reduce final numbers. Undamaged nests become much larger.
– Nest site – Larger cavities allow bigger nest construction. Small crannies limit nest size.
– Queen health/genetics – Strong, healthy queens lay more eggs and produce larger colonies. Weaker queens result in smaller nest sizes.
So in ideal conditions with abundant food sources, a large cavity site, healthy queen, etc. yellow jacket nests can reach their maximum sizes. But suboptimal conditions can restrict growth and result in smaller peak populations in the range of a few hundred up to 2000 yellow jackets for an average belowground colony.
Estimating Yellow Jacket Nest Populations
Actually determining the exact number of yellow jackets occupying an active underground nest is quite difficult. The nests are usually completely concealed, rapidly growing, and constantly fluctuating in size as workers come and go. So entomologists rely on collecting data and making estimates based on excavated nest dimensions along with typical worker densities.
Some methods used to estimate colony sizes include:
Excavation Counts
Researchers have dug up and carefully excavated entire yellow jacket nests at different times during colony development. The numbers of capped brood cells and adult workers can be directly counted in small nests, or estimated by measuring nest volume and multiplying by typical worker densities. For example, a 1995 study excavated multiple Vespula pensylvanica nests in Hawaii and found worker numbers ranging from 1,183 up to 15,333 per nest depending on the time of collection. The number of workers correlated with the belowground nest volume.
Mark and Recapture Methods
By capturing yellow jackets at the nest entrance, uniquely marking them, releasing them back into the nest, and later recapturing some of the marked insects, population size can be estimated mathematically. The proportion of marked vs. unmarked individuals recaptured provides data to calculate the total population size. This technique avoids fully excavating nests, but does involve some disturbance at the nest entrance.
Visual Estimates
The activity and traffic at a yellow jacket nest entrance provides clues about the relative size of the colony. More frequent arrivals and departures of foragers indicates a populous colony. Counting incoming/outgoing wasps for a period of time allows a rough visual estimate of hundreds vs. thousands of workers. However, this method is subjective and quite variable.
Nest Dimensions and Volumes
Examining nest architecture and carefully excavating portions of nests allows measurement of the dimensions, chambers, and total nest volume. By calculating the nest volume and multiplying by typical worker densities per cubic centimeter, the likely population can be estimated. Ranges of 0.25 – 1.5 workers per cubic centimeter have been reported in various yellow jacket nest studies.
Typical Worker Densities
Several studies have measured yellow jacket nests and counted workers to determine typical worker densities for belowground nests. Reported densities include:
– V. pensylvanica – 0.25 to 1.5 workers per cm3
– V. vulgaris – 0.25 to 0.5 workers per cm3
– V. germanica – 0.5 to 1 workers per cm3
Higher densities are found in the brood combs while lower densities occur in outer envelope layers. The overall average is generally around 0.5 workers per cm3. By taking detailed nest measurements and multiplying interior volume by density, reasonable worker population estimates can be made without fully excavating nests.
Estimating Nest Populations Example
Here is an example of how nest dimensions and worker density data can be used to estimate yellow jacket colony size:
– A Vespula pensylvanica nest is carefully excavated and found to be spherical shaped with a diameter of 30 cm.
– The volume of a sphere is (4/3)πr3. So this nest has an interior volume of approximately 14,137 cm3.
– Published worker densities for V. pensylvanica range from 0.25 to 1.5 per cm3.
– Using the average density of 0.5 per cm3 yields an estimated colony size of:
– 14,137 cm3 x 0.5 workers/cm3 = 7,068 worker yellow jackets
So for this example nest, the population estimate would be approximately 7,000 workers, which aligns with typical figures reported in research studies. By taking detailed measurements and using published worker density ranges, reasonable yellow jacket nest population estimates can be made without fully excavating nests.
Largest Known Yellow Jacket Nests
While 2,000 – 5,000 workers may be typical for most belowground yellow jacket nests, some extraordinarily large nests have been documented with huge populations:
New Zealand:
– A Vespula vulgaris nest discovered in New Zealand in 1963 contained an estimated 12,000 worker wasps.
– Another nest found there in 1980 measured over 6 feet (1.8m) across and held over 22,000 wasps.
Florida:
– In 2021, a giant Vespula squamosa nest discovered in Florida contained over 15,000 wasps. It was described as a “world record nest”.
So while uncommon, yellow jacket nests can occasionally reach sizes of 15,000 – 20,000 workers or more under ideal conditions. However, average mature nests in most regions contain 2,000 – 5,000 yellow jackets.
Nest Populations Through Season
It’s important to note that yellow jacket colonies do not reach peak size until late summer or fall. Nests grow over the course of the warm season. A summary of typical nest sizes through the seasons is:
Spring:
– Nest initiated by single queen – <100 workers by early summer
Summer:
– Rapid growth phase – hundreds to low thousands of workers by mid-summer
Late Summer/Fall:
– Peak population size reached – thousands of workers in mature nests
Winter:
– Most workers die off when cold arrives – only new queens survive
So earlier in the year, nests will have significantly fewer yellow jackets compared to peak late season numbers. The population builds up over many months to reach maximum capacity.
Conclusion
Estimating yellow jacket populations in concealed underground nests is challenging. However based on decades of research and nest excavation data, some general guidelines for typical colony sizes can be summarized as:
– Average mature nests contain approximately 2,000 – 5,000 workers
– Larger, well established nests may hold upwards of 15,000 yellow jackets
– Smaller, weaker colonies can have a few hundred workers
– Populations grow over the season, reaching peak size in late summer/fall
– Many factors impact final nest size including species, location, weather, food availability and more
While difficult to examine directly, taking detailed measurements and observations of nest dimensions, traffic, and entrance activity can allow reasonable estimates of yellow jacket numbers to be made without needing to fully excavate nests. This provides useful information to pest control experts and researchers studying yellow jacket colony dynamics. Understanding typical worker population sizes provides insights into the growth and development of these intricately organized social insect colonies.