Yellowjackets (Vespula spp. and Dolichovespula spp.), Baldfaced Hornets (D. maculata), and Paper Wasps (Polistes spp.) all belong to the wasp family, Vespidae. So, entomologists collectively refer to them as “wasps.”
Wasps share many traits including using their powerful mandibles to scrap weathered wood and then mix the fibers with saliva to extrude a paper mache-like material used to build their nests. It’s common to see wasp wood scrapings on weathered fencing or barn siding.
Wasps most commonly harvest gray, weathered wood which produces gray-colored nests. However, occasionally they will scrap wood that’s been stained, and the resulting nest can be very colorful.
Wasps will defend their nest at all costs and they have the ability to sting multiple times without dying. Their stingers, which are modified ovipositors (ovi = egg), lack barbs meaning they can jab and inject venom over and over again. Indeed, nest defense and multiple stings can be painfully connected.
Yellowjackets and baldfaced enclose their comb of hexagonal brood cells inside a paper envelope. Baldfaced hornet nests may be found in trees or shrubs with branches incorporated into their nests, or they may attach their nests to the sides of structures. Yellowjackets sometimes build nests inside shrubs, but usually may build inside structures or below ground taking advantage of a void dug by an animal.
Paper wasps construct their brood cells out in the open anchored against gravity by a single point called a pedicel. Their nests are protected from the weather by being located under roof overhangs, or inside open structures such as attics and outbuildings. They are easy to spot as long as you look up!
Wasp nests have been with us in Ohio since the beginning of the growing season. However, the wasps typically don’t appear on our radar until late summer to early fall when the colonies reach their zenith at the same time the wasps change their diet from meat to potatoes. But more on that later.
This year, Extension offices are already receiving complaints about wasps; particularly yellowjackets. It appears that yellowjacket populations are running high thus far this season producing stinging commentaries about close encounters.
Misunderstood Stingers
These wasps are significant beneficial insects although they may be hard to appreciate while dealing with a painful, burning sting. Yellowjackets, baldfaced hornets, and paper wasps are pollinators as well as predators: they provide a twofer.
Wasps are significant predators owing to their need to provide protein to the legless, helpless larvae awaiting food delivery in their nests. The wasp workers forage for caterpillars, sawfly larvae, and other soft-bodied insects from late spring through the summer. They use their powerful mandibles to grind up these protein-rich meat items to feed to their larvae so they will develop into new adults.
Wasp meat items commonly include significant plant pests. This was dramatically illustrated during a recent visit to a Box Tree Moth (Cydalima perspectalis) infestation in southwest Ohio. We observed numerous Eastern Yellowjackets (Vespula maculifrons) macerating box tree moth caterpillars. The carnage was widespread and significant in terms of the number of caterpillars being destroyed by the buzz squad.
Several years ago, I came across a native Northern Paper Wasp (Polistes fuscatus) converting a Catalpa Hornworm (Ceratomia catalpae) into a “meatball” to take back to its nest. Unfortunately, the hornworm was also covered with the cocoons of the parasitoid wasp, Cotisia congregata.
The image below shows a bagworm (Thyridopteryx ephemeraeformis) bag that was ripped open. The suspected perpetrator was a baldfaced hornet intent on extracting the caterpillar meat morsel inside. There were two baldfaced hornet nests located nearby.
Wasps are also pollinators. Paper wasps, baldfaced hornets, and occasionally yellowjackets will visit flowers to feed on energy-rich nectar to support their predatory foraging and wood fiber gathering flights. "Pollinator gardens” (a.k.a. butterfly gardens) are a rich location for photographing these wasps. They also ramp up their floral visits when their nest needs shift from high protein to high carbohydrates.
Belligerent Beneficials
Unfortunately, yellowjackets and baldfaced hornets have a deserved reputation for becoming serious nuisance pests late in the season. Once the male drones and new queens complete their development in late summer to early fall, the focus of the colony's workers shifts from gathering protein to support the growth of immatures to acquiring carbohydrates to meet the energy needs of adults.
The royal newcomers lounge around the nest begging the workers for sweets. To appease these freeloaders, the workers search for foods that provide an energy boost such as soda, donuts, funnel cakes, and adult alcoholic beverages. There are few things scarier than being chased by drunken belligerent baldfaced hornets decked out in their black leather jackets.
Another form of nuisance behavior is seen when these wasps visit hummingbird feeders. Although hummingbirds are highly aggressive in protecting their sugar source, they are occasionally driven off by interloping stingers.
Yellowjackets, baldfaced Hornets, and paper wasps will also seek a sweet treat in the form of honeydew exuded by plant-sucking insects such as aphids and soft scales. You may find these stingers on wasp galls where they serve as a security detail against gall predators in return for nectar exuded by extrafloral nectaries.
Yellowjacket traps are sometimes deployed to reduce the number of stingers arriving to spoil a picnic or drive customers from food trucks. However, research has shown that trapping can be problematic with careful positioning required to avoid enhancing rather than reducing a yellowjacket challenge. Even then, traps may not overcome the allure of rows of county fair concession stands offering scrumptious goodies best consumed after, but not before, a cholesterol test.
The most effective approach to managing yellowjackets and baldfaced hornets intent on crashing picnics, county fairs, and other outdoor gatherings is to remain diligent with trash collection. Overflowing trash cans is like a flashing neon “eat here” sign to these wasps.
Safety by Avoidance
Wasps spend the winter as fertilized females (queens) in protected locations such as beneath bark, inside hollow trees, etc. As spring temperatures warm, the queens leave their overwintering quarters to find suitable sites for nest construction.
The overwintered queens use their powerful mandibles to grind up fibers gathered from dead wood and plant stems which they mix with their saliva to extrude water-resistant paper used to construct their nests. This construction technique continues to be used by the queen’s offspring throughout the spring and summer.
Early wasp nests are relatively tiny structures. The elongated nests created by a baldfaced hornet queen may measure no more than 1 1/2" long. She gets help as her offspring complete their development which takes around 20 – 25 days in the Midwest.
This single dominant queen receives even more help once subordinate queens develop. Collectively, they lay more eggs which leads to more workers leading to larger nests that lead to more eggs … etc., etc. By mid-to-late August, the nests become large enough to be noticed, or not; sometimes painfully.
However, even the largest wasp nests are only used for only one season. Eventually, the nests give rise to new queens and males (drones). Once the new queens are mated, they fly to their overwintering sites leaving the workers behind to meet their freezing fate.
Despite their belligerent reputations, paper wasps, yellowjackets, and baldfaced hornets are seldom aggressive away from their nests. There’s simply no benefit in wasting energy chasing after people far from the wasp’s home base.
Of course, nest defense is a different matter. Painful meetings between these wasps and people most commonly involve an accidental or deliberate incursion by a person into the “nest defense zone.”
Accidental encounters are particularly common with subterranean yellowjacket nests. Baldfaced hornet nests may also be hidden within plant foliage which also presents a risk. The same is true for European Paper Wasps (Polistes dominula). These non-natives will have their own BYGL Alert.
Intentional encounters aimed at waging war on the well-armed yellowjackets, baldfaced hornets, and paper wasps are a particularly high-risk endeavor sometimes launched with “watch this!” but ending in writhing pain. We're woefully outclassed because these wasps have been defending their nests for hundreds of thousands of years. They have excellent eyesight and are programmed by Nature to execute several effective defense-attack strategies.
Baldfaced hornet nests commonly include a “back door” used for ventilation. Of course, the second opening also means that while an attacker focuses on the front entrance, hornets stream out of the second exit to arrive with bad intentions. Paper wasps commonly power dive onto nest threats and yellowjackets will land and crawl into clothing to deliver their multiple, painful stings.
Nest avoidance is the best option to avoid stinging confrontations. I've taken pictures in several parks over the years of signs posted near an underground yellowjacket nest alerting the public of the yellow-and-black threat.
Last year, the Civic Garden Center of Greater Cincinnati used yellow caution tape to protect visitors from a baldfaced hornet nest. They also took the opportunity to provide an educational message by affixing a sign to the exclusion enclosure.
Of course, a sign isn’t needed to alert people of a large baldfaced hornet nest located next to a home entrance. Although yellowjackets, paper wasps, and baldfaced hornets provide significant environmental services, those services should not supersede human safety.
Personal safety should also be applied to nest elimination. Suffering a mass attack is not a good time for people to learn if they are allergic to wasp venom. A nest that threatens human safety should be eliminated by a professional.
Yellowjacket traps are sometimes deployed to reduce the number of stingers arriving to spoil a picnic or drive customers from food trucks. However, research has shown that trapping can be problematic with careful positioning required to avoid enhancing rather than reducing a yellowjacket challenge. Even then, traps may not overcome the allure of rows of county fair concession stands offering scrumptious goodies best consumed after, but not before, a cholesterol test.
The most effective approach to managing yellowjackets and baldfaced hornets intent on crashing picnics, county fairs, and other outdoor gatherings is to remain diligent with trash collection. Overflowing trash cans is like a flashing neon “eat here” sign to these wasps.
Selected References
Balduf, W.V., 1954. Observations on the white-faced wasp Dolichovespula maculata (Linn)(Vespidae, Hymenoptera). Annals of the Entomological Society of America, 47(3), pp.445-458.
Miller, C.D.F., 1961. Taxonomy and distribution of Nearctic Vespula. The Memoirs of the Entomological Society of Canada, 93(S22), pp.5-52.
Braband, L., M. Frye, J. Lampman, D. Marvin, and R. Parker. 2016. Yellowjacket Trapping Efficacy Trials, NYS IPM Program, 2014-2016.
Grissel, E.E., and T.R. Fasulo. 2013 (revised). Common name: yellowjackets and hornets, scientific name: Vespula and Dolichovespula spp. (Insecta: Hymenoptera: Vespidae). Featured Creatures, Entomology & Nematology. FDACS/DPI, EDIS, UF|IFAS. Publication Number: EENY-81
https://entnemdept.ufl.edu/creatures/urban/occas/hornet_yellowjacket.htm
Oliver, J.B., P.J. Landolt, N.N. Youssef, J.P. Basham, K.M. Vail, and K.M. Addesso. 2014. Trapping social wasps (Hymenoptera: Vespidae) in nurseries with acetic acid and isobutanol. Journal of Entomological Science, 49(4), pp.352-368.
