common in Ohio
Baldfaced Hornet (Dolichovespula maculata) nests are now large enough to become noticeable. The same is true with Yellowjackets (Vespula spp. and Dolichovespula spp.) and Paper Wasps (Polistes spp.). These members of the wasp family, Vespidae, share common lifestyles and life cycles. Gaining an understanding helps avoid stinging encounters.
The wasps have been with us since the beginning of the season. However, they truly reveal themselves during the dog days of summer when an ever-increasing number of workers labor to expand nests at an exponential rate.
All three construct nests made of a paper-like material, although only one has “paper” in its common name. They use their powerful mandibles to scrape weathered wood and other plant fibers, then they mix the fibers with saliva to extrude a paper-like pulp. It’s common to see wasp wood scrapings on weathered fencing or barn siding, as shown in the image below.
The image below is a close-up of the fibers used in a baldfaced hornet nest. The wasp’s saliva contains various proteins and oils acquired from their victims, but more on that later. The proteins act as binding agents and the oils repel water. Each band represents a contribution made by a single worker. The fibers vary in their color, size, and arrangement based on the source material.
Baldfaced hornets most commonly harvest gray, weathered wood, which produces gray-colored nests. However, they occasionally scrape wood that’s been stained, and the resulting nest can be very colorful, as shown below.
Baldfaced hornet nests consist of two structural components. Horizontal combs, comprised of hexagonal brood cells, are stacked layer cake-like and supported by vertical elements that provide spacing and stabilize the entire structure.
Although the nests can appear in various shapes, they are usually top-shaped; larger at the top than at the bottom. This reflects the decreasing diameters of the brood combs with the largest at the top and smallest at the bottom.
The second part of the nest structure is the outside envelope. Note in the image below that it is multi-layered, which enhances insulation and protection against the elements.
Yellowjackets construct paper nests that are structurally similar to baldfaced hornet nests. However, the nests are hidden below ground or in attics, behind walls, or in other structural voids.
Paper wasp nests consist of exposed brood combs. They are never enveloped by a paper structure. The nests are located in protected locations such as under roof eaves, or even inside open buildings.
European Paper Wasps (P. dominula) nests are an exception. These non-native wasps carry the same black and yellow color motif of yellowjackets. They commonly build nests in locations that are not shared by our native wasps, such as in shrubs. The unexpected location presents a higher risk of stings compared to our native paper wasps.
Life Cycles
Baldfaced hornets, yellowjackets, and paper wasps begin and end the season the same way. Overwintered, mated females (queens) begin nest construction in the spring. Nests expand as more workers are produced throughout the summer. The workers are sterile females, which is why they possess ovipositors (ovi = egg) modified into stingers.
New queens and males (drones) are produced in the fall. Once they mate, the queens fly away to seek protected winter quarters. Eventually, the abandoned workers and old queen die owing to lack of food and freezing temperatures. It’s a sad end. Nests are never used for more than one season in Ohio.
The life cycles of baldfaced hornets, yellowjackets, and paper wasps are only slight variations on the same theme, with one exception. Paper wasp nests may be initiated in the spring by more than one queen, but eventually only one queen dominates, and the others become subordinates.
Note that the nascent baldfaced hornet nest pictured above is located beneath protective foliage. This isn’t by accident. The foliage provides shading and added protection against driving rainfall. The downside is illustrated in the images below. Baldfaced hornet nests that are camouflaged by foliage can be difficult to spot until close encounters solicit a stinging response.
Misunderstood Stingers
Baldfaced hornets, yellowjackets, and paper wasps exhibit behaviors that are a bit like Dr. Jekyll and Mr. Hyde, from our human perspective. On one hand, they are significant beneficial insects. They provide a twofer, serving as both predators and pollinators. On the other hand, they can appear monstrous by delivering painful stings.
They are Predators
The 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. The image below shows paper wasp larvae waiting to be fed, but the same arrangement also occurs in the nests of baldfaced hornets and yellowjackets.
Wasp meat items commonly include significant plant pests, as demonstrated in the image below. While taking pictures of a Box Tree Moth (Cydalima perspectalis) infestation in southwest Ohio, I observed numerous Eastern Yellowjackets (Vespula maculifrons) macerating the caterpillars. The carnage was widespread and significant in terms of the number of caterpillars being destroyed by the buzz squad.
The image below shows a bagworm (Thyridopteryx ephemeraeformis) bag that has been ripped open. The suspected assailant was a baldfaced hornet that extracted the caterpillar meat morsel inside. There were two baldfaced hornet nests located nearby.
They are Pollinators
Where do the wasp workers get carbohydrates for energy? One source is nectar from flowers. Wasps are not as hairy as bees, so they aren’t as efficient at carrying and distributing pollen. However, look closely at the image below of a northern paper wasp (P. fuscatus) working over goldenrod (Solidago sp.) flowers. The underside of the thorax looks “powder coated” with pollen.
The series of images below shows baldfaced hornets, yellowjackets, and paper wasps sipping nectar-fuel from flowers to power their search for meat items. Note the wide range of flowers visited by these wasps.
They are Belligerent Beneficials
Although these wasps are considered beneficial insects, they may be hard to appreciate while dealing with a painful, burning sting. But despite their belligerent reputations, the wasps 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.
However, these wasps will defend their nest at all costs, and they have the ability to sting multiple times without dying. Their stingers lack barbs, meaning they can jab and inject venom over and over again, presumably uttering, “Take That! And THAT!” in wasp-speak.
Safety by Avoidance
Accidental encounters can be mitigated by signage if the nest presents a perceived risk to the public. The signs below were used to alert the public of the possible hazard and to keep people a safe distance away from wasp nests.
In 2022, the Civic Garden Center of Greater Cincinnati used a two-pronged approach to keep people safe from baldfaced hornets while also providing an educational message. They used yellow caution tape to keep people outside of the “nest defense zone.” Baldfaced hornets will leave you alone if you remain outside of the zone, but attack if you get too close. They also posted an educational sign describing the behavior and value of the beneficial insects.
Thus far, I’ve never suffered an allergic response to wasp or bee venom. So, as a curious entomologist (a.k.a. foolhardy?), I decided to “test the zone” by crossing the tape to take a series of pictures as I inched closer to the nest. My camera and lens were on the same setting as I slowly approached the nest. Note the changes in defense behavior of the baldfaced hornet guards (and me!) as I crept closer.
The bottom line is that baldfaced hornets, yellowjackets, and paper wasps provide an ecological service that should supersede their negative reputation. Intentional encounters aimed at waging war on these well-armed wasps are high-risk endeavors.
We’re woefully outclassed because the 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. If possible, nests should be left alone to let nature take its course at the end of the growing season.
Where nests are perceived to present a risk, they should first be assessed to determine if they truly represent a clear and present danger, as illustrated in the images below. In this case, a well-positioned sign may be considered.
A Word of Caution!
Caution is the operative word if more drastic action is required. Some over-the-counter products shoot an insecticide stream an impressive distance. However, painful outcomes, accompanied by creative streams of expletives, can still result from applicator errors. Hiring a professional should be strongly considered, particularly when dealing with baldfaced hornets and yellowjackets.
NOTE: A special thanks to Lois Rose, Horticulture Maven, Master Gardener Extraordinaire, and Alert BYGL proofreader, for sending me a baldfaced hornet nest that appears in some of my images.
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), 445-458.
https://doi.org/10.1093/aesa/47.3.445
Curtis, T. R., Aponte, Y., & Stamp, N. E. (2005). Nest Paper Absorbency, Toughness, and Protein Concentration of a Native vs. an Invasive Social Wasp: Curtis et al. Journal of Chemical Ecology, 31(5), 1089-1100.
https://doi.org/10.1007/s10886-005-4249-x
Ertürk, Ö. (2017). Determination of some structural features of the nest paper materials of Dolichovespula saxonica Fabricius, 1793 (Hymenoptera: Vespinae) in Turkey. Entomological Research, 47(5), 286-294.
https://doi.org/10.1111/1748-5967.12208Digital Object Identifier (DOI)
Espelie, K. E., & Himmelsbach, D. S. (1990). Characterization of pedicel, paper, and larval silk from nest of Polistes annularis (L.). Journal of Chemical Ecology, 16(12), 3467-3477.
https://doi.org/10.1007/BF00982111
Jimenez, S. I., Gries, R., Zhai, H., Derstine, N., McCann, S., & Gries, G. (2016). Evidence for a nest defense pheromone in bald-faced hornets, Dolichovespula maculata, and identification of components. Journal of Chemical Ecology, 42(5), 414-424.
https://doi.org/10.1007/s10886-016-0699-6
Stein, K. J. (1990). A study of factors affecting queen survival, nest initiation, and nest development in the baldfaced hornet Dolichovespula maculata (L.) (Hymenoptera: Vespidae). [Doctoral dissertation, Virginia Tech]. ETDs: Virginia Tech Electronic Theses and Dissertations.