Bald-faced Hornet
| Scientific Name | Dolichovespula maculata |
| Survival Strategy | Annual Colony /Freeze-Tolerance (queen only) |
| Conservation status | Least Concern |
Spring
The female bald-faced hornet emerges from quiescence (think hibernation in insects) and begins building a new nest. Acting as a solitary wasp, the queen deposits eggs, forages for food, feeds her larvae, and increases the size of the nest.
Summer
The first eggs the queen lays will produce female workers. The role of these workers is to hunt for prey, feed larvae, and enlarge the nest. The queen continues laying up to 400 eggs and feeding larvae. Offspring born in mid-summer have the ability to reproduce. The females are potential queens for next year’s new colonies. In late summer, the reproductive females and males leave the nest. The queen dies, and the short-lived workers are not replaced. The nest is soon empty.
Fall
The sub-freezing temperatures of fall will kill off any remaining workers. Wasps will never use the nest again. After mating, females will store sperm until needed the following spring. The male bald-face hornets die, and the future-queen females seek a sheltered location.
Winter
Future-queen bald-faced hornets spend the winter alone, in a state of quiescence. They are the last living members of the colony.
Behavior
Nest Building
The construction of the aerial wasp nest begins almost immediately after the queen becomes active in the spring. She builds the nest from wood and other plant fibers that the wasp chews into a pulp with the help of saliva. This behavior is said to have inspired the invention of paper in China in the year 105.
Nest building never stops until the colony declines. The initial nest may be as small as a gulf ball, but as the number of workers increases, the nest can grow to the size of a basketball.
Nest Defense/Aggressive Behaviors
The bald-faced hornets can spray venom from their stingers into the eyes of nest intruders, causing temporary blindness. They can sting multiple times because their stingers are not barbed. The sting from these wasps contains venom and releases alarm pheromones that help additional defenders quickly locate and attack an intruder.
Physiology
Metamorphosis
Bald-faced hornets undergo complete metamorphosis. People rarely see the egg, larva, and pupa stages because their development occurs in the nest’s hexagonal cells.
Temperature Regulation
Bald-faced hornets regulate the temperature in their thorax, producing heat through muscle contractions. This extra heat allows them to be active at cooler temperatures and gives them a competitive advantage while pursuing prey or defending their nests.
Freeze Tolerant Queens
Overwintering future-queens are freeze tolerant. To prevent cell damage (and death) from ice, they produce a chemical (ice-nucleating protein) in the fluid between their cells that trigger ice crystals to form slowly and stay small. The slow formation of ice reduces the pressure differences on either side of the cell membrane, so the ice will only do minor damage. They also produce glycerol, an antifreeze protein that lowers the freezing point of the wasp’s blood (hemolymph) and the fluids inside the cells. This protection from the cold is similar to how woolly bear caterpillars survive the cold of winter.
Diet
Bald-faced hornets are omnivores. Their diet is primarily insects, including other yellowjackets. They also feed on plant pollen, nectar, and fruits.
Yellowjackets are beneficial insects. By preying on garden pests and serving as essential pollinators, they have earned the respect of many gardeners. Less endearing is their preference for sugary liquids, particularly in open soda cans at a picnic.
Lifespan and Mortality
The lifespan of a bald-face hornet ranges from 12 to 22 days for males and up to one year for queens.
Predators
As fierce as the bald-faced hornet is, it still has a wide range of predators. Larvae are rich in protein and are eaten by mice, raccoons, and foxes. Adult wasps are eaten by birds, spiders, frogs, and dragonflies.
Climate Vulnerability
Medical records in Alaska show an increase in patients seeking medical care for insect bites and stings, which may be related to the area experiencing a winter temperature increase of more than 3.3°C (6°F) since 1950.
As the climate becomes warmer, there may be an increase in “super nests” that do not die out over the winter and have multiple queens producing eggs. Wasp nests the size of a small car are possible.
Never stop learning
The Case for Scientific Names
Bald-faced hornets are not hornets. They are yellowjackets, a type of wasp, and are often called bald-faced aerial yellowjackets. To add to the confusion, they are not yellow. With at least 16 different common names, it is easy to see why biologists worldwide use the same two-part scientific name: Dolichovespula maculate
References
| A generic key to the nests of hornets, yellowjackets, and paper wasps worldwide (Vespidae, Vespinae, Polistinae). American Museum novitates; no. 3224 Wenzel, John W. http://hdl.handle.net/2246/3502 |
| Hunt, James H., and Toth, Amy L., “Sociality in Wasps” (2017). Ecology, Evolution and Organismal Biology Publications. 273. https://lib.dr.iastate.edu/eeob_ag_pubs/273 |
| “Bald-faced Hornets | Horticulture and Home Pest News” https://hortnews.extension.iastate.edu/bald-faced-hornets |
| Wasps Use Wood to Construct Paper Homes https://www.thoughtco.com/how-wasps-build-wasp-nests-1968103 |
| Demain, Jeffrey & Gessner, Bradford & McLaughlin, Joseph & Sikes, Derek & Foote, J. (2009). Increasing Insect Reactions in Alaska: Is this Related to Changing Climate?. Allergy and asthma proceedings: the official journal of regional and state allergy societies. 30. 238-43. 10.2500/aap.2009.30.3231. https://www.researchgate.net/publication/26313889_Increasing_Insect_Reactions_in_Alaska_Is_this_Related_to_Changing_Climate |
| What is the Difference Between Bees, Wasps, and Hornets? https://youtu.be/KDGJmzqvKTg |
| Bernd Heinrich, Summer World: A Season of Bounty – Chapter 5. Bald-Faced Hornet Nests (2009) https://publicism.info/environment/summer/6.html |
| Pensoft Publishers. “Call for arms and stings: Social wasps use alarm pheromones to coordinate their attacks.” ScienceDaily. ScienceDaily, 2 December 2015. www.sciencedaily.com/releases/2015/12/151202124556.htm. |
| Duman, J. G., & Patterson, J. L. (1978). The role of ice nucleators in the frost tolerance of overwintering queens of the bald-faced hornet. Comparative Biochemistry and Physiology — Part A: Physiology, 59(1), 69-72. https://doi.org/10.1016/0300-9629(78)90308-0 |