Description of Bald-faced Hornets
Bald-faced hornets, also known as “bald-faced aerial yellowjackets,” are a species in the yellowjacket family. Similar to honey bees and ants, these hornets live in colonies. The nest they construct is made of paper-like material created by mixing chewed wood fibers with saliva. This multilayered nest consists of three or four tiers of combs enclosed in a thick outer shell. Typically, bald-faced hornet nests are found in wooded areas, attached to tree branches, but they can also be found on shrubs, utility poles, or house siding.
Image: Baldfaced hornets nest.
Life Cycle of Bald-faced Hornets
Bald-faced hornets are large, black insects measuring about 7/8 of an inch long. They have white to cream-colored markings on the front of their heads and at the end of their abdomens. Like other wasps, bees, and ants, hornets go through a complete life cycle comprising four stages: egg, larva, pupa, and adult. The larva, a legless grub, is nurtured within cells inside the nest. Bald-faced hornets are beneficial predators, feeding on various insects, including filth flies and blowflies.
A colony of social wasps, including hornets, yellowjackets, and paper wasps, lasts only one year. Each year, a new nest is built from scratch, as the previous year’s nest cannot be reused. Only the queens can survive the winter. In April or May, each queen chooses a suitable location, constructs a small nest, and begins raising sterile daughter offspring. These workers take on the tasks of enlarging and maintaining the nest, foraging for food, and caring for the offspring while the queen focuses on egg production.
Initially, colony growth is slow, but it accelerates rapidly by mid-summer as successive broods of workers emerge. The peak worker population, at the end of summer, ranges from 100 to 400 hornets. In the fall, males and new queens are produced. They leave the nest to mate, while the fertilized queens hibernate. The workers, old queen, and males die from old age or freezing temperatures.
Damage Caused by Bald-faced Hornets
The size of a hornet’s nest and their reputation often alarm people. However, despite their intimidating appearance, hornets are not as aggressive as they may seem. Disturbing a nest or threatening an individual wasp can result in stings. Hornets are highly protective of their colony and will usually attack if someone approaches within 3 feet of the nest. If a nest is located in a high-traffic area, such as along paths or near doorways, control measures may be necessary to reduce the risk of being stung. Nests away from human activity should be left undisturbed.
Management of Bald-faced Hornets
Controlling bald-faced hornet colonies can be relatively straightforward by using an insecticide aerosol spray specifically designed for this purpose. These sprays come with a special nozzle and propellant system that can project a thin stream of insecticide up to 20 feet.
It is recommended to exterminate colonies at night when the workers are least active and the maximum number is present at the nest. Safety precautions should be taken, including wearing protective clothing such as a thick jacket, long pants tucked into socks, gloves, and a hat.
The first step is to spray into the entrance hole, followed by thoroughly wetting the nest. It is crucial not to remove the nest until all the hornets are dead. This process may take a day or two since some workers may not have been present at the nest during the treatment. Always follow the labeled directions on the insecticide.
If you are interested in preserving a hornets’ nest as a decoration or conversation piece, check out the online article, “Preserving and Displaying a Hornet’s Nest.”
Do you live in Iowa and need help identifying an insect?
The Iowa State University Plant & Insect Diagnostic Clinic can assist you in identifying insects, providing information on their diet, life cycle, and the best ways to manage them if they are pests. Visit DHPL Travels to access our website for current forms, fees, and instructions on preserving and mailing insects.
For residents outside of Iowa, please refrain from submitting samples to the Plant & Insect Diagnostic Clinic without contacting them first.