Careful!

Bald-faced Hornet feeding on plum
Bald-faced Hornet (Dolichovespula maculata) feeding on a rotting plum.

 

Bald-faced hornets (Dolichovespula maculata) are a common sight around here most years. This year, however, hornets were hard to find. Very few nests were started and the several I did see were soon abandoned. Finding these hornets in late September examining and feeding on rotting plums left on the porch was a good sight.

Bald-faced hornets build huge paper nests in trees and under the eaves of buildings. The nests are colonies consisting of one queen (sometimes two), who lays eggs, and many workers who tend the eggs and larva in their nest cells, hunt for food, enlarge the nest, and defend the colony from predators. The grub-like larvae eat macerated insects that the workers bring back to the nest. Barn flies seem to be a favorite prey at my place. Hornets also eat sweet foods like fruit and nectar and will scavenge from animal carcasses.

Description
Bald-faced hornets are yellow jackets but unlike yellow jackets their bodies are black with white markings. The face is marked with a white area between the eyes that extends to the jaws giving them the common name “bald-face hornet”. The large compound eyes are framed by white bands. There are white linear and triangular markings on the sides of the thorax and three white bands on the last three dorsal abdominal segments. The rest of the body is black. Wings are a translucent smokey brown. Overall body size is about 75 millimeters. Worker caste hornets are covered with fine hairs but the queens are hairless.

The syrphid fly Spilomyia fusca is a bald-faced hornet mimic.

Life Cycle
Nests are begun in the spring by fertile queen hornets that have overwintered. A small nest is started and the queen lays eggs in hexagonal paper cells. In about one week the eggs hatch into larva. The queen feeds these larva and after eight days the larva pupate. It takes another ten days for the pupating larva to develop into adults of the worker caste.

 

Hornet nest in a tree
Hornet nest on a tree branch showing entrance and cupolas.

 

The new workers begin the next stage of stage in nest development enlarging the nest and raising the young. The queen now devotes her time fully to egg laying. The queen lays eggs that will become diploid sterile females and sterile males. As more workers are produced the colony grows and can have as many as 700 hornets but usually there are around 400. The nest is enlarged with additional layers of brood cells enclosed in a paper cover. The paper is made from wood fibers the hornets collect from dried plant stems, bark, trees, and even paper. The fibers are chewed and mixed with saliva to make a sort of papier-mâché. Because they use so many fiber sources the nest will have dark and light patches of gray, white, brown, and yellow. The shape of the nest is initially rounded but later becomes conical with the narrow end at the bottom where there is an opening for the hornets to enter and exit. The outer paper cover is also layered and fitted with cupolas near the top. Most nests are about a foot across and two feet long but I have found some as long as three feet.

In late summer the reproductive phase of the colony’s life begins. Bald-faced hornet workers are female and can lay eggs. However, the eggs are not diploid but haploid (half the chromosome compliment) and become males which are fertile. These males will mate with the fertile females the queen produces at this phase.

After mating the colony begins to dwindle and work on the nest stops. There may be infighting among the workers and against the queen. Newly mated queens will leave the colony and prepare for winter hibernation to wait until spring when they will start new colonies of their own.

 

 

Taxonomy
Class: Insecta (Insects)
Order: Hymenoptera (Ants, Bees, Wasps and Sawflies)
Superfamily: Vespoidea (Yellowjackets and Hornets, Paper Wasps; Potter, Mason and Pollen Wasps and allies)
Family: Vespidae (Yellowjackets and Hornets, Paper Wasps; Potter, Mason and Pollen Wasps)
Subfamily: Vespinae (Hornets and Yellowjackets)
Genus/species: Dolichovespula maculata

Habitat
Bald-faced hornets live in a variety of habitats from forests to suburban areas. They prefer to build their nests in trees often

Range and distribution
Bald-faced hornets occur from Alaska east to Labrador south to Florida, Louisiana, and California but are not known from the Plains States and desert regions of the US.

Beware of Stings
The sting of bald-faced hornet is extremely painful and can cause allergic reactions in susceptible people. The old adage about stirring up a hornets nest is a good one to heed. But when the potential danger is respected hornets can make good neighbors and their appetite for insects makes them helpful in the garden.

References consulted
Archer, M. E. (2006). Taxonomy, distribution and nesting biology of species of the genus Dolichovespula (Hymenoptera, Vespidae). Entomological Science 9: 281-293.

Balduf, W. V. (1954). Observations on the White-faced Wasp Dolichovespula maculata (Linn) (Vespidae, Hymenoptera). Annals Entomological Society of America 47:445-458.

Bug Guide Species Dolichovespula maculata – Bald-faced Hornet

Hicks, B. and Baker, K. (2014). The nests of Dolichovespula norvegicoides (Hymenoptera: Vespidae) from Newfoundland. Journal of the Acadian Entomological Society 10:6-9.

14 thoughts on “Careful!

    1. There’s a large European hornet/wasp that is supposed to be very aggressive. It’s been in the US for almost a century now mostly on the eastern coast. Lately it has started moving west. I remember them and their nests on our house when I was younger. They were mean looking.

      Like

  1. These guys are bad ass. I’ve enjoyed watching them pick off flies and other insects while I’m milking the cow. They come in grab they prey and are awesome. Had to light one nest on fire where it hung at the end of a gate and disturbed them when the gate was opened. Burning worked well. I lit some paper on the end of a long bamboo pole and it went up in flame quickly lit at the bottom. Otherwise, I leave the nests and they don’t bother me at all. Had to drive a lawn tractor directly 1′ under one all summer one year where it hung in a maple and had not problem with them whatsoever.

    Liked by 1 person

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s