The Carlisle Mosquito Online

Friday, September 26, 2003


Biodiversity Corner Bald-faced Hornet

photo by Ellen Huber
Name: Dolichovespula maculata or Bald-faced Hornet. Common names are troublesome things. This creature is not truly a hornet. Hornets are members of the genus, Vespa. Ground-nesting yellowjackets are members of the genus Vespula, and aerial-nesting yellowjackets like the bald-faced "hornet" are in the genus Dolichovespula. They are all in the family Vespidae, along with additional genera, and collectively referred to as vespids or wasps.

When and where found: Mid-September, a nest at the Red Balloon Nursery School on School Street · since removed · another in an apple tree at the Mosquito office on Westford Street; yet another attached to Janet Veves' deck on Rockland Road.

Distinguishing characteristics: About 3/4 inch long, largely black but with white markings on the face, the base of the wings, the waist and the tip of the abdomen. They are social insects living in colonies in a communal nest. The nests reach a foot or more in length, and are somewhat oval though wider at the top than the bottom. To say that the nests are built of paper made from chewed wood and saliva doesn't do justice to the color palette of gray, green and brown and the wavy patterns of stripes. The nests are attached to trees or buildings. Inside the nest are horizontal layers of hexagonal cells. The nests are easiest to spot in the fall because they are at their largest and not hidden by leaves. If you want to examine a nest, first read the next section about stings and then wait until we have had several weeks of frost.

photo by Kay Fairweather
Stings: The stinger is a modified egg-laying tube and so only the females are able to sting. Unlike the bee's barbed stinger, the bald-faced hornet's stinger has no barb and can easily be withdrawn and used to sting again and again. I once got a hornet inside the back of my shirt and neither of us was happy with the situation. The bald-faced hornet defends its nest very aggressively when threatened. Approaching too close can be interpreted as a threat, as Janet has discovered. There could be as many as 400 to 700 workers in a nest each capable of inflicting multiple stings.

Life Cycle: Only the fertilized queens survive the winter. They do not remain in the nest but find a protected crevice in a building or a tree trunk. In the spring, the queen builds a small nest with a few cells and lays an egg in each one. The larvae hatch from the eggs in about a week and are fed by the queen for 10 to 12 days after which time they pupate for another 12 days. During these first few weeks, the solitary queen is doing all the chores. When the sterile females emerge they go to work for the queen, extending the nest, bringing back food for the new larvae and defending the premises. The queen now has only to lay eggs. Later in the season, the queen lays eggs that will develop into fertile females and males which mate. The old queen dies, the worker behavior becomes erratic, and then except for the fertilized females which will start the next year's cycle, the rest of the colony dies.

What to do about a nest: Most of the advice I found suggested leaving nests in place if at all possible and giving them a wide berth. Mark out a zone around the nest as a reminder to yourself and a warning to others. If the nest is in an inconvenient place (or in a nursery school) and needs to be removed, it is best to call a professional. Even though the nest is quiet at night and relatively inactive, any disturbance is an alarm that puts all the workers on alert.

References: Donald W Stokes, A Guide to Observing Insect Lives;;

Any kind of information for the Biodiversity Corner is encouraged. Please feel free to write the column, or tell me what you are finding, or send me a photo. The only requirements are that the subject exists in the wild and was seen in Carlisle. Send a note to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to

2003 The Carlisle Mosquito