Bald-faced hornets are primarily diurnal, meaning their activity cycle is restricted to daylight hours. This social wasp, which is technically a species of yellowjacket, relies heavily on sunlight for foraging and navigation. After sunset, the entire colony resides within its paper nest, entering a period of dormancy until dawn. This pattern is consistent with most social wasps in North America, but exceptions exist, particularly when the nest is threatened.
Diurnal Activity and Foraging Habits
The bald-faced hornet’s daytime activity is driven by the colony’s need for protein and carbohydrates, making them highly active from sunup to sundown. Worker wasps spend their daylight hours searching for food to sustain themselves and the developing brood inside the nest. Their primary role is that of a predator, focusing on soft-bodied insects like caterpillars and flies, which they chew up and feed to the larvae as a protein source.
Adult wasps also require quick energy, which they obtain by scavenging for sugary substances such as nectar, tree sap, and sometimes even other insects. Their reliance on visual cues for navigation and hunting makes them strictly diurnal, as they cannot effectively forage or locate their nest entrance in the dark. The peak of this activity is typically during the warm, sunny parts of the late summer when the colony reaches its maximum size.
What Happens After Dark
After the sun sets, the vast majority of the bald-faced hornet workers retreat into the nest, sealing the entrance and entering a quiescent state to conserve energy. This period of rest is the normal behavior for the colony and is why pest control professionals often recommend treating a nest at night.
A notable exception to their nighttime inactivity is their attraction to strong light sources, such as porch or security lights, which can disrupt their normal resting cycle. The brightness and heat from these lights can confuse the wasps, causing them to hover and sometimes forage around the light fixture, an unnatural behavior for a diurnal insect.
The most serious exception to their nightly rest is their immediate and forceful defensive response to physical disturbance of the nest. If the nest is struck or threatened after dark, the wasps will emerge en masse to defend the colony, stinging any perceived threat repeatedly. They release alarm pheromones when disturbed, which mobilizes the entire colony to attack. This defensive reaction is independent of light, demonstrating that the danger remains if the nest is approached or disturbed.
Identifying Bald-Faced Hornets and Their Nests
The bald-faced hornet is distinct from other wasps due to its unique coloration, which is primarily black with ivory or white markings on its face and abdomen. This black and white pattern makes them one of the most recognizable social wasps in North America. Their bodies are relatively large for a yellowjacket, contributing to their intimidating appearance.
The nest structure is the most definitive characteristic of the species, as they construct large, enclosed, football-shaped structures made of paper-mâché. Worker wasps create this paper by chewing wood fibers and mixing them with saliva, resulting in a gray, layered covering. These nests are typically aerial, often found high up in trees, attached to utility poles, or sometimes sheltered beneath the eaves of buildings. A mature nest in late summer can reach up to two feet in length, with a single entry hole near the bottom.