This species is a yellow jacket wasp, not a true hornet. Colonies contain 400 to 700 workers. It builds a characteristic large hanging paper nest up to (23 in) in length. Workers aggressively defend their nests by repeatedly stinging invaders. Nests are layered hexagonal combs covered by a mottled gray paper envelope. Bald-Faced Hornets create this paper envelope by collecting and chewing naturally occurring fibers. The wood fiber mixes with their saliva to become a pulpy substance that they can then form into place. Bald-faced hornets are omnivorous and are considered to be beneficial due to their predation of flies, caterpillars, and spiders. However, their aggressively defensive nature makes them a threat to humans who wander too close to a nest or when a nest is constructed too close to human habitation. They vigorously defend the nest, with workers stinging repeatedly, as is common among social bees and wasps. However, the baldfaced hornet has a unique defense in that it can squirt venom from the stinger into the eyes of nest intruders. The venom causes immediate watering of the eyes and temporary blindness.