Bald-faced hornets are social stinging insects that are a close relative to yellowjackets. The surface of their upper-midsection almost looks triangular from the side, and they have white markings on their face. They build paper nests at least three or more feet off of the ground, usually in trees, shrubs, on overhangs, houses or other structures. These nests can be as large as 14 inches in diameter, more than 24 inches in length and are grey, paper-like and enclosed. At their peak, their colonies may contain between 100 to 400 members.
One very important fact that you must know about bald-faced hornets is that they are EXTREMELY aggressive and will not hesitate to sting anything that invades their space. Their stings carry venom that makes the stings hurt, itch and swell for about 24 hours. Humans are at the same risk of allergic reactions from bald-faced hornet stings as with other insect stings. What makes them even scarier is they have smooth stingers, which means they can sting over and over again, can actually sense vibrations in the air, and remember their invaders face!
Although bald-faced hornets usually appear in late summer, if the weather stays at a constant warm temperature for a number of days, they can appear as early as mid-April.