Hornets are social insect living in a colony of 100 to 400 members. They are of around 2.2 inches in size having 20 species in the world. They are usually active in summers and nest in trees, shrubs, houses, sheds or other structures. Their nest can be of 14 to 24 inches in diameter. Hornets are most aggressive members of wasp family. They tend to attack anyone trying to invade their territory. Some of the hornet species contains dangerous venom that can even cause death. Itchiness, swelling and irritation are common signs after hornet stings.