Hornets, Paper Wasps and Yellow jackets are dangerous, unpredictable and should be treated with respect. Paper wasps typically build their umbrella-shaped nests under eaves and ledges. Hornet nests resemble a large, inverted tear-drop shaped ball which typically is attached to a tree, bush or side of a building. Hornet nests may contain thousands of wasps which are extremely aggressive when disturbed. Yellow jackets are another dangerous wasp encountered around homes and buildings. Nests are often located underground in an old rodent burrow, beneath a landscape timber, or in a rock wall or wall of a building. Wasp, hornet and yellow jacket stings can be life-threatening to people allergic to the venom.