damsel bug, (family Nabidae), any predacious insect in the true bug order, Heteroptera, that feeds on insect eggs, aphids, and small caterpillars. Damsel bugs are generally divided into two types. One is about 8 mm (0.3 inch) long and yellow-brown in colour with well-developed wings, and the second is larger, shiny black, and usually has very short wings.
Each foreleg of the damsel bug is slightly thickened and has a double row of spines that act as grasping organs when the leg bends. Nabis is one of the most common genera in this family, which contains about 300 species throughout the world.