True bugs are diverse, ranging from tiny lace bugs to large water boatman. Their diets are diverse as well, but all true bugs feed by piercing and sucking food. The beak-like mouthpart of a true bug is like a trough that folds back under its body. One channel of the trough sends saliva out to moisten food, while the other channel sucks liquid food in. Despite their similar feeding apparatuses, the diets of true bugs vary. Many feed on sap, sucking it out of leaves, flowers, stems, shoots, or roots. Others are predators, using sharp beaks to stab small prey such as snails. Parasitic true bugs, such as bed bugs, pierce the skin of mammals or birds and feed on their blood. More unusual diets include jellyfish or fungi from under tree bark. The piercing and sucking technique even allows some true bugs to liquefy and eat mosses or seeds.

Insects are the only animals without backbones (invertebrates) that can fly. Wings of insects are flat and paper-thin, supported by a network of veins. They flap their wings at incredible rates, up to about two hundred times per second. Most insects have two sets of wings that work in tandem because they are coupled by a fold, a hook, or other structure that catches the back wing as the front wing beats. Wings are made of two layers of cuticle for strength. The front wing is often hardened to serve as a protective cover, leaving the back wing to provide most of the flying power. Many insects walk around instead of, or in addition to, flying. The good walkers tend to touch three legs to the ground at a time, alternating with other sets of three (tripedal gait). The stable triangles formed by the legs allows them to move quickly without falling over. Some insects "walk" on water or swim.