Beetles are the most diverse group of organisms on Earth. More than 350,000 species of beetle have been described, making one in every five species of organism a beetle. Beetles got an early start; the first beetles appeared during the Triassic (about 240 million years ago). Munching on plants, algae, and fungi, beetles were well-positioned to exploit the first flowering plants as they arrived on the scene. Beetles were among the first pollinators, visiting flowers to eat nectar and other plant products. Flowers became specialized for attracting (and feeding) beetles, such as magnolias whose appearance and smell continues to attract beetles. While bees certainly have the monopoly on pollination these days, the win-win relationship (mutualism) between beetles and flowering plants may have contributed to beetles becoming an exceptionally diverse group. Their sturdy body plan, with a hardened set of front wings (elytra) protecting the softer, hind wings underneath, may also have contributed to their success.

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.