Phasmids are named for their excellent camouflage that makes them almost impossible to see in the wild (Phasmida = "apparition"). Living in temperate and tropical areas all over the world, they are adapted to mimic, or look like twigs or leaves , vanishing into the vegetation. Stick insects are long and brown with bumpy surfaces like bark, while leaf insects are green and flat with ridges like leaf veins. Phasmid behavior supports their camouflage, as they freeze in place or sway from side to side like a leaf in the breeze. Despite their uncanny ability to blend in, phasmids have other defenses at their disposal. Some release noxious chemicals that stink or burn. Some phasmids fall out of trees and play dead. A few species take an opposite approach, making loud sounds and flashing bright colors to startle predators. Phasmids are usually active at night (nocturnal), using their keen eyesight to get around when daytime predators are asleep.

Insects are by far the most diverse and abundant group of organisms on Earth. More than one million insect species have been identified, and estimates of how many species exist range into the tens of millions. Insects got their start way back, in the Paleozoic (about 500 million years ago) and have evolved in tandem with flowers (coevolution). Insects have become specialized on particular flowers, leading to complex sets of adaptations that couple them in a feeding and pollination relationship (a mutualism). Specialization allows for many types of insects to live in the same habitat, accommodating their exceptional biodiversity. In a backyard in the temperate zone, one might find several thousand species of insects. Specialization can occur within one plant species as well, with different insects using different parts of the plant. In just one species of tropical tree, Dr. Terry Erwin of Smithsonian's National Museum of Natural History found about a thousand species of beetles.