Earwig mothers make an unusual investment in their offspring, at least in the few species that have been studied to date. Parental care has been found in a both a primitive earwig and an advanced one, suggesting it might occur in most species. In dark, damp refuges, such as under bark or stones, female earwigs either lay eggs or give birth to live young. Egg-laying (oviparous) earwigs may tend the eggs by cleaning them, removing fungi, and warding off predators. After they hatch in a week, young earwigs still benefit from the mother's attention. She regurgitates her meals or may guide them to decayed matter. They stay with her and shelter under her larger body. About halfway through their development, after a couple of months, earwigs graduate from her care. They use the forcep-like structures (cerci) that have developed on their abdomens to capture their own food and defend themselves.

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.