Larvae and adults feed on plants and on materials of plant origin. Eggs and pupae, of course, do not feed. The developmental time from egg to adult is variable from species to species. Some species have only one generation each year in the USA, whereas others have several generations, but with more generations in the hotter months than in the colder months. Most weevil species are innocuous because they have low populations and feed on plants of no particular consequence to humans.
Some species are beneficial because they feed on plants that humans consider to be weeds.
Some weevil species are highly beneficial because they have been used in biological control of important weeds.