Aquatic and Land Animal Diversity

Aquatic and Land Arthropods

Why are insects considered the most successful group of animals?

With more than one million described species (and perhaps millions more not yet identified), class Insecta is the most successful group of animals on Earth. In the United States alone, about 91,000 different species have been described, with an estimated 73,000 species not yet described. In fact, the largest numbers of species in the U.S. fall into the four insect Orders: Coleoptera (beetles) at about 23,700; Diptera (flies) at about 19,600; Hymenoptera (ants, bees, wasps) at about 17,500; and Lepidoptera (moths and butterflies) at about 11,500.

More species of insects have been identified than of all other groups of animals combined. What insects lack in size, they make up for in sheer numbers. If we could weigh all the insects in the world, their weight would exceed that of all the remaining terrestrial animals. About 200 million insects are alive at any one time for each human. And why are they successful? Flight is one key to the great success of insects. An animal that can fly can escape many predators, find food and mates, and disperse to new habitats much faster than an animal that must crawl about on the ground.


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