The: Insects

: Most have large eyes made of many tiny lenses, which are excellent at detecting motion. Major Roles in Nature

: Includes four stages—egg, larva (like a caterpillar), pupa (chrysalis), and adult (butterfly). The Insects

: A hard external shell made of chitin that protects their organs. Because this shell cannot grow, insects must periodically molt to increase in size. : Most have large eyes made of many

: The young, called nymphs, look like smaller, wingless versions of the adults and grow through a series of molts. Because this shell cannot grow, insects must periodically

: An ant can carry more than 50 times its own body weight.

are the most diverse and abundant group of animals on Earth, making up more than half of all living species. Often called "the little things that run the world," they are essential to the functioning of almost every terrestrial ecosystem, serving as pollinators, decomposers, and a primary food source for many other animals. Key Characteristics

: Scientists estimate there are roughly 1.4 billion insects for every human on Earth.