About 75% of the world’s animals are insects. They (1) _________ on Earth for over 400 million years, long before humans appeared. Insects have changed a lot and adapted to new climates in order to survive. Today, there are about one million different species of insects, and scientists are (2) _________ new ones daily. Insects have (3) _________ sizes and body forms. Most of them are very small, but they can grow as large as 30 cm. Among (4) _________ most common insects are flies, beetles, butterflies, moths and wasps. Insects live in every region of the world. They can survive in any type of climate, from tropical rainforests to icy polar regions, as long as they can find food. They can live in places (5) _________ other animals cannot survive; some even live in underground caves.