Centipedes are very dangerous, and their bite is extremely painful. Millipedes share the same habitat as centipedes, but they are mostly herbivorous, feeding on decaying vegetation in the leaf litter. Animals that feed on detritus are called detritivores . If we knew all the different insects on Earth, there could be as many as 30 million species. Insects evolved about 200 mya, with cockroaches and dragonflies among the first to appear.
Most insects have one or two pairs of wings.
They are the only invertebrates that fly. Most have compound eyes , and can communicate by sound and scent, using powerful chemical hormones called pheromones . These mouthparts are highly modified in various groups for chewing, sucking, and piercing. Insects undergo metamorphosis as they develop, changing from one form to another as they mature. The juvenile stages look like tiny versions of the adults.