Insects (Insecta) are a class of joint-legged (Arthropoda). With almost a million species, it is by far the largest group of animals. Estimations are many hunderd thousands or millions of species aren't even discovered yet. The name insect refers to the main characteristic of the whole group, the body that is divided in three parts.
Insects live on the land and in fresh water, only a few species live in the sea, but here Crustaceans (another class in the group of joint-legged) take the place of insects.
