Hemimetabolism

Hemimetabolism, also known as partial metamorphosis or paurometabolism, is a special way that some insects grow and change. These insects go through three main stages: the egg, the nymph, and the adult, which is also called the imago. Unlike some other insects, they do not have a pupal stage.

During their life, these insects change slowly. The nymph looks a bit like the adult but is smaller and does not have wings or working reproductive organs. As the nymph grows, it goes through several stages called instars, and each time it grows, it sheds its old skin in a process called moulting. The final stage, the adult, does not shed its skin anymore.

This way of developing helps these insects adapt to their environments and play important roles in nature, such as being part of food chains or helping with pollination.

Orders

All insects in the Pterygota except those in Holometabola go through hemimetabolism. This includes groups like Hemiptera (such as scale insects, aphids, whitefly, cicadas, leafhoppers, and true bugs), Orthoptera (grasshoppers, locusts, and crickets), Mantodea (praying mantises), Blattodea (cockroaches and termites), Dermaptera (earwigs), Odonata (dragonflies and damselflies), Phasmatodea (stick insects), Phthiraptera (sucking lice), Ephemeroptera (mayflies), Plecoptera (stoneflies), and Notoptera (icebugs and gladiators).

Terminology of aquatic entomology

In water bug studies, different words are used for insects that change slowly. Paurometabolism means the young bugs, called nymphs, live in the same place as the grown-ups, like some water striders. Hemimetabolous means the young bugs, called naiads, live in water, but the grown-ups live on land. This includes mayflies, stoneflies, and dragonflies. Scientists use these words to know if the grown-up bugs will live in water or on land.