What type of insects are primarily included in the gradual metamorphosis group?

Gradual metamorphosis, also known as incomplete metamorphosis, is a type of developmental process in certain insects where the young resemble smaller versions of the adults and there are no distinct stages like a pupa. Instead, the development occurs through several nymph stages that gradually evolve into adult forms. This process is characteristic of insects such as termites and cockroaches, which go through these incremental changes over time.

Termites and cockroaches fit this description as their life cycles progress from egg to nymph and eventually to adult, with each nymph stage closely resembling the adult form. In contrast, butterflies, moths, and flies all undergo complete metamorphosis, which involves distinct life stages, including larval (caterpillar or maggot) and pupal stages, that are markedly different from the adult form.

Understanding the differences between types of metamorphosis is crucial in entomology, particularly when studying insect behavior, ecology, and pest control.