Final answer:
Immature stages of aquatic insects with hemimetabolous or incomplete metamorphosis are called nymphs. Unlike insects with complete metamorphosis, these nymphs resemble the adult form from the beginning. They develop wings and other adult characteristics through a series of molts.
Step-by-step explanation:
The immature stages of aquatic insects with hemimetabolous or incomplete metamorphosis, such as grasshoppers and crickets, are called nymphs. These nymphs resemble their adult forms but don't have wing yet. They go through several molts growing bigger each time and eventually develop wings during their final molt.
In contrast, aquatic insects that undergo complete metamorphosis, like beetles, butterflies, or flies, go through a larval stage that looks very different from their adult form. They undergo metamorphosis and rapidly transform from their larval form into their adult form in a process that is often strikingly different.
This distinction between hemimetabolous and holometabolous (complete metamorphosis) insects is crucial in understanding not only their life cycle stages but also the different ecological niches they can occupy due to differences in their physical form, diet, and habituation between juvenile and adult stages.
Learn more about Hemimetabolous Metamorphosis