Hemimetabolism orhemimetaboly, also calledpartialmetamorphosis andpaurometabolism,[1] is the mode of development of certain insects that includes three distinct stages: theegg,nymph, and the adult stage, orimago. These groups go through gradual changes; there is nopupal stage. The nymph often has a thinexoskeleton and resembles the adult stage but lacks wings and functional reproductive organs.[2] The hemimetabolous insects differ fromametabolous taxa in that the one and only adultinstar undergoes no furthermoulting.[3]
.jpg)
All insects of thePterygota exceptHolometabola belong to hemimetabolous orders:
In aquaticentomology, different terminology is used when categorizing insects with gradual or partialmetamorphosis. Paurometabolism (gradual) refers to insects whosenymphs occupy the same environment as the adults, as in the familyGerridae ofHemiptera. The hemimetabolous (partial) insects are those whose nymphs, callednaiads, occupy aquatic habitats while the adults are terrestrial. This includes all members of the ordersPlecoptera,Ephemeroptera, andOdonata. Aquatic entomologists use this categorization because it specifies whether the adult will occupy an aquatic or semi aquatic habitat, or will be terrestrial.