Hemimetabolism or hemimetaboly, also called partial metamorphosis and paurometabolism,[McGavin, George C. Essential Entomology: An Order-by-Order Introduction. Oxford: Oxford University Press, 2001. pp. 20.] is the mode of development of certain insects that includes three distinct stages: the egg, nymph, and the adult stage, or imago. These groups go through gradual changes; there is no stage. The nymph often has a thin exoskeleton and resembles the adult stage but lacks wings and functional reproductive organs.
Orders
All insects of the
Pterygota except
Holometabola belong to hemimetabolous orders:
Terminology of aquatic entomology
In aquatic
entomology, different terminology is used when categorizing insects with gradual or partial metamorphosis. Paurometabolism (gradual) refers to insects whose nymphs occupy the same environment as the adults, as in the family
Gerridae of
Hemiptera. The hemimetabolous (partial) insects are those whose nymphs, called naiads, occupy aquatic habitats while the adults are terrestrial. This includes all members of the orders
Plecoptera,
Ephemeroptera, and
Odonata. Aquatic entomologists use this categorization because it specifies whether the adult will occupy an aquatic or semi aquatic habitat, or will be terrestrial.
See also
