The hemimetabolan development

Abstract Hemimetabolan metamorphosis is characterized by the morphophysiology of the juvenile stages, which is similar to that of the adult. It is the developmental mode of Palaeoptera, Polyneoptera, and Paraneoptera. In these groups, embryogenesis follows the short germ band development, blastokinesis is characteristically complex, and there are three embryonic cuticle depositions: EC1, EC2, and EC3. The postembryonic development goes through the nymphal period, until reaching the reproductively competent adult, which stops molting. In the transition from the final nymphal instar to the adult, the wings and the genitalia become completely formed. Although maintaining the similarity between nymphs and adults, the postembryonic development can be relatively different in different groups. In most polyneopterans and paraneopterans, the morphophysiology of nymphs and adults is very similar; thus the development is gradual. However, in the palaeopterans (and in the order Plecoptera, within the polyneopterans), the nymphs are aquatic, while the adult is terrestrial. Finally, the postembryonic development of some paraneopteran groups, such as the Psylloidea, Aleurodoidea, and Coccomorpha (Hemiptera Stenorrhyncha), as well as the order Thysanoptera, comprises a series of nymphal instars, followed by a number of quiescent stages, reminiscent of the holometabolan pupa, before reaching adulthood.