Practice question

Insect development modes include ametabolous, hemimetabolous and holometabolous strategies. Drosophila melanogaster exemplifies holometabolous complete metamorphosis where embryo hatches into worm-like larva with three instars dedicated to feeding and growth, lacking external adult structures. Adult primordia grow internally as imaginal discs during larval stages. At pupariation pulse of ecdysone triggers pupal metamorphosis with histolysis of larval tissues and eversion differentiation of imaginal discs into wings, legs, eyes, genitalia. This separation of growth and morphogenesis phases enables ecological specialization contrasting with hemimetabolous gradual nymphal transformation.