Exopterygota

Definition

A superorder of insects within the infraclass Neoptera characterized by incomplete metamorphosis (hemimetaboly), in which immature stages (nymphs) resemble adults and develop wing buds externally that become visible as sheathed structures on the thorax after early instars. Unlike Endopterygota, exopterygotes lack a pupal stage; adults emerge through a final moult after gradual nymphal development. Also called Hemimetabola.

Etymology

From Greek exo- (outside) + pterygo- (wing) + -ota (having), referring to the external development of wing rudiments in nymphs.

Example

Dragonflies (order Odonata) are exopterygotes: their aquatic nymphs bear paired wing pads on the thorax that enlarge through successive instars until the final moult to aerial adults.

Synonyms

• Hemimetabola

Related Terms

• Endopterygota
• Incomplete metamorphosis
• hemimetaboly
• nymph
• wing bud
• instar
• Pterygota
• Neoptera

Usage Notes

The term emphasizes developmental mode rather than phylogenetic relationship; some classifications treat Exopterygota as paraphyletic relative to Endopterygota. Wing buds are visible externally from mid-instar nymphs, contrasting with the internal, histoblast-derived wing discs of endopterygote larvae. Common orders include Orthoptera, Hemiptera, Mantodea, and Plecoptera. The synonym Hemimetabola is sometimes preferred to avoid implying a monophyletic superorder.