Which statement best contrasts the exite-limb hypothesis with the tergite hypothesis for insect flight evolution?

• A. Exite-limb: wings from thoracic expansion; Tergite: wings from gill-like structures.
• B. Exite-limb: wings from gill-like structures; Tergite: wings from thoracic expansion.
• C. Exite-limb: wings from abdominal plates; Tergite: wings from leg segments.
• D. Exite-limb and tergite describe identical origins.

Answer: (B)

Two main ideas explain how insect wings might have evolved. The exite-limb idea argues wings came from exites—gill-like lateral outgrowths on legs that in early aquatic relatives might have functioned like gills, later flattening and becoming wings. The tergite hypothesis, on the other hand, says wings originated from expansions of the dorsal thoracic plates (tergites), essentially paranotal lobe-like surfaces that grew outward to form flight surfaces, not from limb tissue.

The statement that pairs exite-limb with wings from gill-like structures and tergite with wings from thoracic expansion captures exactly this contrast: one origin linked to limb outgrowths (exites) and the other to dorsal thoracic plate expansions (tergites). The other formulations mix these ideas or assign origins to different body parts, which isn’t what these two hypotheses propose.