The evolution of these structures occurred in three distinct tracks: sponge-like labellum of flies and caddisflies, siphon structures in butterflies and moths, and glossa in wasps and bees.
These structures underwent significant transformations along three distinct lines: the sponge-like labellum found in flies and caddisflies, the siphon structures present in butterflies and moths, and the glossa seen in wasps and bees.