Flexible Drinking Straws of the Cretaceous: A Novel Type of Labium in Mesozoic Auchenorrhyncha and Its Functional Implications.

The evolution of novel feeding structures played a major role in the diversification of Hemiptera. Here, we investigate the morphology and inferred function of a highly specialized labium in the extinct Cretaceous planthopper families Neazoniidae and Mimarachnidae. These insects possessed a feeding apparatus unparalleled among extant Hemiptera that is characterized by an extremely elongated labium with a densely corrugated apical segment formed by sinusoidal cuticular folds. Comparative analysis, aided by micro-computed tomography, indicates that the cuticular corrugations were a mechanical adaptation that increased the flexibility of the tubular feeding structure while resisting kinking and buckling. We propose that this morphology facilitated probing within deep bark fissures and other mechanically resistant plant tissues, potentially enabling access to the vascular bundles. Similar corrugated feeding structures convergently occur in several unrelated Cretaceous hemipterans as well as some long-proboscid Mecoptera, suggesting that extinct Mesozoic ecosystems supported feeding strategies absent in their modern relatives. Furthermore, we propose the synonymy of Mimarachnidae with Neazoniidae based on the shared possession of this specialized labium morphology, along with other morphological features, establishing the taxonomic connection between nymph and adult specimens. We also transfer the unplaced genus Spinonympha to the family Neazoniidae and describe a new species of the genus Cretodorus.