Specialized prey-trapping predation and phragmosis in a Cretaceous beetle larva.

We find a specialized Pachyteles-like larva from mid-Cretaceous Kachin amber, which represents a rare insight into the behavioral and morphological adaptations of early beetles. In our finding, its terminal disk morphology suggests a highly specialized ambush predation strategy, integrating both prey capture and phragmotic defense-traits that were already well developed over 99 million years ago. This fossil not only reveals the antiquity of complex larval predation and defense behaviors in Carabidae but also pushes back the evolutionary origin of phragmosis among insects. It also allows for a functional morphological interpretation of ecological interactions in Cretaceous terrestrial ecosystems. This functional approaches offer a valuable lens for decoding the ecological complexity of Mesozoic food webs, revealing that intricate predator-prey relationships were already well established in the mid-Cretaceous.