ONTOGENETIC RECONSTRUCTION OF EXTINCT AQUATIC PREDACEOUS BEETLE LARVAE FROM THE EARLY CRETACEOUS JINJU KONSERVAT-LAGERSTATTE, SOUTH KOREA

Insects are one of the most successful groups of eukaryotic organisms, with the number of described extant species reaching nearly a million, representing nearly 90% of all living animal species. Insect life history plays an important role in their taxonomic richness and ecological success. For instance, the holometabola (insects with complete metamorphosis; e.g., beetles, flies, moths, wasps) accounts for over 80% of total described living insect species, and their success is significantly aided by the temporal partitioning of multiple ecological niches throughout their ontogeny. However, studying insect ontogeny involves field collections of a large sample size of conspecific individuals at different stages or rearing and tracking individuals in captivity, which cannot be easily done in paleoentomological research. Therefore, our understanding of the life history of insects in the fossil record is limited.

The Early Cretaceous (110-106 million years ago; early to middle Albian) Jinju Formation, South Korea, is best known for its exquisite preservation of vertebrate trackways, including dinosaurs, pterosaurs, crocodylomorph, lizards, an anuran, and a hopping mammal. The Jinju Konservat-Lagerstatte also preserves a diverse array of terrestrial and freshwater arthropods. Some taxa are represented by a large number of their freshwater larvae in various stages, therefore providing an opportunity to investigate the larval ontogeny of these fossil insects. In particular, aquatic beetle larvae of Coptoclava sp., belonging to the extinct hydroadephagan beetle family Coptoclavidae (Triassic to the Early Cretaceous), are examined. The specimens’ head capsule dimensions were measured to determine the number of larval instar number using Dyar’s rule. Combined with the macromorphological characters and inferences from their living relatives, a life history reconstruction of the four larval instars of Coptoclava sp. will be presented.