Revisiting the larval morphology of Oiceoptoma thoracicum (Coleoptera: Staphylinidae: Silphinae)

Precise identification of insect species and their developmental stages (instars) on human remains is crucial for estimating the postmortem interval (PMI) and detecting potential body tampering. However, larvae of many common species can only be reliably identified using molecular techniques, which are not always possible. Furthermore, determining the instar stage is even more challenging, as features necessary for precise identification are often poorly documented. Oiceoptoma thoracicum (Linnaeus, 1758) is a common necrophagous beetle in the Palearctic region from the Western Europe to Japan. The species is also frequently found on cadavers of large vertebrates, including human remains, making it a promising candidate for use as a bioindicator in forensic entomology. Adults can be easily distinguished from other species; however, larvae have never been thoroughly described. The identification of O. thoracicum based on immature stages, or the differentiation of instars of this species is therefore not yet possible. The aim of this study was to provide reliable morphological characters that would allow the identification of larvae and instar stages in O. thoracicum. Quantitative and qualitative morphological characters for instar and species identification are described and illustrated. A list of described immature stages of the genus Oiceoptoma is provided.