Comparative larval morphology of four Pteroptyx (Coleoptera, Lampyridae, Luciolinae) species in Thailand

Background Fireflies in the genus Pteroptyx are renowned for their significance in firefly tourism initiatives. Their occurrence and abundance have been extensively studied to facilitate sustainable utilization and conservation of their populations. As a group of highly charismatic insects, Pteroptyx fireflies play an important role in raising awareness and advocating for the conservation of mangrove forests. Previous taxonomic studies on these fireflies have primarily focused on adult while the larvae remain limited. Therefore, this study aimed to compare the larval morphology of four Pteroptyx species found in Thailand. Methods The characteristics of the larvae were examined under a microscope, and the species were identified by rearing the larvae to adult and comparing the adult males with previously identified male specimens. Additionally, morphometric analysis of the protergites was conducted to support identification efforts. Results Larval descriptions and an identification key for four Pteroptyx species were developed through the comparison of larval morphology, focusing on tergite texture, protergum shape, color patterns, mouthparts, and the holdfast organ (pygopod). Among the species, P. valida is uniquely characterized by lacking tubercles on the thoracic tergites and has a holdfast organ composed of more than 10 retractable filaments, clearly distinguishing it from the other three Pteroptyx species. Most species have a protergum length much longer than its width, except P. tener . An overview description of Pteroptyx larvae is provided with supplementary files summarizing the key characteristics of these four Pteroptyx larvae. Discussion Species-specific traits are evident among the four species, likely reflecting their specific biological and ecological requirements. Pteroptyx valida Olivier, 1909 displays distinct morphological characteristics, including features of the holdfast organ.