Descriptions and Ecological Notes on the Larval Stage of Elmomorphus brevicornis Sharp, 1888 (Coleoptera: Dryopidae)

Larvae in the family Dryopidae are poorly known, and their ecology and life histories need further research. Elmomorphus brevicornis Sharp, 1888, which is distributed in Japan and Korea, is the only species of Elmomorphus Sharp for which larvae are known. In this study, we investigated the larval morphology and life history of E. brevicornis in the San'in region of Honshu, Japan. The larval morphology of E. brevicornis was almost identical to that of other Dryopidae larvae, closely resembling that of Dryops. The first- and second-instar larvae lacked spiracles, but from the third instar onward, spiracles were present on the side of the mesothorax and abdominal tergites I–VII and on the dorsolateral surface of tergite VIII. Oviposition occurred within plant root tissue in water, wherein hatched larvae lived until the second instar. A few third-instar larvae were collected from water and were presumed to be migrating to the soil. The largest larvae observed in the field had a prothorax width of approximately 0.7 mm and were estimated to be at the 11th instar.