Postembryonic development and morphological variations of larval instars in the scorpionfly Panorpa liui Hua...

The larva is the feeding and growing stage of holometabolous insects that undergo complete metamorphosis. However, morphological variations among instars remain largely unknown for many insect groups, especially for the relict Mecoptera. Here, morphological variations among instars for the scorpionfly Panorpa liui Hua were investigated using light and scanning electron microscopy. The results show that the first instar is distinguishable from the following instars by the presence of an egg burster in a brown patch on the frons. The second instar can be separated from the following instars by the cranial suture 2/5 rather than 1/2 as long as the head. The third instar is differentiated from the fourth instar by the annulated setae with microtricia rather than bald on the basal part. These results may provide new data for instar identification of Panorpidae larvae.