Description of the third instar larva of the stag beetle Prismognathus dauricus Motschulsky, 1860 (Coleoptera: Scarabaeoidea: Lucanidae) using electron microscopy.

Lucanidae have long received great attention for their adults. However, differentiating between the larvae of stag beetles is difficult and remains unsatisfactorily resolved due to the microscopic features separating groups. In the current study, the larvae of Prismognathus dauricus Motschulsky, 1860 were investigated using light and scanning electron microscopy. The larvae of P. dauricus are atypical for the following characters: i) the epipharynx possesses anteriorly eleven protophoba arranged in a semi-round line; ii) the par stridens consists of 31 ± 0.7 (N = 10) subconical teeth arranged in a slightly curved, longitudinal row; iii) the plectrum is composed of 60 ± 1.4 (N = 10) carinae; iv) the claws of thoracic legs are apically blunt and bear four setae. Moreover, the size arrangement of the larval spiracles also provides valuable taxonomic information. Our SEM study reveals larval ultramorphological characters useful for identification of this species for the first time.