Morphometric traits of Dorcus parallelipipedus (Coleoptera: Lucanidae) larvae and adults: can differences between populations be ruled out?

Summary Stag beetles are saproxylic insects that live in deadwood colonised by fungi and other microorganisms. Due to the cryptic habits of these species, little is known on their biological aspects, especially for the immature stage. In this study, we investigated morphometric traits of lesser stag beetle, Dorcus parallelipipedus (Linnaeus, 1758) (Coleoptera: Lucanidae) larvae and adults, with comparisons between populations. Instar identification by measuring larval head capsule was performed, and the relationship between larval body mass and head capsule width was investigated for each surveyed population. To assess the differences among populations, the scaling relationships for adults between their body and mandibles length was also considered, especially for adult males. Morphometric relationships were described by exponential equations. Differences between populations were sometimes limited to one or the other feature, and particularly ascribed to the larval body mass. These differences could be imputed to several factors, among with those of environmental or genetic order. The scaling relationship of lesser stag beetle adult males showed a positive allometry but did not differ among populations, indicating that morphological traits within a species and sex may be biologically retained. Findings are discussed from the perspective of D. parallelipipedus life history.