Possible Indicators of Feeding Habit Types: Analysis of the Mouthparts of Five Dichotomius Hope (Coleoptera: Scarabaeidae) Species from Argentina

Abstract Dung beetles exhibit a wide range of trophic preferences, including soft and hard resources. The study of mouthparts associated with these resources is extensive, and mouthparts of these insects have generally been described as membranous, hairy, and poorly adapted to cutting hard food. In this study, we compare the mouthparts (epipharynx, labium, and hypopharynx) of five species of Dichotomius Hope from Argentina that show differences in their trophic preferences, to evaluate if these structures also differ according to their feeding habit. We found epipharyngeal teeth, hypopharyngeal teeth, and more sclerotized structures in species that consume hard resources [Dichotomius carbonarius (Mannerheim)] and the absence or reduction of these structures in species that consume soft resources [Dichotomius sericeus (Harold), Dichotomius nisus (Olivier), Dichotomius mormon (Ljungh), and Dichotomius depressicollis (Harold)]. On the other hand, the latter species have hairier and softer mouth structures associated with these soft resources. According to these results, a detailed study of the macrostructures of mouthparts could indicate a priori the resource state consumed by a dung beetle species: the presence or absence of teeth and sclerotized structures would be associated with hard or soft food as the main resource, respectively, despite the occasional use of other resources in the field.