Morphological study on the mouthparts of four adult Aphodiinae beetles (Coleoptera: Aphodiinae)

Abstract

Aphodiinae belong to Scarabaeidae, which are important environment-cleaning insects. In this study, the ultrastructural characteristics of the mouthparts (including the epipharynx, mandible and maxillae) of adult Aphodiinae, namely, Phaeaphodius rectus, Colobopterus erraticus, Paracrossidius transmontanus and Rhyparus sp., were systematically studied. The results are as follows: I. Rhyparus sp. exhibits saprophagy, while the others exhibit coprophagy. II. The three kinds of coprophagous Aphodiinae are all likely to feed on fresh dung. Among them, C. erraticus not only feeds on dung with the highest moisture content but also ingests solid food particles with the smallest diameter. Saprophagous Rhyparus sp. can ingest solid food particles with the largest diameter but feeds on humus with the lowest moisture content. The mouthpart structures of the Aphodiinae were highly consistent with their feeding habits. III. The findings support the utility of the epipharynx as an important morphological characteristic for classification of Aphodiinae at the genus and higher taxonomic levels. However, whether this inference is valid still needs to be verified by molecular biological data. In conclusion, the results of this study not only complement morphological information on the mouthparts of Aphodiinae but also provide basic data for further research on the evolution of the mouthparts of Aphodiinae.