The long-armed scarab beetles, a charismatic group within the small tribe Euchirini, are characterized by their large body sizes and distinctly elongated forelegs in males. While mitochondrial genomes have been sequenced for two of the included genera, Cheirotonus and Propomacrus, the type genus of the tribe, Euchirus, remains unexplored. It will provide valuable insights into the phylogenetic position and internal relationships of the Euchirini to investigate the mitochondrial genome of Euchirus and conduct phylogenetic analyses. In this study, it presents the first mitochondrial genome of Euchirus longimanus. The length of the mitochondrial genome of Euchirus longimanus is 16,591 bp. We analyzed its genes arrangement, base composition, codon usage frequency, and constructed phylogenetic trees based on the nucleic acid sequences of 13 protein-coding genes. The phylogenetic results are consistent with previous studies, confirming the phylogenetic position of Euchirini within the paraphyletic Melolonthinae. Notably, we firstly elucidate the phylogenetic relationship among all three genera: Propomacrus + (Cheirotonus + Euchirus), supported by robust values in Bayesian inference (BI) analysis. However, the maximum likelihood (ML) tree shows weaker support for the internal node of Euchirini and exhibits distinct topological variations compared to the BI tree, suggesting the potential paraphyly of Cheirotonus with the inclusion of Euchirus longimanus. These findings highlight the importance of including additional species of Euchirus and Cheirotonus in the future phylogenetic investigations to achieve a comprehensive understanding of their evolutionary relationships.
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