Fig. 1

Male and female genitalia and phylogenetic relationships of Ohomopterus species used in this study. A Genital system and coupling of female and male genitalia in Ohomopterus beetles. B Measurements of the length and width of the vaginal appendix (upper) and copulatory piece (lower). C Phylogenetic relationships inferred from a restriction site associated DNA sequence data [15], vaginal appendix, copulatory piece, and habitus of adult beetles (upper: female; lower: male) of the four study species and the outgroup species, Carabus maiyasanus. D Relationships between length/width of the copulatory piece and vaginal appendix in the four study species. Photographs and illustrations by T. Sota