Maximum-likelihood tree of Nannarrup specimens and outgroups (Mecistocephalus guildingii, M. subgigas, and Dicellophilus carniolensis) based on the COI dataset. Nodal values are derived from Ultrafast bootstrap (UFBoot) and SH-like approximate likelihood ratio test (SH-aLRT). Asterisk (*) indicates values of 100% in UFBoot and SH-aLRT. A hyphen (-) indicates values <95% in UFBoot and <80% in SH-aLRT. Nodal values are not shown when both UFBoot and SH-aLRT values are <95% and <80%, respectively. The unit of evolutionary distance is the number of base substitutions per site. Ingroup specimens are shown as their specimen identification number. Abbreviations: Ao = Aomori pref.; Ak = Akita pref.; Iw = Iwate pref.; Ya = Yamagata pref.; Fs = Fukushima pref.; Ni = Niigata pref.; To = Tokyo pref.; Kn = Kanagawa pref.; Sh = Shizuoka pref.; Wa = Wakayama pref.; Hy = Hyogo pref.; Ok = Okayama pref.; Yu = Yamaguchi pref.; Ko = Kochi pref.; Eh = Ehime pref.; Fo = Fukuoka pref.; Mi = Miyazaki pref.; Kg = Kagoshima pref.