Stenichnus (Stenichnus) lackneri Jałoszyński

(Figs 33–38)

Stenichnus (Stenichnus) lackneri Jałoszyński, 2016: 148.

Material studied. JAPAN, Kagoshima Prefecture: 1 ♁, 1 ♀, Amami-Ôshima, Yui-dake, 18.03.2010, sifted, leg. T. Lackner (cPH, cPJ); Okinawa Prefecture: 2 ♁♁, Okinawa-jima, Kunigami District, Nakijin, Imadomari, 05.06.2020, leg. Norihide Tokushige (cPJ).

Distribution. Japan: Ryukyus: Tokunoshima, Amami-Ôshima and Okinawa-jima.

Remarks. This species was described based on a single male collected on a relatively small northeastern Ryukyuan island of Tokunoshima (Jałoszyński 2016), which is a part of Amami Archipelago and is situated ~ 50 km SW of the largest island of this group, Amami- Ôshima. The occurrence of S. lackneri on the latter island is reported here for the first time, and also for the first time this species is demonstrated to inhabit the largest island of the Ryukyus, Okinawa-jima.

The males from Tokunoshima and Amami-Ôshima do not differ in external features (the holotype of S. lackneri was examined during the current study), and their aedeagi (Fig. 35 and 36, respectively) do not show any differences. The two males collected ~ 150 km SW of Amami-Ôshima, on the large island of Okinawa-jima, show slight differences both in external morphology and in male genital features compared to the holotype. The specimens from Amami Archipelago (Fig. 33) are slightly less convex, and have slightly smaller pronota in relation to elytra than those from Okinawa-jima (Fig. 34). Their aedeagi (Figs 35, 36) have shorter apical projections, the subapical endophallic plate about as long as broad, and the membranous inner sack situated in the basal region of the median lobe closer to the plate than in specimens from Okinawa-jima (Figs 37, 38). With only four males, it is impossible to draw any general conclusions regarding possible specific or subspecific differences between the Amami and Okinawan populations. They are both provisionally included in one species, S. lackneri, pending further study when more specimens become available.