Dyscharachthis amplicollis (Fleutiaux, 1923)

Otto, Robert L., 2024, Three additions to the false click beetle (Coleoptera: Elateroidea: Eucnemidae) fauna in the Nearctic region, Insecta Mundi 2024 (47), pp. 1-14 : 7-9

Dyscharachthis amplicollis (Fleutiaux, 1923)

Fig. 5–8

Galloisius amplicollis Fleutiaux 1923: 295

Differential diagnosis. Basally closed, lateral antennal grooves will readily distinguish this eucnemid apart from all primitive eucnemids, members of the subfamilies Melasinae and Macraulacinae . Presence of one apical spur on the prothoracic tibiae will further distinguish the species from members of the tribe Dendrocharini Muona. Absence of the excretory grooves on the basolateral area of the hypomeron will also distinguish D. amplicollis from Idiotarsus errans (Horn) and species of Eucnemis Ahrens. Form and coloration of the species’ habitus will distinguish this eucnemid species from members of the tribes Proutianini Muona and Mesogenini Muona.

Specimens examined. Eighteen specimens were available for study: UNITED STATES of AMERICA: GEORGIA: Chatham County: “GEORGIA: Chatham Co. / 2.3 km WNW of Garden / City, 32.1235, −81.17599, 5m / 19 Apr–3 May 2022, LFT / E. Kennedy ” (1, GERP) ; “GEORGIA: Chatham Co. / 3.4 km S of Garden City / 32.08385, −81.15543 / 7m, 14–28 June 2022 / E. Kennedy ” // “ Cross-vane panel trap / + Geranyl acetol + / Spruce Blend + EtOH” (1, CMNH) ; “GEORGIA: Chatham Co. / 2.3 km WNW Garden City / 32.12351, −81.17598, 5m / 1–16 Sept. 2022, LFT / E. Kennedy ” (1, CMNH) ; “GEORGIA: Chatham Co. / 2.4 km WNW Garden City / 32.12402, −81.17636, 5m / 18 April–2 May 2023, LFT / T. Brackney ” (4, CMNH) ; “GEORGIA: Chatham Co. / 5.2 km W Port Wentworth / 32.15330, −81.21786 / 24 April–8 May 2023 ” // “Cross-vane panel / trap + Megaplatypus / lure, Chris Barnes” (1, CMNH) ; “GEORGIA: Chatham Co. / 1.5 km W Port Wentworth / 32.15127, −81.17904 / 11 m, 25 April–9 May 2023 ” // “Cross-vane panel / trap + Megaplatypus / lure, Chris Barnes” (1, CMNH) ; “GEORGIA: Chatham Co. / 3.4 km S of Garden City / 32.08372, −81.15545 / 4 m, 2–17 May 2023 / Timothy Brackney, coll.” // “ Cross-vane panel trap / with Geranyl acetol + / Spruce Blend + EtOH” (3, CMNH) ; “GEORGIA: Chatham Co. / 3.3 km ESE Savannah / 32.07249, −81.06748 / 1 m, 2–17 May 2023, LFT / T. Brackney ” (2, CMNH) ; “GEORGIA: Chatham Co. / 1.5 km W Port Wentworth / 32.15127, −81.17904 / 9–24 May 2023, LFT / C. Barnes ” (1, CMNH) ; “GEORGIA: Chatham Co. / 3.4 km S of Garden City / 32.08372, −81.15545 / 4 m, 17–30 May 2023 / Timothy Brackney, coll.” / “ Cross-vane panel trap / with Geranyl acetol + / Spruce Blend + EtOH” (1, CMNH) ; “GEORGIA: Chatham Co. / 1.9 km ESE Garden City / 32.10783, −81.13543 / 4 m, 17–30 May 2023 ” // “Lindgren FT / T. Brackney ” (1, CMNH) ; “GEORGIA: Chatham Co. / 3.4 km S of Garden City / 32.08367, −81.15481 / 30 May–13 June 2023 ” // “Lindgren FT / T. Brackney ” (1, CMNH) .

Redescription. Length, 4.5–6.0 mm. Width, 1.0–2.0 mm. Body oblong, robust, cuneiform; uniformly dark brown; scape dark brown, pedicel and antennal flagellum dark reddish brown; legs dark reddish brown; head, pronotum and elytra clothed with short, recumbent yellowish setae ( Fig. 5 ). Head ( Fig. 6 ): Subspherical, with delicate median carina present, extending down to frontoclypeal region where it splits and diverges along each lateral side of frontoclypeal region; interantennal carinae absent at base of frontoclypeal region; surfaces shiny, punctures somewhat shallow, evenly dispersed; apical margin of frontoclypeal region feebly rounded, more than 2 times wider than base; mandibles stout, bidentate, densely punctate. Antennae ( Fig. 7 ): Flagellomeres I–IX weakly serriform, about 1/3 of body length; flagellomere I longer than II; flagellomeres II–VIII quadrate, sub-equal; flagellomere IX 1.5 times longer than VIII; lateral carina present on antennal pedicel and each of the antennal flagellomeres I–VIII. Pronotum: Surfaces shiny; punctures shallow, evenly dispersed; slightly longer than wide, with enlarged, sharp hind angles; lateral sides parallel-sided at basal 2/3, apical 1/3 arcuate, narrowed craniad; disc convex; basal median groove variable, extremely shallow to absent; base sinuous. Scutellar shield: sub-triangular-shaped, slightly longer than wide, punctate with shallow median groove and distally rounded. Elytra: Striae largely absent except along elytral suture; interstices flattened; surfaces shiny; punctures deep and closely spaced near base, very shallow and widely spaced towards elytral apices. Legs: First tarsomere as long as the combined length of remaining four on mesothoracic and metathoracic tarsi; tibiae flattened in cross section; lateral surface of mesothoracic and metathoracic tibiae with setae only; metathoracic tarsomeres I–III simple; metathoracic tarsomere IV excavate-emarginate, as wide as III; metathoracic tarsomere V short; pretarsal claws simple. Venter ( Fig. 8 ): Punctures somewhat shallow, evenly dispersed; surface with recumbent yellowish setae; hypomeron with basally closed, lateral antennal grooves; metathoracic episterna parallel-sided; metathoracic coxal plates medially 2.5 times wider than laterally.

Distribution. This rarely collected eucnemid species has been taken from Japan (Amami-Oshima, Hokkaido, Honshu, Kyushu, Ogasawara (Chichi-Jima Island) and Shikoku), Laos, Singapore, Taiwan, Thailand, United States and Vietnam ( Suzuki 2016; Suzuki and Makihara 2020; Otto, pers. obs.). In the United States, D. amplicollis has been recorded from a number of localities within a single county in Georgia.

Biology. Eleven specimens were taken from Lindgren funnel traps. Seven specimens were taken from baited cross-vane traps. Larvae and pupae remain unknown. Much of the biological information associated with this species comes from Japan through the published works of Wataru Suzuki and his colleagues. Suzuki and Tao (2019) noted D. amplicollis has been known to breed in the dead wood of Japanese Hackberry ( Celtis sinensis var. japonica (Planchon) Nakai ( Cannabaceae )). They surmised the species utilizes the exposed dead sapwood of a living tree as a possible source to breed. They collected a number of adults on a plane tree (Plantanus species ( Plantanaceae )) along the roadside on a sunny day between the hours of 10:00 am to 1:00 pm with the temperatures ranging from 22.0° C to 30.5° C where they were observed crawling on the exposed sapwood in the middle of the day. They have noted the adults have been attracted to lights and found hiding beneath the bark of C. sinensis var. japonica and the zelkova tree ( Zelkova serrata (Thunburg) Makino ; Ulmaceae ). Suzuki and Makihara (2020) noted a number of examined adults were taken from light traps on Chichi-Jima Island within the Ogasawara Islands.

Subfamily Macraulacinae Fleutiaux, 1922

Diagnosis. Form oblong, elongate or obtuse; antennal flagellomeres usually sexually dimorphic; mandibles either stout with a basal tooth or slender without teeth; simple lateral pronotal ridge present; hypomeron either simple, with basally closed lateral antennal grooves or with basally open lateral antennal grooves; legs slender; prothoracic tibiae with one apical spur; lateral surfaces of mesothoracic and metathoracic tibiae usually with transverse rows of spines; tarsomere IV often bilobed; tarsal claws either simple or basally toothed; prothoracic tarsomere I usually with basal sex combs in males; male aedeagus with dorsally open basal piece; median lobe simple, with solidly fused slender basal struts; fused to lateral lobes; lateral lobes entire, either notched or apically deeply and narrowly bifurcate; bursa either simple or divided; spermatheca tripartite, sclerotized, divided ( Muona 1993; Otto 2016).

Tribe Macraulacini Fleutiaux, 1922

Diagnosis. Form oblong, elongate or obtuse; antennal flagellomeres usually sexually dimorphic; mandibles either stout with a basal tooth or slender without teeth; simple lateral pronotal ridge present; hypomeron either simple, with basally closed lateral antennal grooves or with basally open lateral antennal grooves; legs slender; prothoracic tibiae with one apical spur; lateral surfaces of mesothoracic and metathoracic tibiae usually with transverse rows of spines; tarsomere IV often bilobed; tarsal claws either simple or basally toothed; prothoracic tarsomere I usually with basal sex combs in males; male aedeagus with dorsally open basal piece; median lobe simple, with solidly fused slender basal struts, fused to lateral lobes; lateral lobes entire, either notched or apically deeply and narrowly bifurcate; bursa either simple or divided; spermatheca tripartite, sclerotized, divided ( Muona 1993; Otto 2017).

Figures

Figures 5–8. Dyscharachthis amplicollis (Fleutiaux). 5) Dorsal habitus. 6) Head, frontal view. 7) Antenna. 8) Ventral habitus. (Scale: 6, 7 = 0.5 mm; 5, 8 = 1.0 mm)