Athoplastus acutus ( Knull, 1946 ) Etzler & Johnson, 2018

Etzler, Frank E. & Johnson, Paul J., 2018, Athoplastus Johnson and Etzler (Coleoptera: Elateridae: Dendrometrinae), a New Genus of Click Beetle from the Northwestern Continental USA, The Coleopterists Bulletin 72 (3), pp. 503-521 : 513-516

Athoplastus acutus ( Knull, 1946) , new combination

(Adult: Figs. 1 , 5–7, 9–10, 12, 15–18 ) (Larva: Figs. 31–46 )

Aplastus acutus Knull 1946: 142

Ctenicera acutus Knull 1957: 202

Ctenicera idahoensis Knull 1958: 154 . Invalid replacement name to prevent homonymy with Athous acutus Mulsant and Guillebeau, 1855 (= Metanomus infuscatus (Eschscholtz, 1829)) . The Mulsant and Guillebeau name was considered a junior synonym of Metanomus infuscatus (Eschscholtz) since de Buysson (1887) but never appeared as a valid taxon name in combination with Ctenicera , so no homonymy exists (see ICZN 1999, Art. 60.2).

Diagnosis. Males of A. acutus have the prosternum dorsoventrally flattened until it reaches the procoxae, where it is abruptly expanded ventrally ( Fig. 9 ). Males of other species of the genus have the prosternum gradually expanding ventrally toward the procoxae ( Fig. 8 ). Antennomeres 6 and 7 usually have a secondary expansion at approximately twothirds of total length from base, which is not present in the other species ( Fig. 12 ). This character may be difficult to see or absent in some specimens, but it is usually visible on other antennomeres. Females have a slight impression on the prosternum anterad the procoxae and setae on the scutellum that are mostly projecting posteriorly.

Description. Male. Length 15.0– 17.5 mm, width 3.5–4.0 mm (measured across bases of elytra). Yellow-brown to dark brown ( Figs. 1 , 6–7 ). Head: Ocular index = 55.0–63.6 (mean = 58.1; mode = 60; n = 30). Antenna: Mean ratio of antennomeres [antennomere length relative to pedicle (antennomere 2)] 2–11: 1: 1.4: 3.5: 3.9: 3.9: 4.1: 4.1: 4.1: 3.9: 4.8 (n = 11). Antennomeres 6 and 7 often with secondary expansion at 2/3 total length (see Fig. 12 ). This character may also be on other antennomeres but is usually less pronounced. Pronotum: 1.2–1.7X wider than long. Lateral margin sinuate anterad divergent hind angles, widening just anterad midlength, lateral carina dorsoventrally flattened on anterior half. Punctures distinct, subumbilicate and dense on disc, separated by less than half their own diameter, although some specimens have impunctate areas just laterad midline; punctures becoming clearly umbilicate and denser along anterior and lateral margins. Prosternum: Dorsoventrally flattened with dense, shallow, umbilicate punctures; anterior lobe short, broadly rounded, shallowly deflexed. Posterior process short and arcuate, distinctly raised ventrally between procoxae, then sharply deflexed dorsally before ending in small hook; midline of prosternum often with raised section just anterad procoxal rise, sometimes nearly carinate, flanked by indentations in prosternum. Legs: Tarsomere 5 equal in length to tarsomere 1 on pro- and mesotarsi, tarsomere 5 equal in length to tarsomere 2 on metatarsi. Elytra: Elongate, subparallel, 5.2X pronotal length; striae shallowly impressed, deeper basally and apically, punctures evanescent; intervals shallowly convex, punctures rough, shallow, and irregularly distributed. Aedeagus ( Figs. 16–18 ): Basal piece about 1/3 total length, with triangular membranous section on ventral surface ( Fig. 17 ); median lobe 1.3X length of parameres, slightly deflexed ventrally at tip, median carina on ventral surface, basal struts coming off at an obtuse angle; parameres wide basally, edges sinuate and distinctly narrowing toward tip, tip with acute lateral expansion bearing 4–6 setae, either blunt or sharp ( Fig. 18 ).

Female. Length 21–26 mm, width 5–6 mm (measured across bases of elytra). Yellow-brown to red-brown ( Fig. 5 ). Head: Ocular index = 70.8–74.1 (mean = 72.7, n = 3). Antenna: Mean ratio of antennomeres 2–11: 1: 1.2: 2.1: 1.9: 1.9: 1.8: 1.7: 1.6: 1.5: 1.7 (n = 3). Note: Values for antennomeres 8, 10, and 11 are each based only on two specimens. Pronotum: As wide as or 1.1X wider than long. Lateral edge sinuate anterad divergent hind angles, widening just anterad midlength. Scutellar shield: Setae directed posteriorly.

Specimens Examined (45). Males. Holotype. USA: IDAHO: [Shoshone Co.], Wallace; 14.iv.[19]40, Otto Huellemann ( FMNH) . Paratypes. USA: IDAHO: [Shoshone Co.], Wallace , 14.iv.1940, [Otto Huellemann?] (2, FSCA; 1, FMNH); Wallace, Otto Huelleman (1, FMNH) .

Other Male Specimens Examined. USA: IDAHO: [Kootenai Co.] Ft. Sherman [Coeur d’ Alene], Mch. [March?] 1896, J. C. Merrill (1, USNM) ; 4 th of July Summit , 30.iv.1974, W. F. Barr (1, WFBM) ; Kidd Island Bay , 1987, E. Cardwell (1, WFBM) ; Latah Co., Harvard, Laird Pk , 03.iv.1962, S. D. Smith, attracted by U.V. light (1, USNM; 4, WFBM); Near Moscow , Spring 1932, P. L. Rice (1, USNM) ; Sect. @ Pond; Moscow, 01.v.[19]57, D. T. Allison, Collector (1, WFBM) ; [Shoshone Co.] Clarkia , 8.iv.1934, I. W. Bales (1, USNM) ; Wallace , 8.iv.1939, Huelleman (1, USNM) ; Wallace , 14. iv.1939, Huelleman (1, FMNH) ; Wallace, 26.iv.39, Huelleman (2, FMNH) ; Wallace , 1.v.1939, Huelleman (1, FMNH) ; Wallace, 9.v.39, Huelleman (1, FMNH) ; Wallace , 20.vii.1939, Huelleman (1, FMNH) ; Wallace, [no date], Huelleman (1, FMNH) ; Wallace , 12–20.iv.1940, O. Nudlemann [likely a mistype of Huelleman] (3, FMNH) . MONTANA: Lincoln Co., Jnct. Kootenai & Yaak Rs. , 48.5855°N, 115.9769°W, 12.iv.-03.vi.2014, [elev.] 1927ft, C.J. Hart, Lindfnl [with] PSB [lure] (1, MTEC, MTEC019710 ) ; Ravalli Co., Rombo Campgrd , 45.7644°N, 114.2815°W, 25. iv.2013, [elev.] 4505ft, F. E. Etzler , Handnet at Night (1, MTEC010381 ) ; Rombo Campgrd , 45.7680°N, 114.2810°W, 04.v.2013, [elev.] 4508ft, F. E. Etzler , Handnet at Night (1, MTEC) ; Rombo Campgrd , 45.7642°N, 114.2818°W, 19.iv.2014, [elev.] 4505ft, F. E. Etzler , Blacklight (8, MTEC) . WASHINGTON: Stevens Co., Pleasant Valley , 4.v.1957, on maple, A. R. Gittins Collector (1, WFBM) .

Females. USA: IDAHO: [Latah Co.], Moscow Mt. , iv.[19]12, Idaho (1, USNM) ; Moscow , 23.iv.1955, F. T. Cook (1, USNM; 1, WFBM) . MONTANA: Mineral Co., Trout Creek Camp, 17.iii–22.vi.1995, D. L. Gustafson, pitfall trap (1, MTEC) ; Ravalli Co., Sand Crk - Blue Joint [Crk], 05.x.1996 – 06.vi.1997, D. L. Gustafson, pitfall trap (1, MTEC) ; Rombo Campgrd , 45.7644°N, 114.2815°W, 25.iv.2013, [elev.] 4505ft, F. E. Etzler , handnet at night (1, MTEC010382 ) .

Larvae. USA: IDAHO: Moscow Mtn , 15.v.1951, Lane-Downie (2, USNM) . MONTANA: Mineral Co., Trout Creek Campground, 47.1174°N, 114.8673°W, 25.iv–19.vi.2013, elev. 2940ft, F. E. Etzler , pitfall (1, MTEC, MTEC008126 ) ; Ravalli Co., Blue Joint Creek , base of stump, 45.6985°N, 114.3586°W, 26. iv–5.v.2013, elev. 4960ft, F. E. Etzler , pitfall (1, MTEC, MTEC019709 ) ; Rombo Campground , 45.7680°N, 114.2810°W, 4.v.2013, elev. 4508ft, F. E. Etzler , by hand (1, MTEC, MTEC019713 ) .

Distribution. This species is known from westernmost Montana, northern Idaho (north of Idaho County), and the northeast corner of Washington State ( Fig. 29 ).

Taxonomic Remarks. This species is represented by the greatest number of specimens and has the broadest known species range of the four species in the genus.Due to this and the soft-bodiedness of the species, variation exists among specimens. However, no clear link to locality or date of collection was discovered.The presence of impunctate areas on either side of the midline is very rare, only occurring in a small number of northern Idaho specimens.Subtle variation also exists in male genitalia, but again there is no link to locality or collecting date. Mitochondrial DNA was amplified for Montana specimens. These results are discussed below. This is the only known species with associated larvae and ecological notes.

Field Notes. The collecting localities of the Montana specimens of A. acutus were visited in early spring of 2013 to place pitfall traps in an attempt to capture fresh specimens and reliable DNA samples. While camped at Rombo Creek Campground near one of the localities of the MTEC females, the first author was examining trees around the campsite at dusk when a female was collected at the base of a ponderosa pine. A few minutes afterwards, a male was collected at the same spot, then additional males were observed flying and a few more collected.

The collecting site was revisited in 2014, and specimens were collected at an ultra-violet (UV) light set up near a white sheet. Field observations were recorded and are discussed below. Larvae were collected at three Montana sites and tentatively associated with adults. Due to the apparent adult sexual dimorphism and lack of reared larvae, we confirmed associations using DNA barcoding.

Figures

Figs. 1–4. Athoplastus species, dorsal habitus. 1) A. acutus; 2) A. palouse; 3) A. lochsa; 4) A. rainieri.

Figs. 5–9. Athoplastus species. 5) A. acutus, female dorsal habitus; 6) A. acutus, male dorsal habitus, darker coloration; 7) A. acutus, male ventral habitus; 8) A. rainier, prothorax, lateral view (arrow indicates start of area between procoxae); 9) A. acutus, prothorax, lateral view (arrow indicates start of expanded area between procoxae).

Figs. 10–15. Athoplastus species. 10) A. acutus, prothorax, dorsal view; 11) A. lochsa, prothorax, dorsal view; 12) A. acutus, left antenna; 13) A. lochsa, left antenna; 14) A. palouse, left antenna; 15) A. acutus, female, left wing. Scale bars for antennae = 1 mm; for wing = 5 mm.

Figs. 16–27. Athoplastus species, adeagi, dorsal view, ventral view, and close up of paramere apex, respectively.

Figs. 31–42. Athoplastus larva MTEC008126, dorsal, lateral, and ventral views, respectively. 31–33) Head and prothorax; 34–36) Meso- and metathoraces; 37–39) Abdominal segments 2 and 3; 40–42) Ninth abdominal segment.

Figs. 43–46. Athoplastus larval characters. 43) Ninth abdominal segment of medium-sized larva, MTEC019709; 44) Ninth abdominal segment of small larva, MTEC019713; 45) Frontoclypeal region, dorsal view, detail from Fig. 31, pes = postepicranial seta; 46) Divided prosternum, detail from Fig. 33. Scale bars = 1 mm.

Figs. 28–30. Athoplastus species. 28) A. rainier, female, internal genitalia, v = vagina, u = uterus, acgld = accessory gland, bc = bursa copulatrix (after Han et al. 2012); 29) Distribution map of examined specimens, with rivers; 30) Neighbor-joining tree of Montana populations of A. acutus, COI mtDNA, 500 runs, scale bar = 1% difference.