Bryelmis rivularis Barr, 2011

Barr, Cheryl B., 2011, BryelmisBarr (Coleoptera: Elmidae: Elminae), a New Genus of Riffle Beetle with Three New Species from the Pacific Northwest, U. S. A., The Coleopterists Bulletin 65 (3), pp. 197-212 : 197-212

Bryelmis rivularis Barr , new species ( Figs. 7 , 8 , 10 , 13 )

Description. Length 1.84–2.36 mm, width 0.9–1.2 mm. Body color dark brown to black, or bicolored with broad orange to red-brown elytral vittae; carinae, sulci, striae, and punctures distinct. Antenna: Testaceous, often darker at tip. Head: Dark brown to black. Eyes weakly protuberant. Frons finely rugose with scattered small punctures bearing fine setae. Clypeus sparsely punctate with small punctures spaced more than 2X their diameters apart, bearing moderately long setae; integument between punctures smooth medially, finely rugose laterally. Labrum smooth with evenly spaced fine punctures bearing setae, apico-lateral margins with dense clusters of setae. Pronotum: Dark brown to black, shiny. Slightly wider than long, widest about 1/3 distance from base; length 0.56–0.72 mm, width at widest point 0.7–0.9 mm. Basolateral angles more or less forming right angles. Disc finely rugose with small, shallow, widely spaced punctures accompanied by fine setae; narrow, low, median longitudinal carina extending from near apical margin to basal margin. Sublateral carinae narrow but not sharply carinate; each bordered medially by a shallow, broad basal and a sulcate apical fossa. Elytron: Convex; shiny with short, sparse setae; color medium orange, red-brown or black, sometimes bicolored, dark medially with broad, red-brown, variably wide lateral vitta extending to lateral margin. Length 1.38–1.74 mm, width at widest point 0.44–0.62 mm. Disk lateral to suture with a shallow depression about 1/3 distance from base. A low sublateral carina present at interval 7, most developed at apical 1/3, abruptly ending at about 1/5 of the distance from the elytral apex; less distinct carina present at interval 8 ending about 1/3 the distance from the apex. Shallow longitudinal sulcus with deeper fovea containing enlarged punctures adjacent to metasternum. Leg: Shiny red-brown except for distal 1/4–1/3 of femur which is dark brown; visible portion of femur dark in dorsal habitus view. Femur with closely spaced, small punctures and sparse setae. Venter: Shiny, red-brown to dark brown medially, prosternum darkest; dense silver to golden plastron present laterally. Apex of prosternum broadly rounded. Mesosternal disc shallowly concave between mesocoxae. Metasternal disc flat to slightly convex. Male genitalia ( Fig. 7 ): Parameres narrowed medially, then flared laterally at tips, each producing an obtuse angle. Penis slightly longer than parameres, more or less parallel-sided to apical third, then narrowed to acuminate tip.

Variation. The most conspicuous variable among individuals is the color of the elytra, which can range from orange to black, or be more or less vittate with orange or red-brown laterally and a black stripe at the suture. Less noticeable are differences in the size and depth of the elytral depression at the basal 1/3. Metathoracic wings may be present or absent. Measurements of the length of the longest and shortest specimens showed size overlap between males (n = 4) and females (n = 4), with both the longest and shortest being males.

Comparative and Diagnostic Comments. Bryelmis rivularis is unique among the three species in having male genitalia with the paramere tips angled outward ( Fig. 7 ). In addition, some individuals are bicolored, having broad, red-brown elytral vittae lateral to the midline ( Fig. 8 ). Externally, this species most resembles B. siskiyou ( Fig. 9 ), but differs in that the median pronotal carina is distinct, the sublateral pronotal carinae are often more pronounced, and the elytra are more deeply striate with larger punctures. In B. siskiyou , the median pronotal carina is reduced, the sublateral pronotal carinae are distinct but less prominent, and the elytra are not as deeply striate and punctate, giving the body a smoother appearance. Bryelmis idahoensis ( Figs. 3, 4 ) is more rugose and sculptured with prominent carinae, sulci, striae, and punctures. Unlike B. rivularis and B. siskiyou , the median pronotal carina is produced and ridgelike, the pronotal disc is smooth with few punctures and setae, the lateral elytral sulcus is deep and trench-like, and the male genitalia have the tips of the parameres unbent ( Fig. 5 ).

Material Examined. 139 specimens. HOLO- TYPE ♂ in EMEC, labeled “WA: Jefferson Co., Hell Roaring Cr. at Upper Hoh Rd. just NE jct. US Hwy. 101, ∼ 13 rd. mi. SSE Forks, 1-VI-1992, coll. C.B. Barr // HOLOTYPE Bryelmis rivularis Barr ” [red label]. Ninety-six paratypes (P) [yellow labels] and 42 non-paratypes ( NP) were examined from the following localities: Same data as holotype (4 P, BNHM; 4 P, CASC; 4P, CNCI; 25 P, 17 NP, EMEC; 2 P, LSAM; 4 P, OSAC); OREGON: Benton Co. : Siuslaw NF, trib. Crooked Cr. along Marys Peak Rd. 0.3 mi. W jct. Hwy. 34, 28-VI-1985 , C. B. Barr (2 P, EMEC); Siuslaw NF, Marys Peak Campgrd., Parker Cr. , el. 3600′, 9-VIII-1983, R.W. Wisseman coll. // extracted from moss on margin of stream with berlese funnel (2 P, EMEC; 1 NP, ABAC); Mary’ s Peak, 85/6/28, H.P.B. [Harley P. Brown] (1 P, OMNH); Siuslaw NF, Marys Peak Rd. , day use area, 23-VI-2004, coll. R. E. Roughley & R. D. Kenner // elev. ca. 930 m, 44° 30′15.60″N, 123° 33′43.10″W (1 P, SMDV). Clatsop Co.: Lewis & Clark R., 85/7/1, H. P. Brown (1 P, OMNH); Lewis & Clark River , Saddle Mtn. S.P. road., 1-VII-1985 , C. B. Barr // small tributary (4 P, EMEC); Lewis & Clark R. at Saddle Mtn. Rd., 8 km. N jct. Hwy. 26, 23-VI-2004, coll. R. E. Roughley & R. D. Kenner (1 P, SMDV) . Columbia Co.: Fall Creek along Hwy. 47, 2.7 mi. WSW Clatskanie, 3-VI-1992 , C. B. Barr (8 P, 2 NP, EMEC). Marion Co.: Silver Falls SP, S fork Silver Crk. ca 16 mi SE Salem, 26 Oct 1985 , R S & V L Zack collectors (1 P, WSUC). WASHINGTON: Clallam Co.: Beaver Crk., ca 2 mi N of Sappho, R12W T30N Sec 20, 24 June 1992, R. S. Zack collector (1 P, WSUC) . Grays Harbor Co.: Olympic NF boundary, Donkey Cr. at FS Rd. 22, ∼ 10 air mi. NE Humptulips , 2-VI-1992, coll. C.B. Barr (3 P,

EMEC); Moclips , Moclips Riv., T 20N R12 W Sec 8, 23 June 1992, R. S. Zack (1 P, EMEC; 2 P, WSUC) . Jefferson Co.: Hell Roaring Cr. at Upper Hoh Rd. just NE jct. US Hwy. 101, ∼ 13 rd. mi. SSE Forks, 2-VII-1985, C. B. Barr (12 P, 6 NP, EMEC) ; Forks (7 mi SE), 12 July 1988, P.J. & R.E. Spangler, P.D. Perkins // collected in Hell Roaring Creek, colln. #10, (2 P, MCZC; 8 P, 15 NP, USNM); Hell Roaring Crk. ca. 12 mi SSE Forks, T27N R12 W Sec 21, 23 June 1992, R. S. Zack collector (4 P, WSUC) .

Distribution, Habitat, and Biology. Based on collection records, B. rivularis inhabits the Coast Ranges from the Olympic Mountains of northwestern Washington, south to northwestern Oregon where it also occurs in the western Cascades ( Fig. 10 ).

The type locality, Hell Roaring Creek ( Fig. 13 ), is near the Hoh Rainforest area of Olympic National Park in Washington. This is the only known locality to yield more than a few specimens of the species. The water is tea-colored due to tannins in the allocthonous input from the surrounding coniferous forest, and much coarse, woody debris is present in the stream. In the areas where specimens were collected, the stream bed ranges from 3–6 m wide and the water depth is generally less than 0.3 m. The substrate is sandy gravel and cobbles less than 30 cm in diameter, and occasional larger boulders. A series of 54 specimens of B. rivularis collected in June 1992 had a sex ratio of 28 females to 26 males.

Microhabitat preference for bryophytes was examined during a second visit to Hell Roaring Creek, and was found to be the aquatic liverworts C. polyanthos rivularis and Scapania undulata (L.) Dumort ( Scapaniaceae ). A more in-depth look at microhabitat preference at this locality is contained in the Discussion section.

The four other streams where I have collected B. rivularis ranged from small (1.5–3.0 m wide) with cobbles and sandy gravel, to large (> 7.5 m) with swift water, bedrock ledges, and small waterfalls. Despite the dissimilarities in stream type, in all cases B. rivularis was found among aquatic bryophytes attached to rocks. Several species of Elminae inhabit three of the streams, including the type locality, but only B. rivularis occurs in the two smaller streams. I have recorded the following elmid species co-occurring with B. rivularis at one or more of the collecting localities: C. addenda , Heterlimnius koebeli (Martin) , L. avara , Narpus angustus Casey , N. concolor , O. quadrimaculatus , Zaitzevia parvula (Horn) , and Z. posthonia .

Etymology. The specific epithet, rivularis , from the Latin rivulus or rivali s, meaning “stream or brook”, is taken from the name of the aquatic liverwort with which it has been most commonly associated, C. polyanthos rivularis .

Figures

Figs. 5–7. Male genitalia of Bryelmis spp. 5) B. idahoensis, dorsal view; 6) B. siskiyou, dorsal view; 7) B. rivularis, a) Dorsal view, b) Lateral view.

Figs. 8–9. Habitus of Bryelmis spp. 8) B. rivularis, a) Dorsal, b) Lateral; 9) B. siskiyou, a) Dorsal, b) Lateral. Scale bars = 0.5 mm.

Fig. 10. Known distribution of Bryelmis spp. in North America: B. idahoensis (circles), B. rivularis (squares), and B. siskiyou (triangles).

Figs. 11–13. 11) Fern Creek, Clearwater Co., ID, type locality of Bryelmis idahoensis; 12) Dragsaw Spring, Humboldt Co., CA, habitat of Bryelmis siskiyou; 13) Hell Roaring Creek, Jefferson Co., WA, type locality of Bryelmis rivularis.

Figs. 3–4. Habitus of Bryelmis idahoensis. a) Dorsal, b) Lateral. Scale bars = 0.5 mm.