Bryelmis 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 Barr , new genus

( Figs. 1–9 )

Type Species. Bryelmis rivularis Barr , new species, here designated.

Adult Description. M a l e. B o d y e l o n g a t e - ovoid, approximately twice as long as wide, robust, convex dorsally and ventrally, well-sclerotized ( Figs. 1 , 3–4 , 8–9 ). Head: Prognathus, punctate with moderately long, pale setae. Antenna filiform, with 11 antennomeres; basal antennomere 1/3X longer than antennomere 2; antennomeres 3–10 about the same length as antennomere 2 but narrower, about 1/2X width of first 2, size slightly increasing distally; ultimate antennomere fusiform, 2X as long as the penultimate, bearing a cluster of short, dense setae at tip. Eye ovoid, well-developed. Clypeus rectangular, extending basally beneath antennal insertions, anterior angles broadly rounded. Mandible dark basally, lighter apically, with 3 long, slender teeth, tips narrowly rounded; prostheca transparent with 4 fine apical teeth. Maxillary palpus 3-segmented; apical segment fusiform, slightly asymmetrical, longer than previous two segments; basal segment 1/2 the length of the second segment. Labrum rectangular, narrower than clypeus; apicolateral, and occasionally mediolateral, margins with dense fringe of pale, stout setae. Labial palpus 3-segmented, apical segment subovoid, as long as basal 2 segments and 2X as wide. Gena and gula with dense, yellow plastron. Pronotum: Generally trapezoidal, convex, carinate, and sulcate. Wider than long, widest about 1/3 distance from base, narrowest at apex. Lateral margins entire, margined and faintly crenate, weakly sinuate; anterior margin smooth and shiny, arcuate over base of head, apicolateral angles acute; basal margin weakly sinuate, basolateral angles more or less right angled. Disc moderately convex with narrow, median, longitudinal carina extending from near apical margin to base; margined by two distinct subparallel, sublateral carinae extending from near apical margin to base, often obscured at basal 1/3–1/2 by deep, closely-spaced punctures; distance between sublateral carinae at apex less than head width. Sublateral carinae each bordered laterally at basal 1/3 by a shelf-like area extending nearly to lateral margin, area margined by an obscure to distinct carina; carinae together having an “h”-shaped, forked appearance. A deep, granulate sulcus at lateral margin, widest anteriorly, abruptly narrowed at basal 1/3; a pair of broad, shallow foveae present near basal margin, mesal to bases of main sublateral carinae. Disc of pronotum with small, sparse to moderately dense punctures accompanied by long, fine setae; basolateral shelf-like area rugose with deep, closely-spaced punctures. Elytron: Elongate, convex, laterally marginate; disk carinate and sulcate, depressed at base; together wider than base of pronotum. Lateral margin slightly arcuate to apical 1/4, then abruptly narrowed to rounded tip. Sublateral carinae at intervals 7 and 8, bordering striae 6 and 7, joined at the umbone; the more medial stria ends at about 1/5 the distance from the elytral apex, most distinct in apical 1/3; the more lateral stria is shorter. Longitudinal sulcus 3 intervals wide, extending from carina at interval 8 to lateral margin, deepest adjacent to metasternum. Nine punctate striae. Scutellum: Small, longer than wide. Metathoracic wings: Present or absent. Legs: Prothoracic leg shortest, metathoracic leg longest. Femur with basal patch of pale yellow setae on medial/inner surface, at basal 2/3 of profemur and metafemur and basal 1/2 of metafemur. Protibia with dense cleaning fringe of long, pale yellow setae on distal 2/3–3/4 of medial/inner surface; fringe of setae present but sparse on mesotibia and metatibia. Tarsus including claw nearly as long as tibia, with tarsomere 5 as long as tarsomeres 1–4 combined. Tarsal formula 5–5–5. Claws long and slender, without teeth. Venter: Glabrous medially, dense silver to golden plastron present laterally. Prosternal disc roughly triangular, emarginate; disc concave anteriorly, convex between procoxae, concave posteriorly near apex; anterior margin straight beneath head, apex bluntly rounded and inserted into a deep mesosternal fossa. Mesosternal disc concave between mesocoxae. Metasternal disc roughly cordate with a median, longitudinal sulcus, partly margined with a carina extending from between mesocoxae posteriorly nearly to metacoxae; each metacoxa with a small, posteriorly-projecting lobe. Abdomen with 5 sterna, most convex medially; sternum 1 with a pair of arcuate, divergent carinae extending from mesal margin of metacoxae to posterior margin of sternum, forming an approximate triangle; sternum 5 broadly triangular with a bluntly rounded apex. Plastron present on gena, gula, prosternal epimeron and hypomeron, metasternal episternum and lateral to carinae, elytral epipleura (hypomeron) except for base, laterally on all abdominal sterna, and on bases of all coxae. Genitalia ( Figs. 5–7 ): Typical for an elmine and with no features unique to the genus.

Adult Diagnosis. Adults of Bryelmis superficially resemble those of Cleptelmis , and can be mistaken for this genus because of basally forked sublateral pronotal carinae and similar size, shape, and coloration. Bryelmis is distinguished by a median longitudinal pronotal carina and distinct elytral sublateral carinae, and the often-indistinct forks of the sublateral pronotal carinae and basal areas between are more or less “h”-shaped. Cleptelmis lacks a median pronotal carina and elytral sublateral carinae, and the basal forks of the distinct sublateral pronotal carinae form an upside-down “Y.” The genera Rhizelmis Chandler and Ampumixis Sanderson both have a median pronotal carina like Bryelmis , but lack elytral carinae.

Bryelmis keys to Cleptelmis in White and Roughley (2008), couplet 11; Shepard (2002), couplet 11; and Brown (1972), couplet 46. To include Bryelmis , the following substitutions should be made:

# Pronotal carinae appearing forked at basal third................................................................ A

A Pronotum with median longitudinal carina, at least anteriorly; elytra with sublateral carinae... ........................................................... Bryelmis

A′ Pronotum without median longitudinal carina; elytra without sublateral elytral carinae........... ......................................................... Cleptelmis

I find the character “pronotal carinae forked at base or not forked at base” to be problematic and subject to misinterpretation, and think that existing generic keys need revision.

Larval Description. Mature larva ( Fig. 2 ) approximately 4.5 mm long, 0.7 mm wide at metathorax; elateriform, tapering posteriorly, subtriangular in cross-section; red brown with pale middorsal suture, head darker; moderately to densely tuberculate, with flattened setae. Head: Highly sclerotized, darker dorsally than ventrally, normally partly concealed by pronotum. Antenna cylindrical, 3-segmented; basal segment stout, as wide as long, 1/3 length of segment 2; segment 2 longest, 3X as long as wide, bearing apical seta as long as apical segment; apical segment minute, 1/2 width and 1/4 length of segment 2. Stemmata well-developed, grouped in an oval cluster. Frontal sutures together narrowly Ushaped and meeting near base of head, epicranial stem very short; frons dorsolaterally flattened. Clypeus fused to frons. Labrum transverse, 4X longer than wide, truncate with rounded apicolateral margins, margins setose. Mandible with 3 stout, blunt, apical teeth; the middle one largest. Maxilla with galea and lacinia distinct and apically setose; maxillary palpus transparent, 4-segmented, with a long seta laterally adjacent. Labium rectangular, 2X longer than wide; labial palpus transparent, 2-segmented. Thorax: Prothorax nearly as long as meso- and metathorax together, with 2 irregularlyshaped mesolateral depressions on each side; prosternum with cervical sclerites configured like a “V,” postpleurite with a single, undivided sclerite, posterior sternum absent (procoxal cavities open posteriorly). Mesothorax and metathorax of similar size and shape, with 2 anterolateral depressions; mesothorax with a pair of lateral, tuberculate spiracles; meso- and metasternum each with 2 pairs of pleural sclerites. Notal margins rounded laterally. Legs 5-segmented, terminal segment a tarsungulus. Abdomen: Nine-segmented; segments 1–7 with separate tergites, pleurites, and sternites; segments 8 and 9 each united into a ring. Pale middorsal suture on tergites 1–7; each tergite with a middorsal, humplike protuberance on posterior tergal margin becoming more prominent on posterior segments, together appearing bluntly saw-toothed in lateral view ( Fig. 2b ). Dorsal, anterolateral spiracles near margins of segments 1–8. All segments except 9 with apical fringe of peg-like setae. Segment 9 narrow, elongate, with emarginate apex; dorsal longitudinal carina convex in lateral view except near apex; tip acuminate in lateral view; ventral operculum ovate, broadly rounded anteriorly and narrowly rounded posteriorly; opercular chamber with 2 retractile anal hooks.

Larval Diagnosis. Bryelmis larvae ( Fig. 2 ) most resemble those of Ampumixis in general shape and sclerite characteristics. They differ in that Ampumixis has prominent dorsal clusters of pale, spatulate setae on the middorsal and mediolateral protuberances and lateral margins, whereas Bryelmis at most has small numbers of pale, flattened setae. In Ampumixis , all abdominal tergites have pronounced, rounded middorsal protuberances; in Bryelmis , they are less developed and usually most noticeable on the posterior segments. Although the larvae of Optioservus Sanderson and Heterlimnius Hinton are subtriangular in cross-section like Bryelmis , unlike Bryelmis ( Fig. 2c ) their prothoracic postpleurites are composed of two parts. In addition, the lateral margins of the thorax are explanate in the former genera, while those of Bryelmis are not. The larvae of Cleptelmis and Atractelmis are hemicylindrical and do not have dorsomedial hump-like protuberances.

Bryelmis larvae key to Ampumixis in White and Roughley (2008), couplet 18, and Brown (1972), couplet 26. To include Bryelmis , the following substitution should be made:

# Body robust and broad, subtriangular in cross section; with or without spatulate spines along lateral margins and middorsal line ................A

A With prominent clusters of spatulate spines along lateral margins and middorsal line.... Ampumixis

A′ Without prominent clusters of spatulate spines ........................................................... Bryelmis

Etymology. The generic name combines bry-, from the Greek bryon, meaning moss, plus elmis, from the nominate genus of the family, Elmis. Gender: feminine.

Figures

Fig. 1. Dorsal habitus of Bryelmis rivularis, type species.

Fig. 2. Larva of Bryelmis. a) Dorsal view, b) Lateral view, c) Sternum.

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

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.