Liocanthydrus Guignot, 1957

Baca, Stephen M., Gustafson, Grey T., Toledo, Mario & Miller, Kelly B., 2014, Revision of the Neotropical burrowing water beetle genus Liocanthydrus Guignot (Coleoptera: Noteridae: Noterinae: Noterini) with the description of two new species, Zootaxa 3793 (2), pp. 231-246 : 233-235

Liocanthydrus Guignot, 1957

Liocanthydrus Guignot (1957: 42) ; Nilsson (2011: 27–28); Gomez & K.B. Miller (2013: 2–3). Canthydrus (Liocanthydrus) Guignot (1957: 42) ; Nilsson (2005: 109) (cat.);

Siolius J. Balfour-Browne (1969: 5–6) ; Nilsson (2005: 124) (cat.); K.B. Miller (2009: 191–219); Nilsson (2011: 31) (cat.); Gomez & K.B. Miller (2013: 2–3). (new synonymy).

Type species. Canthydrus angustus Guignot, 1957 (by original designation)

Diagnosis. Distinguishable from other genera of Noterini by the following combination of characters: 1) prosternal process very broad and truncate with slight posteriomedial sutural projection ( Fig. 1 a); 2) anteroapical angle of metafemur with close, linear series of long setae ( Fig. 2 a); 3) pronotal margins smooth and pronotal bead broad ( Figs 10–15 ); 4) posterior metatibial spur smooth, not serrate ( Fig. 2 b); and 5) female genitalia bearing short laterotergites extending posteriorly beyond bases of gonocoxae (fig. 12 in K.B. Miller 2009).

Description. Medium sized beetles, TL = 2.7–3.35 mm; body form elongate, oval, weakly to moderately convex and posteriorly attenuate.

Color and appearance. Very shiny, elytra superficially iridescent. Pronotum and head color ranging from yellow to darker reddish brown; elytra brown to nearly black; most species with elytral maculae, usually produced as bands, sometimes reduced to spots, appearing similar in color to head and pronotum; pronotum with lateral margins darkened; some species with dark anteromedial maculation immediately posterior to head capsule; color of ventral surface ranging from brownish yellow to darker brownish red; color of legs and noterid platform similar to venter but darker.

Head. Eyes well developed, HW/EW = 1.47–1.73; frons with dense series of shallow, irregular punctures directly mediad of each eye, sometimes forming a small furrow; clypeus slightly convex, anterior margin subtruncate to truncate, somewhat expanded anteriorly nearly concealing labrum from above, with sparse submarginal series of shallow and finely setiferous punctures; frontoclypeal suture indistinct; labrum slightly convex, laterally rounded, distal margin truncate to very slightly arcuate. Maxillary palp length approximately 3/4 × width of labrum, ultimate palpomere elongate, nearly half of overall palp length, distally attenuate and apex rounded to truncate, emarginate with small sensory field. Labial palp length approximately 2/3 × width of labrum, ultimate palpomere subtriangular, bifid with sensory field along medioventral margin, with second smaller, round sensory field anteromedial of medial margin on protuberance; palp length greater than 2 × combined length of basal palpomeres. Antenna length approximately 4/5 × head width, antennomeres slightly serrate; antennomere XI about 2 × length of antennomere X, attenuate distally.

Thorax. Pronotum broad and convex; pronotal bead broad, ( Figs 10–15 ), width subequal to antennomere VII width anteriorly, attenuate to ca. 1/2 × antennomere VII width posteriorly, continuous around anterolateral angles, indistinct along anterior margin; series of fine setiferous punctures across entire width of pronotum adjacent to anterior margin. Elytra with sparse and fine punctations, many punctures bearing very fine setae; with indistinct series of such setiferous punctures present along entire basal margin, sparsely continued along lateral margins, serial punctures nearly indistinct; shallow reticulate microsculpture present. Ventral surface shiny, glabrous, with reticulate microsculpture produced as mesh of small isodiametric cells. Prosternum longitudinally broad anterior to procoxal cavities, narrowing laterally, with evenly spaced series of setae projecting anteriorly from anterior margin and few indistinct setae on discal surface; microsculpture fine, indistinct, slightly more impressed on prosternal process; anterior prosternal bead pronounced medially, becoming broad, flattened, and indistinct laterally; prosternal process very broad, posteriorly truncate with weak posteromedial projection ( Fig. 1 a); Metasternum raised and continuous with prosternal process ( Fig. 1 ); noterid platform extending posteriorly beyond first abdominal ventrite, with sharply rounded apical lobes bearing 2–5 stout, closely spaced setae, medial surface nearly glabrous, with few fine setiferous punctures, ventrolateral margins of platform with linear series of stout setae produced from strong punctures posterior to metasternum and extending to metacoxal lobes ( Fig. 1 ); microsculpture of metasternum and noterid platform fine, shallowly impressed; metacoxal plates with microsculpture distinct, cells enlarged. Profemur with 8–12 setae situated in short linear series on distal third of anteroventral margin. Protibia with large, curved spur near apex and oriented posteriorly; with distinct setal fringe arising medially along lateral margin, continuous at apex, absent on distal half of medial margin, with few swimming hairs near basolateral angle. Mesofemur base with setal field on anterior face, with two linear series of setae extending distally along anteroventral and anterodorsal margins, bearing 2 punctures with stout setae on ventral half of anterodistal margin. Metafemur ( Fig. 2 ) with series of 6–9 closely spaced setae in oblique line near anteroapical angle ( Fig. 2 a), nearly continuous with anteroventral series of finer setae; posterior metatibial spur smooth ( Fig. 2 b). Microsculpture nearly indistinct on femora, tarsi and protibia; meso and metatibiae with sculpture distinct, moderately impressed.

Abdomen. Ventral surface nearly glabrous, with nearly indistinct reticulate microsculpture; ventrites II and III fused, suture indistinct; ventrites IV and V similar in size; ventrite VI triangular, slightly carinate medially lateral margins of ventrites III–V each with 2–3 slender setae arising from punctures, situated in longitudinal series along lateral margin; ventrite 6 more setose, punctate near apex and laterad of median.

Males with protarsomeres not dilated; protarsomeres I–III each with one to two adhesive setae, four to five in total; protarsomeres IV and V slender, not bearing adhesive setae. Mesotarsomeres not dilated; mesotarsomeres I–II each with one to two adhesive setae, two to three in total. Aedeagus asymmetrical; median lobe ( Figs 16–22 ) curved dorsally, ventrally with deep longitudinal groove subtended by lateral flanges, left lateral flange enlarged, expanded ventrally, attenuate apically, and converging with right side at or near apex to create rounded or subcylindrical and attenuate lobe, base with processes comprised of small lateral notches and a medial hook-like projection where lateral lobes articulate; left lateral lobe ( Figs 16–22 ) sub-triangular to scalene in lateral aspect, shorter than to subequal in length to median lobe, distally with distinct continuous fringe of setae on medial surface, in some specimens with fringe slightly expanded at apex to form a small setal field, base with folded process; right lateral lobe ( Figs 16–22 ), ca. 2/3 or less × length of left lateral lobe, triangular to subtriangular, greatly expanded from base, without setae, with deep longitudinal groove on dorsal side, creating an inward fold.

Females nearly indistinguishable from males externally; slightly larger on average with protarsi and mesotarsi as in males, but without adhesive setae; female genitalia with gonocoxosternite broad, triangular; laterotergites shorter than to subequal in length to gonocoxae and extending posteriorly beyond gonocoxal base; gonocoxae scalene to subscalene in lateral aspect (fig. 12 in K.B. Miller 2009).

Biology. Collecting data indicate that Liocanthydrus can be found in several types of aquatic environments, but are most commonly found in lotic habitats or those associated with moving water such as pools near the bases of waterfalls. Examined specimens were most commonly collected from rivers, streams, creeks, or morichales, usually along the margins or in debris such as logs, leaf packs, or root mats. Relatively few individuals were collected in standing water habitats, such as detrital pools, and no specimens were collected from ponds. A very small number of specimens were taken at lights.

Figures

FIGURES 1, 2. Diagnostic characters of Liocanthydrus: 1) L. bicolor, prosternum, metasternum and metacoxae, ventral aspect; 1 a) prosternal process; 2) L. nanops sp. n., metaleg, anterior aspect; 2 a) series of setae on anteroapical angle of metafemur; 2 b) posterior metatibial spur.

FIGURES 10 – 15. Liocanthydrus species, lateral aspect: 10) L. angustus; 11) L. uniformis; 12) L. bicolor; 13) L. armulatus sp. n.; 14) L. clayae; 15) L. nanops sp. n. Scale bar = 1.0 mm.

FIGURES 16 – 22. Aedeagi of Liocanthydrus species. a) median lobe, right lateral aspect; b) median lobe, dorsal aspect; c) median lobe, left lateral aspect; d) left lateral lobe, right lateral aspect; e) right lateral lobe, left lateral aspect: 16) L. angustus; 17) L. uniformis; 18) L. bicolor; 19) L. armulatus sp. n.; 20) L. clayae; 21) L. nanops sp. n.; 22) L. octoguttatus. Scale bars = 0.2 mm. Notes: Terminology follows K. B. Miller & Nilsson (2003). Illustrations of lateral lobes depict medial (inner) surfaces.