Hexanchorus homaeotarsoides, Maier, Crystal A., 2013

Maier, Crystal A., 2013, A revision of the Larainae (Coleoptera, Elmidae) of Venezuela, with description of nine new species, ZooKeys 329, pp. 33-91 : 51-54

Hexanchorus homaeotarsoides sp. n. Figs 3, 37, 38, 39, 40, 41, 42

Type material.

Holotype Male."Venezuela; Amazonas; P.N. Duida; Marahuaka" "Cabeceras del; Rio Yameduaca; 3°38'N, 65°28'W; 1-3-II-92, 1230m" "Exp. Terramar; J. Clavijo; A. Chacon" Holotype deposited in MIZA. Paratypes (12): VENEZUELA: Amazonas State: Same data as holotype (12 specimens MIZA). Paratypes will be deposited in: 7 in MIZA, 1 in MALUZ, 1 in USNM, 2 in SEMC.

Diagnosis.

Hexanchorus homaeotarsoides is distinctive in the genus, as it is one of only two species to possess a median projection on the third abdominal ventrite of the female. It differs from the only other species which bears this character, Hexanchorus inflatus , by its evenly rounded elytra and aedeagus with a saw tooth apex. Additionally, the antennae are short, not extending behind transverse impression of pronotum; and the pronotum has a strong median longitudinal impression and the apical third of the elytra are not inflated posteriorly.

Description.

Holotype Male. Body elongate, subparallel, dorsum moderately convex. Length, 4.2 mm; greatest width, 1.5 mm. Body dark brown dorsally (Fig. 37); venter dark brownish black (Fig. 38). Base of antenna light to medium brown. Dorsal surface densely covered with short recumbent setae; ventral surface densely covered with dense, short, recumbent setae. Setae lacking greenish iridescence (Fig. 38). Surface microreticulate, with dense fine punctures; fine punctures separated by distance equal to puncture diameter.

Head moderately coarsely, densely punctate; punctures separated by their diameter; cuticle microreticulate. Clypeus with anterior margin straight; angle on each side square. Labrum with anterior margin entire and gently rounded; angle on each side obtuse, covered with setae approximately twice as long as setae on head. Eyes hemispherical, narrowed posteriorly and bordered by long black curved setae ( “eyelashes”) that arise near dorsal and ventral sides of eyes and extend toward middle of eye, setae not as prominent as in other species. Antenna pubescent, clubbed; basal antennomeres I and II medium to light brown, with dense recumbent setae and dense brushy light brown setae, lacking long setae (Fig. 39). Antennal club very loose, just slightly thickened towards apex. Antennae short, reaching transverse groove of pronotum. Apical antennomeres dark brownish black, with dense recumbent setae. Apical antennomere rounded.

Pronotum 1.1 mm long, 1.0 mm wide; with strong sublateral groove (Fig. 41); lateral margins slightly sinuate; anterolateral angles square, not explanate; base of pronotum slightly sinuate and with broad lobe medially; posterolateral angles obtuse, slightly explanate, declivous, depressed adjacent to each angle (Fig. 41); discal area with fine, dense punctures, punctures separated by a distance equal to or less than their diameter; cuticle microreticulate. Pronotal disc with strong median longitudinal depression, with strong postero-medial impression (Fig. 41); disc covered with short, dense setae. Lateral projection of hypomeron truncate. Prosternum short in front of procoxae; without tuft of dense golden setae apicomedially (Fig. 38). Prosternal process broadly triangular, broad at base and slightly tapering to apex; disc slightly impressed, without V-shaped groove; lateral margins reflexed; middle flattened; apex broadly, acuminate (Fig. 38). Scutellum slightly longer than broad, strongly convex, distinctly elevated above the adjacent elytral intervals. Mesoventrite short, depressed, with a deep, broad, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc inflated on posterior three-fourths, finely punctate behind mesocoxae, punctures becoming more sparse laterally, with large, rounded depressions scattered on disc; with shallow longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with short, dense pubescence; cuticular surface of metaventrite finely microreticulate.

Legs long and slender, dark brown. Procoxae and metacoxae moderately widely separated; mesocoxae slightly more widely separated. Protibia lacking excavation for reception of tarsi, lacking apical tooth. Protarsus of male expanded apicomedially. Mesotibiae of male with medial pubescent area long; lateral pubescent area only at extreme base; with fine, short, nearly longitudinal carina on inner apex. Tarsal claws long and stout, light brown. Metafemur of male with internal glabrous patch.

Elytron with ten rows of fine punctures; punctures separated by a distance three to four times the diameter of the puncture; intervals with short, dense pubescence; humeral area swollen (Fig. 37). Elytral striae visible apically. Elytron widening to about posterior two-thirds before converging to rounded apex (Fig. 37). Apical third of elytron not, or just barely inflated. Elytron without strong impression at basal third. Lateral bead of elytron strongly sinuate. Elytra 3.5 times as long as pronotum; broadest point across humeri. Inner side of apex angled; lateral margins smooth; humeri gibbous; elytral intervals slightly elevated; punctures on intervals no larger than finest punctures of head and pronotum and separated by 2-5 times puncture diameter.

Abdomen with five ventrites. First three ventrites broadly, shallowly depressed and distinctly carinate adjacent to metacoxae; carinae extending longitudinally behind metacoxae for almost entire length of first ventrite; cuticle densely covered with short, recumbent setae. Last ventrite deeply and broadly emarginate. Aedeagus unique in configuration, acute, with row of small teeth at apex; parameres long, extending past halfway up aedeagus (Fig. 42).

Female. Externally similar to male, except inner apex of each elytron acute and slightly turned upward (Fig. 37). Protibiae slightly less curved than those of male. Mesotibiae without carina on inner apex. Metaventral disc not as deeply and less extensively concave. Abdominal sterna 1-3 convex, not concave; apicomedial margin of third ventrite with distinct posterior projection (Fig. 40).

Intraspecific variation.

This species varies slightly in color, length (4.1-5.1 mm), and degree of setation.

Etymology.

The specific epithet, “homaeotarsoides” is a reference to the third ventrite of the female, which bears resemblance to the abdominal ventrite 4 of the male in the rove beetle ( Staphylinidae ) genus Homaeotarsus .

Distribution and habitat.

This species is known only from the type locality at Rio Yameduaca in Amazonas State, Venezuela (Fig. 3). Nothing is known about its habits and exact microhabitat preferences.

Associated species.

Hexanchorus inflatus sp. n.occurs in the same region of Venezuela, but no other species of laraine elmid has been collected at this locality.