Stetholus carinatus, Barr & Shepard, 2021

Barr, Cheryl B. & Shepard, William D., 2021, A review of the Larainae of Australia with description of seven new species and the new genus Australara (Coleoptera, Byrrhoidea, Elmidae), ZooKeys 1073, pp. 55-117 : 55

Stetholus carinatus sp. nov.

Figs 8 , 34 , 35

Type locality.

Upper North Creek, Mt. Elliot, Bowling Green Bay National Park southeast of Townsville; 19.490° S, 146.974° E; north Queensland, Australia.

Type material.

Holotype male. "Mt Elliot NP, N.E.QLD / (Upper North Ck, 1000m) / 3-5 Dec 1986 / Monteith, Thompson&Hamlet / Flight intercept trap // HOLOTYPE / Stetholus / Stetholus carinatus / Barr & Shepard" [red label, handwritten]. Dry pinned. Deposited in the Queensland Museum, South Brisbane; Registration Number QM T250616.

Differential diagnosis.

The single male specimen of S. carinatus (Figs 34 , 35 ) is characterized by the following: shorter (3.7 mm) than other Stetholus species (3.9 mm or longer) (Figs 36 - 42 ); pronotum with a pair of distinct, long, basal sublateral carinae; elytron with a short, faint, accessory basal stria with a few punctures between striae 1 and 2; mesotibiae with posterior surfaces glabrous and shiny, metatibiae entirely setose; male genitalia unique (Fig. 35 ) (those of S. metatibialis are unknown). The species is separated from all other Stetholus except S. metatibialis (Fig. 40 ), which it most closely resembles, by the long, basal sublateral pronotal carinae. Stetholus carinatus differs from S. metatibialis as follows: length shorter (3.7 mm vs. 3.9 mm); metatibiae entirely setose; elytron with accessory stria obscure.

Description

(n = 1). Holotype male. Body: Size 3.7 mm long, 1.4 mm wide; elongate, ~ 2 × longer than wide. Dorsal color dark brown; head black; first two antennomeres, palpi, venter, coxae, trochanters, femora yellow or yellow-brown. Short yellow setae on all surfaces. Head: Densely and finely punctate, punctures <1 diameter apart or nearly contiguous; densely setose. Vertex with a faint V-shaped impression, open anteriorly, extending from antennal bases towards occiput; frontoclypeal suture arcuate. Antenna with eleven antennomeres; antennomeres 1 and 2 yellow-brown with long, coarse, dark setae; antennomere 1 longest, ~ 3 × longer than wide, curved; antennomere 2 spherical; antennomeres 3-11 brown with dense yellow setae, subserrate, together forming an elongate club; antennomeres 7-11 of equal width, antennomere 11 short with bluntly rounded apex. Eye finely faceted, suboval at base, not protuberant; fringe of long, curved, black setae at dorsal margin. Clypeus convex, broadly rectangular, weakly emarginate; disc densely setose, anterior and lateral margins with long setal fringe. Labrum rectangular, longer and slightly narrower than clypeus; setose; anterior margin emarginate with a band of short, yellow setae; lateral margins with dense fringes of long, yellow setae, each margin with a discrete tuft of longer, darker, curved setae (setal origin unclear, possibly mandibular). Maxillary palpus yellow, with four setose, palpomeres; palpomere 1 short, annular; palpomere 2 twice as long as wide; palpomere 3 nearly as long as 2, wider apically; palpomere 4 wide, ovoid, ventral surface with a broadly oval, slightly concave, white sensory area angled obliquely from the apex to the base. Labial palpus yellow, glabrous, with three palpomeres; palpomeres 1 and 2 short, annular; palpomere 3 broadest, apex truncate with a narrowly oval, flat, white sensory area. P ronotum: Shape generally trapezoidal, wider than long, widest at base; 0.9 mm long, 1.1 mm wide; disc densely punctate, punctures spaced <1 diameter apart. Anterior margin arcuate; anterior angles obsolete; lateral margins weakly sinuate, moderately explanate at basal 2/3; posterior angles 90°, sharp, widely excavated; posterior margin weakly trisinuate. Disc weakly convex with a shallow, transverse V-shaped impression at apical 1/3; two basal, sublateral carinae 1/3-1/2 as long as pronotum, bordered by impressions, medial impressions shallow, elongate; two small, shallow prescutellar foveae. Scutellar shield: Longer than wide, apex rounded; flat; densely setose. Elytron: 2.8 mm long, 0.7 mm wide. Elytra conjointly 2 × as long as wide; anterior 2/3 parallel-sided; posterior 1/3 widest; lateral margins narrowly marginate. Humerus inflated, elytral base depressed medially; disc weakly convex at anterior 1/4 then flattened. Disc with ten punctate, weakly impressed striae, intervals flat; accessory basal stria between striae 1 and 2 short, faint, with few punctures; punctures of striae 2 and 3 very small and obscure near base; striae 3 and 4 join near apex; disc punctures mostly separated by one diameter, smaller apically. Metathoracic wings: Macropterous. Prosternum: Very short anterior to procoxae. Prosternal process very narrow, long, 4 × longer than wide; parallel-sided posterior to coxae; apex narrowly rounded; surface tomentose. Mesoventrite: Short, very setose, with a deep mesoventral cavity to receive prosternal process. Metaventrite: Broadly rectangular; very setose; posterior 1/2-2/3 with a moderately wide, shallow, median depression, laterally convex; discrimen extending almost from anterior to posterior margin, narrowly incised at posterior 1/2; metakatepisternal suture distinct; disc laterally with shallow, closely spaced punctures; medially punctures mostly obscured by a broad, triangular patch of long, dense, recumbent, yellow setae. Legs: Of similar lengths; each leg with femur and tibia subequal in length; tarsus with tarsomere 5 longer than tarsomeres 1-4 combined; claws simple, long, sharply acute. Coxae yellow, metacoxae deeply sulcate; femora yellow, dorsal surfaces of each with a narrow brown stripe, apices brown; tibiae brown, each with a pair of spines at ventral apex, mesotibiae with posterior surfaces flat, yellow-brown, glabrous, shiny; tarsi yellow-brown. Abdomen: Five ventrites; ventrite 1 longest, ventrite 4 shortest, ventrites 2, 3, and 5 subequal in length; ventrites 1-3 weakly flattened at midline, ventrites 4 and 5 convex; ventrite 1 with a margined, triangular, intercoxal projection; ventrites 2-4 with lateral margins each produced to form a small, rounded lobe which clasps the epipleuron; ventrites 4 and 5 with moderately deep impressions at anterolateral margins; ventrite 5 apex broadly rounded. Ventrites covered with shallow, closely spaced punctures; ventrite 1 with punctures more widely spaced, ventrites 2-5 with punctures more closely spaced; medial punctures mostly obscured by dense covering of yellow setae, longest at median 1/5 of ventrites 3-5. Aedeagus: Phallobase much shorter than parameres, penis slightly longer than parameres (Fig. 35 ). Parameres, in dorsal view (Fig. 35A ), widest basally; lateral margins weakly arcuate at basal 2/3, then parallel at apical 1/3; median margins straight and moderately divergent at basal 1/2, then arcuate to abruptly narrowed, strongly produced tips at apical 1/3; apices narrow, acute. Penis evenly convergent at basal 3/4, then abruptly narrowed at apical 1/4, apex very narrowly rounded; no visible corona; basal apophyses moderately long, 1/2 as long as phallobase, straight, very broad, blunt at tips. In lateral view (Fig. 35B ), penis bent and abruptly angled above parameres near midpoint. Fibula absent.

Etymology.

The specific epithet carinatus, an adjective in the nominative singular derived from the Latin meaning keeled, refers to the presence of a pair of basal, sublateral carinae on the pronotum.

Distribution.

North Queensland, Australia. Known only from the type locality on the north slope of Mt. Elliot (Fig. 8 ).

Habitat.

Geoff Monteith, one of the collectors, described the area thus: "Mt. Elliot is a high, isolated, rainforest-capped mountain with a strikingly unique and endemic fauna" (G. Monteith, in litt.). The specimen was collected using a flight intercept trap at 1000 m elevation.

Figures

Figure 40. Stetholus metatibialis sp. nov., holotype female, 3.9 mm long A dorsal habitus B ventral habitus C head, frontal view D head, ventral view.

Figures 1 - 12. Geographical distribution of species records 1 Australara glaisteri gen. nov., sp. nov. 2 Hydora laticeps 3 Ovolara australis 4 Ovolara lawrencei sp. nov. 5 Ovolara leai 6 Ovolara monteithi sp. nov. 7 Potamophilinus papuanus 8 Stetholus carinatus sp. nov. 9 Stetholus elongatus 10 Stetholus longipennis sp. nov. 11 Stetholus metatibialis sp. nov. 12 Stetholus woronora sp. nov.

Figures 34, 35. Stetholus carinatus sp. nov., holotype male 34 habitus, 3.7 mm long A dorsal B ventral 35 male genitalia A dorsal view B lateral view C ventral view.

Figures 36, 37. Stetholus elongatus 36 female habitus, 5.2 mm long A dorsal B ventral 37 male genitalia A dorsal view B lateral view C ventral view.

Figures 41, 42. Stetholus woronora sp. nov., holotype male 41 habitus, 5.2 mm long A dorsal B ventral 42 male genitalia A dorsal view B lateral view C ventral view.