Stetholus elongatus Carter & Zeck, 1929

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 elongatus Carter & Zeck, 1929

Figs 9 , 36 , 37

Type locality.

Allyn River at Gresford; 32.350°S, 151.750°E; New South Wales, Australia (holotype deposited in the Australian Museum, Sydney).

Paratypes examined

(5). Gresford / Allyn R., N.S.W. / Oct. 1926 / H. J. Carter // PARATYPE [blue label] (4 ANIC, 1 SAMA).

Other material examined

(56). Australian Capital Territory. Kambah Pool / Murrumbidgee / River ACT / 1.i.1978 / J.F.Lawrence (3 ANIC); AUSTRALIA: ACT / Murrumbidgee River / Point Hut Xing S Canberra / 35°33'55"S, 149°03'56"E / 1-I-2001, coll. C. B. Barr (9 EMEC, 3 QM); AUSTRALIA: ACT / Murrumbidgee River at / Casuarina , E Cotter Dam / 35°19'41"S, 148°57'01"E / 2-I-2001, coll. C. B. Barr (4 ANIC, 9 EMEC, 3 QM); AUSTRALIA: ACT / Gigerbine [Gigerline] NR, Angle / Crossing 31 XII 2000 / Murrumbidgee River (WDS-A-1337 on reverse)// William D. / Shepard, leg. (3 EMEC). New South Wales. AUSTRALIA: NSW / Deua NP, Deua River at / Deua River Campground / 35°45'00"S, 149°54'53"E / 4-I-2001, coll. C. B. Barr (8 EMEC); AUSTRALIA: NSW / Deua NP, Deua R / Cmpgd. 4 I 2001 / Deua River (WDS-A-1348 on reverse) // William D. / Shepard, leg. (3 EMEC); Tallong / N.S.W. / FHTaylor (2 ANIC, 4 SAMA); same locality // On submerged / sticks in the / Shoalhaven R. (2 ANIC); AUSTRALIA: NSW / NW of Braidwood / 3 I 2001 / Shoalhaven River (WDS-A-1344 on reverse) // William D. / Shepard, leg. (2 EMEC); Pierce’s Pass, / Blue Mtns., N.S.W. / 5.xii.1971 / G.B.Monteith (1 QM) .

Differential diagnosis

(n = 61). Stetholus elongatus (Figs 36 , 37 ) can be distinguished from other species of Stetholus (Figs 34-35 , 38 - 42 ) by a combination of the following characters: Antennae distinctly clavate; pronotum moderately sculptured, lacking basal sublateral carinae; metatibia usually with a narrow, elongate bare area of variable length at the posterobasal 1/3; male genitalia (Fig. 37 ) stout and heavily sclerotized. Stetholus woronora (Fig. 41 ) most closely resembles S. elongatus but has short, basal sublateral pronotal carinae. Although the male genitalia of the two species are similarly stout and heavily sclerotized, the penis of S. elongatus (Fig. 37 ) is narrow and tapered at the apex, while that of S. woronora (Fig. 42 ) is wide and bulbous near the apex. Stetholus longipennis (Figs 38 ) is usually shorter than S. elongatus (Fig. 36 ) (4.1-4.6 mm long vs. 4.7-5.3 mm, excluding the head), has slender, elongate antennae, and the male genitalia are strikingly different (Figs 39 , 37 ).

Variation.

The examined females exhibit minor secondary sexual dimorphism with the lateral margin of the elytra slightly explanate at the posterior 1/4 laterad to stria 11; in males, stria 11 is just inside the lateral margin, which is not explanate. The metatibia of both sexes has a posterior, linear bare patch which varies in length but is restricted to the basal 1/2, and nearly always the basal 1/3. This character is occasionally obscure, and is probably the result of abrasion of the setae. Otherwise, except for minor differences in the depth and extent of the pronotal impressions, the specimens examined are quite uniform. Measured specimens vary in size from 4.7-5.3 mm long and 1.8-2.1 mm wide (n = 12). The males and the females are of similar size: males 5.0-5.1 mm long, 1.8-2.1 mm wide (n = 7); females 4.7-5.3 mm long, 1.8-2.1 mm wide (n = 5). Carter & Zeck (1929) reported a body length of 5.0-6.0 mm in their species description which likely included the length of the head.

Distribution.

Stetholus elongatus occurs in the Australian Capital Territory, New South Wales, and Victoria (A.Glaister, in litt.), Australia (Fig. 9 ).

Habitat and behavior.

The habitat and behavior of this species is as described for the genus. Populations can be enormous in suitable habitats. Specimens also have been collected in light traps (A.Glaister, in litt.).

Associated byrrhoid taxa.

Elmidae : Larainae : Hydora laticeps , Ovolara australis ; Elminae : Austrolimnius spp., Coxelmis novemnotata , Kingolus metallicus , K. tinctus , K. spp., Notriolus maculatus , N. minor , N. setosus , N. spp., Simsonia spp. Psephenidae : Sclerocyphon basicollis , S. minimus , S. striatus .

Comments.

As noted in the Hydora laticeps Comments, there are specimens of S. elongatus in the>AM, NMV and SAMA which bear locality labels identical to those of H. laticeps . Carter & Zeck (1929, 1932) made no mention of the S. elongatus specimens from Tallong, or that the two species co-occur. The larva of this species has been reared to the adult by Glaister (A.Glaister, in litt.).

Figures

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 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 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 38, 39. Stetholus longipennis sp. nov., male 38 habitus, 4.2 mm long A dorsal B ventral 39 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.