Pleuroseta wentworthi ( Richards, 1973 )

Kuwahara, Gregory K. & Marshall, Stephen A., 2023, A revision of the Australian genus Pleuroseta Richards (Diptera, Sphaeroceridae), European Journal of Taxonomy 910, pp. 69-97 : 91-96

Pleuroseta wentworthi ( Richards, 1973)

Figs 5C , 12–15 , 16C

Leptocera (Biroina) dorrigonis Richards 1973: 333 , figs 30, 44–45. Syn. nov.

Leptocera (Pleuroseta) wentworthi Richards 1973: 355 .

Biroina dorrigonis – Marshall 1989: 602. — Roháček et al. 2001: 125.

Pleuroseta wentworthi – Marshall 1989: 605. — Roháček et al. 2001: 199.

Pleuroseta dorrigonis – Kuwahara & Marshall 2022: 10 .

Type material

Holotype of Leptocera (Pleuroseta) wentworthi

AUSTRALIA • ♂; New South Wales, Blue Mountains, Wentworth Falls ; 20 Nov. 1958; D.K. McAlpine leg.; AMSA K.70475 .

Holotype of Leptocera (Biroina) dorrigonis

AUSTRALIA • ♂; New South Wales, Dorrigo National Park ; 30 Mar. 1960; D.K. McAlpine leg.; AMSA.

Paratypes of Leptocera (Biroina) dorrigonis (specimen in BMNH examined by SM in 1989) AUSTRALIA – New South Wales • 1 ♀; Kangaroo Valley ; 23 Mar. 1961; D.H. Colless leg.; ANIC • 1 ♂; National Park ; 28 Apr. 1956; D.K. McAlpine leg.; AMSA • 1 ♀; Otford ; 26 Jan. 1959; D.K. McAlpine leg.; AMSA. – Queensland • 1 ♂; Mount Glorious, near Brisbane ; 4 Jan. 1961; D.K. McAlpine leg.; BMNH .

Other material examined

AUSTRALIA – New South Wales • 1 ♂; 8 km NW of Bruxner Park ; 16 Apr. 1970; D.H. Colless leg.; ANIC • 1 ♂; 11 km NE of Bulahdelah, O’ Sullivans Gap Reserve ; 11 Jun.–27 Aug. 1982; S. Peck leg.; sclerophyll, flight-intercept trap; DEBU • 1 ♂; Crescent Head, Delicate Knobby, ForRest Cottage ; 31°15'53" S, 152°57'43'' E; 25 Mar. 2019; S.A. Marshall leg.; lower forest , dung; DEBU • 3 ♂♂, 1 ♀; Richmond Range State Forest ; 28°28'48'' S, 152°35'24'' E; 600 m a.s.l.; 13–14 Feb. 1983; T. Weir and A. Calder leg.; human dung trap; ANIC • 7 ♂♂; Ulong, Ashton’s Eco Retreat ; 30°13'47'' S, 152°55'12'' E; 22 Mar. 2019; S.A. Marshall leg.; dung; DEBU • 1 ♀; Upper Allyn River ; 2 Apr. 1970; D.H. Colless; ANIC . – Queensland • 2 ♂♂, 5 ♀♀; Mount Glorious ; 27°19'54'' S, 152°45'29'' E; 3–9 Jan. 1998; T. Hiller leg.; Malaise trap; DEBU .

Description

BODY ( Fig. 12A ). As described for P. ingens sp. nov. except as follows: length 2.7–3.4 mm. Frontal width 2.2–2.3 ×interfrontal height. Interfrontal bristles in three large subequal pairs surmounting a smaller pair. Gena with 10–14 setulae. Palpus with 3–4 ventral setae. Eye height 1.5–1.7× genal height. First postsutural pair of dorsocentral bristles separated by 7–9 rows of fine acrostichal setulae. Anepisternum with posterodorsal patch of 5–6 setae and 9–12 setulae. Legs brown and yellow, femora with preapical yellow ring, basal half to two-thirds of tibiae yellow but not in distinct bands (more gradual colour transition); tarsi yellow. Wing pattern ( Fig. 16C ) less distinct than in P. ingens . CS2 1.4×length of CS3.

MALE ABDOMEN ( Figs 5C , 12B–C , 13 ). S5 broad, uniformly setose laterally with large posteromedial desclerotized area, posterolaterally flanked by small rounded lobed with slightly enlarged setae. S6+7 complex: S6 with large (about as wide as desclerotized area of S5), dark, M-shaped ventral expansion situated under (dorsal to) emargination of S5; posterior to this lies a weakly sclerotized, cup-shaped central sclerite; S7 with elongate dextral extension reaching across to ring sclerite; S8 with dorsal, anteromedial semicircular emargination; ring sclerite weakly developed and partially fused to (and oriented perpendicular to) right side of S5. Epandrium distinctly bulging on right side; cercus indistinct from epandrium, with several long setae; subepandrial sclerite somewhat X-shaped, with much thicker dorsal arms and longer, thin ventral arms. Hypandrium triangular, anteromedial apodeme curved upwards anteriorly. Surstylus bilobed: anterior lobe hatchet-shaped with small posteroventral lobe and several basal setulae; posterior lobe triangular with many long setae. Postgonites small but elongate, triangular, slightly sinuate with small, triangular, preapical lobe. Phallapodeme elongate and curved; basiphallus large, V-shaped in lateral view, and laterally compressed. Distiphallus large (~7% total body length), divided into basal and apical sections: basal section sclerotized, tubular, and elbowed in apical third; apical section composed of a flattened, scoop-like lower sclerite and a pair of broad, curved lateral sclerites, together supporting largely membranous apex.

FEMALE ABDOMEN ( Fig. 14 ). Postabdomen stout, segments 6–8 partially fitting into segment 5 at rest; when fully everted, postabdomen comprising ~25% of total abdominal length. T6 and S6–7 broad with 8–12 posterior setae, sternites also with posteromedial patch of 2–4 small setae. T7 split medially into pair of rectangular plates, each with 3–4 posterior setae. T8 divided into two tall, curved, posteriorly long-setose, lateral plates. Epiproct shield-like, medially desclerotized with pair of dorsal setae. Cercus small, ovoid with an inner apical notch and 6–8 long, sinuate setae. S8 largely desclerotized, densely microtomentose, posteromedially emarginate, each lateral lobe sclerotized and bearing large seta and several smaller setae. Hypoproct broad, posteromedially triangular with two setae, 7–8 setulae, and dense microtomentum in posterior third. Spermathecae elongate, pear-shaped and lightly grooved with elongate, subconical, slightly curved stem.

Distribution

Australasian/Oceanian: Australia (NSW, QLD).

Remarks

The holotypes of Leptocera (Pleuroseta) wentworthi ( Fig. 15A ) and Leptocera (Biroina) dorrigonis ( Fig. 15B ) show no significant differences in externally visible characters, and Richards’ (1973) descriptions of either of these species could be equally applied to the other. Richards emphasized the characteristic patch of anepisternal setae in his description of his monobasic subgenus Pleuroseta , stating “R

2+3 is less sinuate and the prosternum is linear. From [ Biroina and Poecilosomella ] it differs in having a patch of about six bristles, three moderately large, near the hind margin of the mesepisternum [anepisternum], a character unique in the family”. Richards made no mention of anepisternal setae in his description of L. (B.) dorrigonis as part of his diverse subgenus Biroina (now Howickia ), but the anepisternal setae of that species are identical to those described for Pleuroseta wentworthi and the wing venation of both species is the same. Richards describes the wing of Pleuroseta as “dark with ill-defined pale spots” and the wing of “ Biroina ” dorrigonis as “brownish with about 6 not sharply defined whitish spots” but the wings of the type specimens of these two species are identical. It seems probable that Richards overlooked the anepisternal setae on the type specimens of P. dorrigonis and therefore failed to compare his “ Biroina ” dorrigonis to the genus Pleuroseta . We here treat P. dorrigonis as a junior synonym of P. wentworthi , with the caveat that the unique male type of P. wentworthi has not been dissected to confirm this synonymy by comparison of the male internal genitalia.

While Leptocera (Biroina) dorrigonis was published earlier in the same paper as Leptocera (Pleuroseta) wentworthi , we are acting as first reviser here to treat P. wentworthi as the senior synonym because it is the type species of the genus Pleuroseta .

Pleuroseta wentworthi resembles P. ingens sp. nov. and P. monteithi sp. nov. but differs by the yellow basal two-thirds of the fore tibia, three pairs of large interfrontal bristles, smaller male genitalia (the epandrium is much smaller than the head), and unmodified female epiproct.

Discussion

Prior to this revision, the Australian genus Pleuroseta was known only from the holotype of P. wentworthi and four type specimens of Leptocera (Biroina) dorrigonis , here recognized as a synonym of P. wentworthi . Pleuroseta now includes four species, bringing the total number of described Australian sphaerocerids to 105 species in 27 genera, of which 61 are endemic. Although Pleuroseta is currently known only from New South Wales, Queensland, and Western Australia. we have seen very few sphaerocerid specimens from states other than New South Wales, Queensland, Tasmania, and Western Australia, and the sphaerocerid fauna of New Guinea remains largely unknown.

Figures

Fig. 5. A. Pleuroseta occidentalis sp. nov. paratype, left wing, ventral view (debu00244165). B. Pleuroseta occidentalis paratype, hypandrium, dorsal view (debu00245797). C. Pleuroseta wentworthi (Richards, 1973), hypandrium, dorsal view (debu00264733). D. Pleuroseta ingens sp. nov. paratype, hypandrium, dorsal view (debu00160984). E. Pleuroseta monteithi sp. nov. paratype, hypandrium, dorsal view (debu00160892). Scale bars: A=0.50 mm, B–E=0.10 mm.

Fig. 12. Pleuroseta wentworthi (Richards, 1973).A. Male habitus, lateral view (debu00403539).B. Male terminalia, lateral view (debu00264733). C. Male terminalia, posterolateral view (debu00264733). Abbreviations: epa =epandrium; hyp=hypandrium; se = subepandrial sclerite; ss =surstylus. Scale bars: A =1.0 mm; B–C =0.30 mm.

Fig. 13. Pleuroseta wentworthi (Richards, 1973) (debu00264733). A. Aedeagus and associated structures, lateral view. B. Male S5–8, ventral view. Abbreviations: bp = basiphallus; dp =distiphallus; ea= ejaculatory apodeme; pg =postgonite; phal=phallapodeme. Scale bars: A–B =0.30 mm.

Fig. 14. Pleuroseta wentworthi (Richards, 1973) (debu00264635). A. Female terminalia, dorsal view. B. Female terminalia, ventral view. C. Spermathecae. Abbreviations: cer =cercus; epi =epiproct; hyp =hypoproct. Scale bars: A–B = 0.40 mm; C = 0.06 mm.

Fig. 15. A. Pleuroseta wentworthi (Richards, 1973) holotype, ♂, habitus, lateral view. B. Pleuroseta dorrigonis (Richards, 1973) holotype, ♂, habitus, lateral view. Scale bar: A–B =1.0 mm. Photo credit: N. Tees and R. Cox (AMSA).

Fig. 16. Pleuroseta left wings, ventral view. A. Pleuroseta ingens sp. nov. paratype (debu00162128). B. Pleuroseta monteithi sp. nov. paratype (debu00160892). C. Pleuroseta wentworthi (Richards, 1973) (debu402972). Scale bar: A–C= 0.5 mm.