Pleuroseta occidentalis Kuwahara & Marshall 2023, sp. nov.
Creators: name: Kuwahara, Gregory K.
name: Marshall, Stephen A.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Sphaeroceridae
Pleuroseta
Pleuroseta occidentalis

description: Pleuroseta occidentalis sp. nov.
urn:lsid:zoobank.org:act: 192B03A5-5FF7-411C-ACFB-564BA8CBF212
Figs 2–4, 5A–B
Etymology
The species name (from the Latin, occidentalis’, ‘western’) refers to the apparent restriction of P. occidentalis sp. nov. to Western Australia.
Material examined
Holotype
AUSTRALIA • ♂; Western Australia, Fernhook Falls, ~ 30 km north of Walpole, Deep River shoreline; 26–27 Nov. 2003; S.A. Marshall leg.; dung pans; WAM debu00244195.
Paratypes
AUSTRALIA – Western Australia • 5 ♂♂, 1 ♀; same collection data as for holotype; WAM • 5 ♂♂, 2 ♀♀; 15 km E of Walpole; 28–30 Nov. 2003; S.A. Marshall leg.; tingle tree forest, dung pans in leaf litter; WAM • 1 ♂; Boranup Forest, ~ 25 km N of Augusta; 34°09'52'' S, 115°04'34'' E; 19–20 Nov. 2003; S.A. Marshall leg.; karri forest; DEBU • 1 ♂; Mount Frankland, ~ 30 km N of Walpole; 26 Nov. 2003; S.A. Marshall leg.; pans; DEBU • 1 ♀; Peaceful Bay, Ficifolia Road and Nut Road; 28–30 Nov. 2003; S.A. Marshall leg.; dry heath, pans; DEBU • 6 ♂♂, 4 ♀♀; Porongurup National Park, Bolganup Creek; 8–16 Jun. 1980; S. and J. Peck leg.; DEBU • 7 ♂♂, 5 ♀♀; same collection data as for preceding; WAM • 3 ♂♂, 3 ♀♀; Wrenwood Cottages, 10 km N of Augusta; 34°15' S, 115°01' E; 20–23 Nov. 2003; S.A. Marshall leg.; paperbark grove, pans; DEBU.
Description
BODY (Fig. 2A). Length 1.8–2.3 mm. Head dark brown, lower portion of frons orange, antennae brown. Frontal width 1.9–2.0 ×interfrontal height. Interfrontal bristles in 3–4 larger subequal pairs surmounting smaller 4 th /5 th pair. Vibrissal angle with 2–3 subvibrissal setulae; gena with strong upcurved seta and 5–7 setulae, lower half with brown microtomentum. Face evenly rounded ventromedially; palpus with two subapical setae and several small setulae. Antennal pedicel large, at least 0.7×size of postpedicel; postpedicel spherical. Eye height 2.2–2.4×genal height. Thorax dark brown. Three pairs of distinct dorsocentral bristles, anterior-most pair at level of suture and only slightly larger than acrostichals, middle pair 0.5 ×length of prescutellar pair, separated by 8–10 rows of acrostichal setulae. Outer postpronotal bristle large and inner bristle smaller. Anepisternum with vertical, posterodorsal row of 2–3 setae, otherwise bare; katepisternum with moderate anterior seta, very large posterior seta and several smaller ventral setae. Scutellum subtriangular, length 0.5–0.6 ×its width. Legs dark brown; tarsi brown. Mid tibia with four dorsal bristles (two anterodorsal and two posterodorsal, none paired) in proximal half and four dorsal bristles (one anterodorsal, two dorsal, and one posterodorsal, larger bristles paired) in distal half. Ventral surface of mid tibia with distal row of stout setae in males (mid femur with corresponding row of strong proximoventral setae). Wing (Fig. 5A) evenly infuscate. CS2 0.7–0.8 ×length of CS3. R 4+5 gently upcurved, meeting costa before wing tip; costa extending far beyond apex of R 4+5 (5–6×costal width). M 1 and M 4 pseudoveins extending beyond dm-m approximately half way to wing margin; crossvein r-m at 0.3 ×length of R 4+5, crossveins separated by 1.4–1.5 × length of dm-m; CuA+CuP sinuate but weakly defined. Alula small and parallel-sided, length 4.5×width. Halter pale brown.
MALE ABDOMEN (Figs 2B–C, 3, 5B). S5 long setose with broad posteromedial emargination flanked by lateral patches of stout, blunt setae. S6+7 simple and unmodified; S7 with small dextral extension. Epandrium large (subequal to eye); cercus small, subtriangular, and slightly flared posteriorly with two long setae; subepandrial sclerite well-developed, broad and bent dorsally, ventrally tapered to a narrow, dark stripe. Hypandrium Y-shaped, anteromedial apodeme very broad; lateral arm with knoblike ventral lobe. Surstylus short, trilobed: the anterior lobe rectangular with two very long, curled setae, mediolateral lobe triangular with several setulae, posterior lobe semicircular with three thick, tooth-like ventral setae and several smaller inner setae. Postgonites broad, slightly curved forwards and constricted in apical third, apex rounded with several minute setulae. Phallapodeme elongate and sinuate; basiphallus large (0.5×postgonite length), wedge-shaped; epiphallus downcurved and tapered. Distiphallus composed of several sclerites and divided into basal and apical sections: basal section composed of a saddle-shaped upper sclerite which curves around to a triangular lower sclerite; apical section composed of a dark, curved, rectangular upper anterior sclerite and two elongate, curved, lower lateral sclerites which together support sheet-like membranous apex.
FEMALE ABDOMEN (Fig. 4). Postabdomen elongate, segments 6–8 fitting into segment 5 at rest; when everted, postabdomen ~50% of the total abdominal length. T6–7 and S6–7 elongate but reduced, appearing as thin, medially-desclerotized, rectangular or bell-shaped plates and posteriorly bearing 6–8 setae. T8 divided into two elongate, posteriorly setulose, lateral sclerites. Epiproct rectangular, medially desclerotized with pair of dorsal setae. Cercus short, ovoid, with several long sinuate setae. S8 ovoid, anteromedially reduced and posteriorly densely setulose. Hypoproct broad but short, with 8–10 posterior setulae. Spermathecae stout, spherical, strongly grooved with apical invagination.
Remarks
This species is much smaller and less colourful than other species of Pleuroseta, from which it differs widely in the structure of the male genitalia, and in having elongate, telescopic female terminalia similar to those of most macropterous Howickia. It is here provisionally included in Pleuroseta on the basis of the diagnostic posterior anepisternal setae, the third dorsocentral bristle, and the enlarged mid basitarsal seta. Pleuroseta occidentalis sp. nov. is the only species of Pleuroseta known from Western Australia and the only species not known from Queensland.
description: Published as part of Kuwahara, Gregory K. & Marshall, Stephen A., 2023, A revision of the Australian genus Pleuroseta Richards (Diptera, Sphaeroceridae), pp. 69-97 in European Journal of Taxonomy 910 on pages 74-80, DOI: 10.5852/ejt.2023.910.2361, http://zenodo.org/record/10306494