Austroplebeia magna sp. nov.

(Figures 1–11, 13–25, 27–29, 32–33)

Diagnosis. In workers and males, frons and mesepisternum with plumose hair (Figs 22 f, 23f, 25g), head width ≥ 1.70 mm (Figs 10, 14). In workers, pronotal collar and legs without maculations, HBW 0.39–0.47 mm (Fig. 11). Most workers have the following characteristics: thorax markings Grades 0–2 (Figs 5, 7), plumose hair on clypeus sparser than in A. cassiae, integument moderately visible among hairs (Fig. 22 f), bristles on basitarsus III brown but bristles on scutellum slightly brown or pale. In males, gonostylus gently curved, thorax markings Grades 5–6 and 10–12, mesepisternum plumose hairs with long barbs at various angles and irregular in shape (Fig. 25 g), HBW 0.23–0.27 mm (Fig. 13), HTL 1.11–1.19 mm (Fig. 14). In queens, short dense hair covering T6, but absent on T4– T5 (Fig. 27 b). Distribution NT and far northwestern QLD (Fig. 28 d).

Description. As in A. cassiae, except for the following characters.

Worker. Holotype: Body 4.0 mm. Forewing (including tegula) 4.0 mm. All other measurements are listed in Table 4.

Structure. Head width 1.78 mm. Interocellar distance 1.8x ocellorbital distance. Clypeus length 0.5x width. Malar area 0.2x basal mandibular width. Scape length 0.8x alveolus–lateral ocellus distance.

Scutellum length 0.4x width. HBW 0.42 mm.

Colour. Face markings Grade 1. Thorax markings Grade 2, cream.

Pilosity. Density of plumose hair on clypeus moderately sparse. Vertex bristles slightly brown to brown. Long bristles on scutellum slightly brown. Bristles on inner surface of basitarsus III dark brown.

All other workers examined: Body 3.5–4.5 mm. Forewing (including tegula) 4.0– 4.5 mm. All other measurements are listed in Table 4.

Structure. Head width 1.72–1.90 mm. Interocellar distance 1.5–1.9x ocellorbital distance. Clypeus length 0.5– 0.6x width. Malar area 0.1–0.3x basal mandibular width. Scape length 0.7–0.9x alveolus–lateral ocellus distance.

Scutellum length 0.4x width. Wing venation shown in Fig. 18. First transverse cubital vein vestige (up to 75 Μm) present in 30% of wings examined and slight trace in 57% (n=53). Vein M of forewing terminates at or before position of anterior end of first recurrent vein in 90% of wings examined (n=54). Cell second Cu of forewing completely indicated by pigmented vein traces in 88% of wings examined (n=40). HBW very broad (Figs 11, 19 h), 0.39–0.47 mm.

Sting rudiments. Gonostyli shoulder width moderately broad, 0.12–0.15 mm. Apex of sting stylet usually with a narrowly rounded protrusion. Sting lancet length long, 0.33–0.37 mm (Figs 15, 16 h).

Colour. Face markings Grade 1, ranging 0–3a (Figs 1, 3). Thorax markings Grades 0–2 (Figs 5, 7), Grade 2 maculations: 56% brown, 44% cream.

Other areas with cream markings: pronotal lobe (sometimes dark brown to yellow-brown); sometimes labrum dull cream. Scape, pronotal collar, metasoma and legs without maculations.

Labrum brown, ranging red-brown to cream. Mandible: orange-brown medially, ranging red-brown to yellowbrown (Fig. 9); dark brown to orange-brown apically. Scape dark brown, sometimes red-brown. Tegula red-brown, ranging dark brown to brown. Basal and medial terga black to red-brown. Apical terga dark brown, ranging to brown (Fig. 9). Sterna usually dark brown.

Pilosity. Density of plumose hair on clypeus much sparser than that on paraocular area—revealing more of surface than in A. cassiae (Fig. 22 f). Vertex bristles slightly brown or brown.

Long bristles on scutellum slightly brown or pale—finer and paler than in A. cassiae.

In mature, fully coloured specimens: simple hairs of anterior and posterior corbicular fringes of tibia III slightly brown or pale, hairs on apical half of anterior fringe brown or slightly brown, basitarsus III inner surface with coarse brown bristles, deep opaque brown in some regions, becoming slightly brown on eastern end of distribution.

Geographic variation. The extent of thorax colour markings in A. magna sp. nov. workers was 0–4% (Fig. 10), similar to that of A. cassiae. However, some workers near Maningrida in Arnhem Land, NT, had Grade 0 face markings, darker than any observed A. cassiae workers.

In eastern populations, near the southern shore of the Gulf of Carpentaria, thorax colour markings were relatively bright (4%) and vertex, scutellum and basitarsus III bristles were relatively pale.

Male. As in A. cassiae, except for the following characters:

Body 4.0– 4.5 mm. Forewing (including tegula) 4.0– 4.5 mm. All other measurements are listed in Table 5.

Structure. Head width 1.70–1.82 mm. Interocellar distance 2.4–2.9x ocellorbital distance. Mandible preapical tooth more acutely pointed than A. cassiae but weaker than in A. cincta (Fig. 17 m). Flagellum relatively longer than in A. cincta, flagellum length 4.1–4.4x scape length.

HBW moderate, 0.23–0.27 mm. HTW moderate, 0.40–0.46 mm (Fig. 13). HTL moderate, 1.11–1.19 mm (Fig. 14).

Colour. Face markings usually Grades 17–18, sometimes 16 (Figs 2, 4). Thorax markings usually Grades 10– 12, sometimes 5 or 6 (Figs 5, 8).

Other areas with cream or yellow markings: ventral scape, labrum, all tibiae, all basitarsi (sometimes dull); usually basal mandible, pronotal lobe, a spot on tegula, apical terga and all femora; sometimes pronotal collar (spots on upper edge), metanotum, sterna and trochanters.

Mandible: cream, ranging to red-brown basally; orange-brown to cream medially (Fig. 9). Tegula dark brown to yellow brown, usually with a cream spot.

Pilosity. Mesepisternum plumose hair with barbs longer and sparser than A. cassiae, as in A. australis but varied in angle and overall shape very irregular (Fig. 25 g).

Queen. Body 5.0– 6.2 mm. Forewing (including tegula) 3.9–4.3 mm.

Structure. HBW 0.25–0.29 mm. Colour. Face markings up to Grade 2 (Fig. 24 f). Thorax markings up to Grade 4.

Pilosity. Clypeus with moderate density fine hair, mainly simple. Scutellum bristles slightly brown to brown and up to 450 Μm. T1–T5 with sparse fine short hairs, sparse longer (up to 275 Μm) coarse bristles on lateral and dorsal surfaces of T2–T5. T6 with short dense hair (Fig. 27 b) and an apical fringe of long (up to 375 Μm) simple hairs. Basitarsus III inner surface bristles brown.

Etymology. The Latin feminine adjective, magna, meaning 'large', refers to the broad basitarsus III and long sting lancet in workers of this species.

Material examined. Holotype. (AMS K.464902, worker), labelled as follows: “ HOLOTYPE / Austroplebeia magna / Dollin, Dollin & / Rasmussen 2015”, “Nest N2 / Worker”, “ AUSTRALIA, NT / 7k SW Katherine / 14.5o S, 132.2o E / 31 July 1987 / Anne & Les Dollin”

Paratypes. (ANIC 32-069967, worker), labelled as follows: “ PARATYPE / Austroplebeia magna / Dollin, Dollin & / Rasmussen 2015”, “Nest N2 / Worker”, “ AUSTRALIA, NT / 7k SW Katherine / 14.5o S, 132.2o E / 31 July 1987 / Anne & Les Dollin”. (ANIC 32-069968, male), labelled as follows: “ PARATYPE / Austroplebeia magna / Dollin, Dollin & / Rasmussen 2015”, “Nest N2 / Male”, “ AUSTRALIA, NT / 7k SW Katherine / 14.5o S, 132.2o E / 31 July 1987 / Anne & Les Dollin”. (AMS K.464903, male), labelled as follows: “ PARATYPE / Austroplebeia magna / Dollin, Dollin & / Rasmussen 2015”, “Nest N2 / Male”, “ AUSTRALIA, NT / 7k SW Katherine / 14.5o S, 132.2o E / 31 July 1987 / Anne & Les Dollin”.

Provenance of types: The holotype and paratypes were all collected from colony N2 of A. magna sp. nov. during an expedition to the NT by Anne and Les Dollin in July–September 1987. Anne and Les Dollin conducted ten major expeditions from 1980 to 2012 to investigate the distribution and characteristics of all species of Australian stingless bees.

Other worker and male specimens examined. Northern Territory: Nest samples, collected by AED & LJD except where otherwise stated: Cobourg Peninsula, 14–19 Aug 1987 (Nest N8, 20 workers, 15 males; Nest N12, 20 workers, 11 males; Nest N14, 10 workers); Buluhkaduru outstation, 50K SE Maningrida, 13–14 Aug 2014 (all by Aung Si: Nest D65, 11 workers, 11 males; Nest D66, 18 workers, 7 males; Nest D67, 28 workers); 7k SW Katherine, 31 Jul 1987 (Nest N1, 20 workers, 2 males; Nest N2, 20 workers, 15 males); Willeroo Station, 120k SW Katherine, Oct 2011 (Nest D57, 20 workers, A. Beil). — Samples collected from flowers or traps: Arnhem Bay, 17 May 1970, N Peterson, AMS, 3 workers; Adelaide R, 28 Sep 1985, AED & LJD, WS-21: 1 worker; 13k W Victoria River, 5 Jan 1989, TF Houston, WAM, 5 workers; Timber Creek, 27 Sep 1985, AED & LJD, WS-19: 4 workers; 68k E Timber Creek, 20 Apr 1980, G Anderson & D Symon, WAM, 2 workers; Roper Bar, 25 Aug 1987, AED & LJD, NS-1: 2 workers; 100k SE Roper Bar, 26 Aug 1987, AED & LJD, NS-3, 2 workers; 260k SE Roper Bar, 28 Aug 1987, AED & LJD, NS-4, 1 worker; Grose Lagoon, 11k SW byS Borroloola, 31 Oct 1975, JC Cardale, ANIC, 12 workers; Caranbirini Waterhole, 33k SW Borroloola, 3 Nov 1975, JC Cardale, ANIC, 6 workers; McArthur River, 14k S byW of Cape Crawford, 25 Oct 1975, JC Cardale, ANIC, 7 workers. Queensland: Sample collected from flowers: 10k NW Westmoreland Station, 20k E of NT/ QLD border, 29 Aug 1987, AED & LJD, NS-7: 15 workers.

Queen specimens examined. Nest samples collected by AED & LJD, 11 queens: Northern territory: Cobourg Peninsula, 14–19 Aug 1987 (Nest N8, 1 virgin; Nest N12, 6 virgin); Katherine, 31 Jul 1987 (Nest N1, 4 virgin).

Remarks. The NT populations here identified as A. magna sp. nov. were part of the 'symei' group defined in our preliminary studies (Halcroft et al. 2015). That group was characterised by its dark colouration (Thorax Grades predominantly 0–2, Fig. 5). It also included the eastern species, A. cassiae.

Although superficially similar to A. cassiae in size and colouration, A. magna workers could be distinguished by their broad basitarsus III, long sting lancet and fine clypeus hair. The structure of the mesepisternum plumose hairs differed in males of A. cassiae and A. magna (Figs 25 f–g). In addition, the dense layer of hair on T4–T5, seen in queens of A. cassiae, was absent in A. magna (Fig. 27). The broadest basitarsus III observed in the Austroplebeia was in a worker collected from an A. magna colony at Cobourg Peninsula, NT, in the far north of the species range.

Some A. magna workers from near Maningrida, NT, completely lacked pale markings on both the face and thorax. These were the darkest bees observed in the study. All other Austroplebeia workers that we have examined have had at least a dull maculation in the supraclypeal area.

The holotype and paratypes were all collected in 1987 from colony N2 near the middle of the geographic range of this species. The colouration, pilosity characteristics and structural data of the holotype and paratype specimens are all within the ranges described above for A. magna. The holotype (AMS K.464902) and the worker paratype (ANIC 32-069967) are both Face Grade 1, Thorax Grade 2, HBW 0.42 mm (Figs 1, 3, 5, 7, 10, 11, Table 4). One male paratype (AMS K.464903) is Face Grade 17, Thorax Grade 10, HBW 0.24 mm, HTL 1.15 mm; and the other male paratype (ANIC 32-069968) is Face Grade 17, Thorax Grade 5, HBW 0.23 mm, HTL 1.14 mm (Figs 2, 4, 5, 8, 13, 14).

*Variables: as given in Table 2.

The following male specimens were measured. A. cincta, N=6 unless otherwise stated, from nests D10 (3x), D14 (3x). A. essingtoni, N=5 unless otherwise stated, from nests N11, N15, W5, W9, W12. A. australis –Central Colour Morph, N=5, from nests C49, N3, Q33, W13, W17. A. australis –Eastern Colour Morph, N=5, from nests C72, C75, F31, NSW55, S2. A. cassiae, N=5, from nests D19, F6, F43, M19, N23. A. magna, N=5, from nests N1, N2, N8, N12 (2x). A. N=5; B. N=4