Austroplebeia

Dollin, Anne E., Dollin, Leslie J. & Rasmussen, Claus, 2015, Australian and New Guinean Stingless Bees of the Genus Austroplebeia Moure (Hymenoptera: Apidae) — a revision, Zootaxa 4047 (1), pp. 1-73 : 24-25

Key to workers of the genus Austroplebeia

Remarks. In the workers, Austroplebeia species are most reliably identified using a series of mature foragers collected from a nest. The colour distinctions given in this key are relatively easy to see but can be misleading in individual specimens. Within a nest there are often workers with unusually dull or bright maculations ( Fig. 6 ). The most common colouration pattern seen in a series of nest-mates provides the most reliable species identification. Colour maculations and bristle colouration may also be under-developed in younger callow specimens.

The head width and HBW measurements provide more reliable identifications of individual specimens than the colour distinctions. Where the size ranges overlap, the colouration, pilosity and geographic origin of the specimen should be considered. The distributions given in some couplets are not mutually exclusive but are provided to help determine the correct choice.

Where these combined characters do not provide sufficiently clear identification, examination of worker sting rudiments ( Figs 15 , 16 ) may be necessary. If available, male genitalia ( Fig. 21 ), male mesepisternal pilosity ( Fig. 25 e–g) or queen metasomal pilosity ( Fig. 27 ) in specimens obtained from the same colony may assist in species identification.

1. Metepisternum with yellow-brown to yellow maculation ( Fig. 25 a). Paraocular area with cream to yellow maculation along orbital margins extending well above antennal sockets (Face Grades 9–14, Figs 1 , 22 a–b). Frons and mesepisternum with fine simple hair, lacking plumose hair or nearly so ( Figs 22 a–b, 25a). Distribution: New Guinea and northeastern QLD, Australia ( Fig. 28 a)............................................................................ A. cincta (Mocsáry)

- Metepisternal maculation absent (except in rare highly-coloured A. essingtoni specimens) ( Fig. 25 b). Paraocular area maculation absent or usually not extending above level of antennal sockets (Face Grades 0–8, Figs 1 , 22 c–f). Frons and mesepisternum with simple hair admixed with plumose hair ( Figs 22 c–f, 25 b). Distribution: WA, NT, QLD, NSW............... 2

2(1). Clypeus with an extensive cream maculation (Face Grades usually 5–6, ranging 4–8, Figs 1 , 3 , 22 c). Small bees, head width ≤ 1.67 mm ( Fig. 10 ), forewing including tegula ≤ 3.8 mm, HBW usually ≤ 0.30 mm ( Fig. 11 ). Distribution: WA, NT ( Fig. 28 b)................................................................................ A. essingtoni (Cockerell)

- Clypeus maculation restricted to lower margin or absent (Face Grades 0–4, rarely 5, Figs 1 , 3 , 22 d–f). Larger bees, head width ≥ 1.59 mm, usually> 1.65 mm ( Fig. 10 ), forewing including tegula ≥ 3.6 mm, HBW ≥ 0.29 mm ( Fig. 11 ). Distribution: WA, NT, QLD, NSW...................................................................................... 3

3(2). Thorax markings usually Grade 2–11 ( Figs 5 , 7 ). Pronotal collar and legs usually with cream or yellow maculations. Bristles on inner basitarsus III gold or pale gold. HBW mean = 0.35 mm (range 0.29–0.40 mm, n=361) ( Fig. 11 )................................................................................. A. australis (Friese) ... 4 (three colour morphs)

- Thorax markings usually Grades 0–2 ( Figs 5 , 7 ). Pronotal collar and legs usually lacking cream or yellow maculations. Bristles on inner basitarsus III brown or slightly brown. HBW mean = 0.41 mm (range 0.35–0.47 mm, n=173) ( Fig. 11 )......... 6

4(3). Thorax markings usually Grades 9–11 ( Figs 5 , 7 ). All tibiae usually with cream maculations. HBW mean = 0.34 mm (range 0.29–0.35 mm, n=139) ( Fig. 11 ). Distribution: northeastern WA, NT and western QLD ( Fig. 28 c)............................................................................................. A. australis –Central Colour Morph

- Thorax markings usually Grades 2–10 ( Figs 5 , 7 ). Leg maculations limited to a basal spot on tibia I. HBW mean = 0.36 mm (range 0.33–0.40 mm, n=220) ( Fig. 11 ). Distribution: QLD, NSW or far northern WA.............................. 5

5(4). Thorax markings usually Grades 2–5 ( Figs 5 , 7 ). Ventral scape lacking cream maculations. Distribution: QLD, NSW ( Fig. 28 c)...................................................................... A. australis – Eastern Colour Morph

- Thorax markings usually Grades 4, 9 or 10 ( Figs 5 , 7 ). Ventral scape often with cream maculations. Distribution: far northern WA ( Fig. 28 c).......................................................... A. australis – Western Colour Morph

6(3). Plumose hair on clypeus usually dense, integument barely visible among hairs ( Fig. 22 e). Bristles on scutellum usually coarse and opaque brown. HBW mean = 0.40 mm (range 0.35–0.44 mm, n=131) ( Fig. 11 ). Distribution: QLD ( Fig. 28 d)............................................................................................ A. cassiae (Cockerell)

- Plumose hair on clypeus usually more sparse, integument moderately visible among hairs ( Fig. 22 f). Bristles on scutellum finer with a slight brown tinge or pale. HBW mean = 0.42 mm (range 0.39–0.47 mm, n=42) ( Fig. 11 ). Distribution: NT and far northwestern QLD ( Fig. 28 d)............................................................. A. magna sp. nov.

Figures

FIGURE 1. Face colour marking grades used to classify Austroplebeia workers. In many specimens, these cuticle markings may be obscured by hair on the clypeus and paraocular area. Visualisation of these markings can be improved by tilting the bee's head back and viewing the face obliquely.

FIGURE 3. Variation in worker face colour grades observed within all Austroplebeia taxa except A. cincta. Data show 300 workers from 114 colonies, in addition to 50 workers from 10 flower samples of A. australis – Western Colour Morph. Colour grades are as illustrated in Fig. 1.

FIGURE 5. Thorax colour marking grades used to classify workers and males of Austroplebeia.

FIGURE 6. Number of different thorax colour marking grades found amongst workers within individual colonies of Austroplebeia. Data are based on 122 colonies and scores of 10 – 49 workers per colony.

FIGURE 7. Variation in worker thorax colour grades observed within all Austroplebeia taxa except A. cincta. Data show 2503 workers from 158 colonies, in addition to 59 workers from 15 flower samples of A. australis – Western Colour Morph. Colour grades are as illustrated in Fig. 5.

FIGURE 10. Ratio of head width and extent of thorax colour marking in workers of all Austroplebeia taxa except A. cincta. Data from 121 colonies are shown, in addition to five flower samples from A. australis – Western Colour Morph and one A. australis flower sample with mixed Western / Central characteristics. Data points are averages from 10 – 49 workers per colony, or 5 – 12 workers per flower sample. Data from eight individual type specimens are also shown. The T. symei and T. ornata types, in which the eyes are collapsed preventing accurate head width measurement, are not shown. The T. essingtoni holotype has a missing head, so data from the paratype are shown. 1. Colony F 31 from the northern tip of Cape York Peninsula, QLD, which has characteristics similar to A. australis – Eastern Colour Morph despite its geographic isolation. Names given in brackets in the legend are groups in our Halcroft et al. (2015) preliminary analysis.

FIGURE 11. Ratio of tibia III width and basitarsus III width in workers of all Austroplebeia taxa. Data from 173 colonies are shown, in addition to 26 flower samples: A. australis – Western Colour Morph (14 x), A. australis with mixed Western / Central characteristics (4 x) and NG A. cincta (8 x). Data points are averages from 2 – 4 workers per colony, or 1 – 12 workers per flower sample. Data from 12 individual type specimens are also shown. 1. Colony F 31 from the northern tip of Cape York Peninsula, QLD, which has characteristics similar to A. australis – Eastern Colour Morph despite its geographic isolation. Names given in brackets in the legend are groups in our Halcroft et al. (2015) preliminary analysis.

FIGURE 15. Worker sting rudiments metric data: ratio of maximum length of sting lancet (A) and shoulder width of gonostyli (B) in all Austroplebeia taxa. Data points are averages for 1 – 3 workers per nest or flower sample. 1. The geographically isolated colony, F 31, from the northern tip of Cape York Peninsula, QLD, which has colouring and HTW / HBW similar to A. australis – Eastern Colour Morph. 2. Colonies C 58 and D 55 from the ‘ intermediate’ group of Halcroft et al. (2015) which are consistent with A. australis – Eastern Colour Morph in this analysis. 3. CS- 8 workers, with Grade 4 Thorax Colour Markings, collected from flowers in the MacDonnell Ranges, NT. They are consistent with A. australis – Central Colour Morph in this analysis, despite their relatively dark colouration. 4. GS- 10 workers collected from flowers on the far western edge of the A. cassiae range. 5. NS- 7 workers collected from flowers on the far eastern edge of the A. magna sp. nov. range. Names given in brackets in the legend are groups in our Halcroft et al. (2015) preliminary analysis.

FIGURE 16. Austroplebeia worker sting rudiments: a, A. cincta NG; b. A. cincta QLD; c, A. essingtoni; d, A. australis – Eastern Colour Morph; e, A. australis – Central Colour Morph; f, A. australis – Western Colour Morph; g, A. cassiae; h, A. magna sp. nov. All drawn to same scale. Abbreviations: Gon—gonostylus; Sty—sting stylet (bulb); Lan—sting lancet (first valvula or first ramus).

FIGURE 21. Austroplebeia male genitalia. Figs a – c. Genitalia, dorsal view on left, ventral view on right: a, A. cincta; b, A. essingtoni; c, A. magna sp. nov. Figs d – e. Apical abdomen and protruding parts of genitalia, viewed laterally, as visible in many pinned male specimens: d, A. essingtoni, showing distinct curve in apical gonostylus; e. A. magna sp. nov., with gently curved apical gonostylus. Figs a – c drawn to same scale. Abbreviations: Pen—penis valve; Gon—gonostylus.

FIGURE 22. Austroplebeia worker faces: a, A. cincta NG; b, A. cincta QLD; c, A. essingtoni, showing a relatively heavily marked specimen within the species range; d, A. australis – Eastern Colour Morph; e, A. cassiae; f, A. magna sp. nov. Scale bars = 0.25 mm.

FIGURE 25. Austroplebeia lateral thoraces: Figs a – b. Worker mesosomal side: a, A. cincta QLD; b, A. cassiae. Figs c – d. Male mesosomal side: c, A. cincta QLD; d, A. cassiae. Figs e – g. Detail of mesepisternum pilosity on male mesosomal side (photographs by K. Walker): e, A. australis; f, A. cassiae; g, A. magna sp. nov. Figs e – g shown at same magnification; all scale bars = 0.25 mm. Abbreviation: Met—metepisternum.

FIGURE 27. Pilosity on apical part of Austroplebeia queen abdomen, viewed laterally: a, A. cassiae; b, A. magna sp. nov. Scale bars = 0.25 mm.

FIGURE 28. Observed distribution of all Austroplebeia species in Australia and the island of New Guinea: a, A. cincta; b, A. essingtoni; c, A. australis; d, A. magna sp. nov. and A. cassiae. In all maps, square symbols represent nest samples and circles represent samples collected from flowers or traps. The type locality for each named species, including those now synonymised, is indicated with arrows. Where the type locality was a general area such as ' Central Australia' or ' Cape York', these areas are indicated with shading.