Myrmecia pilosula

Taylor, Robert W., 2015, Ants with Attitude: Australian Jack-jumpers of the Myrmecia pilosula species complex, with descriptions of four new species (Hymenoptera: Formicidae: Myrmeciinae), Zootaxa 3911 (4), pp. 493-520 : 497-498

Key to species of the M. pilosula complex (workers)

Notes:

(1) The use of characters involving pubescence is compromised if subject specimens are greasy.

(2) M. imaii is currently the only pilosula -complex species known from WA.

(3) Likewise the Western Race of M. pilosula is the only relevant taxon presently known from Western Victoria and SA, including Kangaroo Island.

(4) All known Tasmanian specimens not identified as the easily recognized M. haskinsorum are referable to the Western Race of M. pilosula .

(5) The eastern, hybrid-originated species M. impaternata is chromosomally very different from the WA M. imaii and the two could not possibly be considered conspecific. They are however morphologically similar, so the provenance of specimens can be important for their identification. The color of the brassy cephalic pubescence in M. impaternata can be hard to perceive in some lights. It is best seen in acute lateral diagonal view of the frons, across the near-side eye.

(6) The sculptural characters used in couplet 6 vary allometrically in both subject species, such that large specimens of eastern M. pilosula can be confused with M. croslandi by inexperienced identifiers. Small M. pilosula (Eastern Race) and large croslandi specimens are readily distinguished, so that the collection and consultation of specimens in size- ranged series is desirable.

1 Pilosity essentially lacking on all body surfaces except gastral apex, propleurae and undersides of head, postpetiole and gaster. Dorsal profile from mesonotum to first gastral tergite thus uninterrupted by standing hairs (a very few, very short minute bristles occasionally present) ( Fig 2 ). Anterior femora more or less uniformly dark brown, without distinct reddish-orange apical sections matching the adjacent tibiae and tarsi (the femoral apices at most only very vaguely infuscated) ( Fig 2 ). Middle and hind legs also generally dark brown, without reddish-orange segments, tarsi slightly less dark, lightest apically.( Fig 2 ). (Snowy Mountains, NSW Southern Tablelands, VIC Alps, TAS).......................................... M. haskinsorum .

- Relevant sections of dorsal body profile interrupted by numerous short standing bristles or longer hairs ( Figs 5 , 20 ). Anterior femora each with a distinct gradational reddish-orange apical section, colored like the adjacent tibia and contrasting with the dark brown femoral ground color ( Fig 5 ). Middle and/or hind legs often with some reddish-orange segments beyond the femora................................................................................................ 2.

2 Pubescence on clypeus and between frontal carinae and eyes distinctly brassy yellow (best observed in lateral oblique view), usually dense ( Figs 4, 5 , 16, 17 , 19, 20 )................................................................... 3.

- Pubescence on clypeus and between frontal carinae and eyes silvery white (described as “ashy” by Smith, 1858) often dense, sometimes diffuse. ( Figs 7, 8 , 14 ) (See notes (4) and (6) above)................................................ 5.

3 Head, when viewed obliquely from above and behind, with a strong overall greenish-gold caste provided by the minute elements of dense brassy pubescence which crowd the surfaces between fine longitudinal sculptural costulae ( Figs 4–6 ). (Coastal NSW, from just south of Sydney, south at least to Batemans Bay, currently unknown from elevations above ca 150m.).................................................................................................. M. banksi .

- Cephalic pubescence and resulting color cast in oblique posterior view of head much less strongly developed. Species from much higher elevations on or around the New England and Southern Tablelands of NSW, the ACT or southwestern WA ( Figs 19, 20 ) (See notes (2) and (4) above)..................................................................... 4.

4 Middle leg tibiae and tarsi reddish-orange, usually less bright than those of fore legs (the hind legs more or less uniformly dark brown, matching anterior and middle femora). Cephalic pubescence relatively prominent. (New England and Southern Tablelands of NSW and surrounding areas, including ACT) ( Figs 16–18 ).................................. M. impaternata .

- Middle and hind legs more or less entirely dark brown, matching anterior femora. Cephalic pubescence less well developed ( Figs 19–21 ). (extreme southwestern WA.)........................................................... M. imaii .

5 Hind legs consistently almost entirely dark brown, the tarsi slightly lighter. Middle leg femora similarly colored but the tibiae and tarsi usually reddish-orange, though sometimes brown like the femora....................................... 6.

- Hind and middle tibiae and tarsi bright reddish-orange, matching those of the anterior legs. In Tasmania, where this is the only species additional to M. haskinsorum (eliminated in couplet 1 above), some individuals in nests which otherwise conform to this diagnosis may have the middle and hind tibiae brown, as in the alternative prescription. ( Figs 13–15 ) (SA, including Kangaroo Island; VIC, generally west of longitude 145E and TAS)............................ M. pilosula (Western Race).

6 Mesonotum usually obscurely shagreened and “leathery” in appearance; often with effaced or vestigial longitudinal striae, less strong than those of the pronotum ( Fig 12 ). (Usually much less distinctly sculptured than in the opposed M. croslandi , except in large specimens). Petiolar dorsum less heavily sculptured than propodeal dorsum. The node at most bearing effaced coarse punctate rugosity, with the punctural elements clearly expressed, at least finely shagreened with a leathery appearance and almost smooth (especially medially) though not strongly reflective due to effaced traces of puncturation. (In intermediate individuals the rugosity appears to break down to coarse puncturation, which becomes peripheral and more spaced as the disk of the node becomes more nearly smooth). Pronotal and propodeal sculpture in general less strongly expressed than in M. croslandi . These features vary allometrically and are strongest in larger specimens. Petiole in dorsal view ( Fig 12 ) generally smaller and less-bulky than in the alternative M. croslandi but less clearly distinguished in larger specimens ( Figs 10–12 ) (eastern NSW, ACT and VIC, generally east of longitude 144E)............................... M. pilosula (Eastern Race).

- Mesonotum distinctly longitudinally striate rugose, the elements clearly incised ( Fig 9 ), generally a little less strongly developed than those of pronotal dorsum. Petiolar dorsum relatively heavily sculptured with medium, generally transverse rugosity; the elements almost as strong as those of the adjacent propodeal dorsum but relatively wavy, with clear radial and/or circular trends in some specimens and little trace of associated coarse puncturation. These features vary allometrically and are strongest in larger specimens. Petiole in dorsal view relatively large and bulky ( Figs 11, 12 ) (eastern NSW, ACT; notably New England and Southern Tablelands, with scattered records south at least to Warrandyte, VIC)........................ M. croslandi .

Figures

FIGURES 1 – 3. Myrmecia haskinsorum, Jamberoo, NSW. Standard views. HW 2.46 mm, WL 3.64 mm, PW 1.57 mm.

FIGURES 4 – 6. Myrmecia banksi, Holotype, South Nowra, NSW. Standard views. HW 2.66 mm, WL 3.86 mm, PW 1.72 mm.

FIGURES 19 – 21. Myrmecia imaii, Holotype, N of Denmark, WA. Standard views. HW 2.68 mm, WL 3.90 mm, PW 1.63 mm.

FIGURES 16 – 18. Myrmecia impaternata, National Botanic Gardens, Canberra, ACT. Standard views. HW 2.29 mm, WL 3.35 mm, PW 1.42 mm.

FIGURES 7 – 9. Myrmecia croslandi, Canberra, ACT. Standard views. HW 2.50 mm, WL 3.74 mm, PW 1.60 mm.

FIGURES 13 – 15. Myrmecia pilosula, Western Race, Mt Wellington, Tasmania. Standard views. HW 2.45 mm, WL 3.63 mm, PW 1.49 mm.

FIGURES 10 – 12. Myrmecia pilosula, Eastern Race, Mongarlowe, NSW. Standard views. HW 2.12 mm, WL 3.11 mm, PW 1.26 mm.