(Figs. 46, 47, 77, 82)
HOLOTYPE WORKER. TL 5.25, HL 1.20, HW 1.38, FC 1.10, CS 1.29, SL 0.78, SI 1 56, SI 2 60, PML 1.15, PW 1.33, PMD 1.50, PMI 2 113, ML 1.33, PTLL 0.38, PTLH 0.55, PTDW 0.40, PPLL 0.31, PPLH 0.55, PPI 57, PPDW 0.48, PT / PP 84.
Mandible with four teeth. In full face view the clypeal projection very similar to that of preceding species, with the anterior concavity somewhat broader and with anterolateral corners more blunt. Head moderately wider than long (CI 115), preoccipital margin almost straight. Frontal carinae markedly narrower than head width (FI 125), posteriorly almost parallel-sided, evenly curved towards clypeus. With head in profile antennal scrobe distinctly surpassing middle of lateral side of head, distinctly transversely carinulae at the rear, anteriorly with additional oblique carinulae, rather well defined posteriorly against remainder of head. Genae and ventrolateral sides of head rugoreticulate, preoccipital lobes coarsely reticulate. Eyes moderately large (EL 0.31, REL 0.26, with 15 ommatidia in the longest row), situated at about middle of lateral sides of head, the dorsal ocular margin confluent with the ventral scrobal margin. Frons anteriorly rugose, remainder of head coarsely rugoreticulate, interspaces glossy.
Promesonotal shield little wider than long (PMI 115), overhanging lateral sides of mesosoma and propodeal declivity, near lateral margin with translucent fenestra at level of promesonotal boarder. Mesonotum indented and projections well developed, translucently lamellate between projections. Propodeal spines in profile short (PSL 0.43), situated at about middle of lateral sides of the propodeal declivity, broad-based and acute, in dorsal view distinctly curved towards petiole.
Petiole higher than long (PTI 68), in lateral view an equilateral triangle with anterior and slightly convex posterior faces meeting in a crest, posterior face rugose. Postpetiole nodular with well developed anterio-basal tooth.
First gastral tergite entirely microreticulate. Dorsal surfaces covered with shorter decumbent and longer erect more or less setose hairs.
Distinctly bicolored as in preceding species.
WORKERS (n = 6). TL 4.80 - 5.25, HL 1.06 - 1.23, HW 1.24 - 1.40, FC 1.04 - 1.16, FI 117 - 125, CI 113 - 118, CS 1.15 - 1.31, SL 0.73 - 0.80, SI 1 56 - 59, SI 2 60 - 64, PML 1.03 - 1.15, PW 1.23 - 1.39, PMI 115 - 129, PMD 1.39 - 1.58, PMI 2 113 - 115, ML 1.13 - 1.33, PSL 0.39 - 0.45, PTLL 0.33 - 0.40, PTLH 0.51 - 0.58, PTI 63 - 70, PTDW 0.40 - 0.49, PPLL 0.30 - 0.38, PPLH 0.55 - 0.65, PPI 53 - 63, PPDW 0.47 - 0.50, PT / PP 84 - 99, EL 0.26 - 0.31, REL 0.24 - 0.26, with 14 - 17 ommatidia in the longest row.
ETYMOLOGY
The name refers to the incurved propodeal spines.
ADDITIONAL MATERIAL EXAMINED
South Australia : Cowarie , 1.2 km SWKalladeina Bore , 27. iv. 1995 ( T. Robinson ) ; 19.5 km WNWAnta Hill [=? Antakatanya Hill ], 16. - 19. ix. 1998 (coll. unknown) ; 22.5 km WSWHaines Hill (coll. unknown). 25.8 km NMiandana WH , 9. - 14. x. 1998 (coll. unknown) (7 workers in NHMW , SAMA ) .
DISCUSSION
M. arcuatus differs from other species by the distinctly incurved propodeal spines in addition to the triangular petiole and the outline of the promesonotal shield. Only known from the type locality and few samples in northeastern South Australia, with a wide gap in between.
