(Figs. 40, 41, 72, 79; Plate 1, C)
HOLOTYPE WORKER. TL 6.10, HL 1.63, HW 1.78, FC 1.28, CS 1.70, SL 0.90, SI 1 51, SI 2 53, PML 1.0, PW 1.38, PMD 1.48, PMI 2 107 ML 1.48, PTLL 0.43, PTLH 0.73, PTDW 0.48, PPLL 0.41, PPLH 0.74, PPI 56, PPDW 0.53, PT / PP 90.
Mandible with four teeth. In full face view clypeus anteriorly deeply excavated, distinctly exceeding anterolateral frontal corners as a bilobed carinulate projection. Head somewhat wider than long (CI 109), preoccipital margin moderately concave. Frontal carinae distinctly narrower than head width (FI 139), evenly narrowing towards clypeus. With head in profile antennal scrobe reaching beyond middle of lateral side of head, merging into lateral sides posteriorly, glossy except transverse carinulae at rear. Genae and ventrolateral sides of head evenly carinate, preoccipital lobes reticulate. Eyes exceptionally large (EL 0.43, REL 0.26, with 18 ommatidia in the longest row), situated at about middle of lateral sides of head, the dorsal ocular margin confluent with the ventral scrobal margin. Dorsal surface of head anteriorly costulate with oblique anastomoses, posterior section reticulate, with additional faint microsculpture.
Promesonotal shield distinctly wider than long (PMI 138), lateral projections translucently fused, posterior projections absent, mesonotal hind margin with transverse ridge, thus entire propodeal declivity visible from above. Propodeal spines short (PSL 0.45) and in profile broadbased, in dorsal view acute and arcuate.
Petiole in lateral view elongately trapezoid, markedly higher than long (PTI 59), with anterior face more or less straight, roundly meeting oblique reticulate dorsum, the latter merging into rugose posterior face, ventrally strongly sinuate. Postpetiole dorsally nodiform with large anterio-basal tooth.
Gaster shiny, entirely microreticulate, striate at very base. Dorsal surfaces covered with scattered pilosity of shorter decumbent and longer more or less erect soft hairs.
WORKERS (n = 11). TL 6.10 - 7.75, HL 1.58 - 1.78, HW 1.78 - 2.10, FC 1.28 - 1.60, FI 131 - 144, CI 109 - 121, CS 1.70 - 1.94, SL 0.90 - 1.08, SI 1 48 - 53, SI 2 52 - 56, PML 1.0 - 1.25, PW 1.38 - 1.68, PMI 127 - 145, PMD 1.48 - 1.90, PMI 2 107 - 113, ML 1.48 - 1.83, PSL 0.45 - 0.60, PTLL 0.43 - 0.49, PTLH 0.73 - 0.88, PTI 53 - 60, PTDW 0.48 - 0.65, PPLL 0.40 - 0.48, PPLH 0.74 - 0.88, PPI 50 - 56, PPDW 0.53 - 0.66, PT / PP 90 - 104, EL 0.37 - 0.44, REL, with 17 - 21 ommatidia in the longest row.
ETYMOLOGY
Named for its restricted westerly distribution.
ADDITIONAL MATERIAL EXAMINED
Western Australia : Lyndon Stn [several localities possible] ( Snell ) ; Ashburton River , 22. vi. 1967 ( G. Campbell ) ; Jigalong ( J. Hickmer ) ; Ethel Creek , iv. 1993 ( P. A. Varris ) ; Mt. Whaleback , Newman , vii. 1984 ( K. J. Walker ) ; Manilya Stn. , vi. 1955 ( A. Douglas ) ; 80 km SBarradale , 22. vi. 1975 ( P. J. M. Greenslade ) ; 30 km SMinilya , 15. viii. 1984 ( B. B. Lowery ) ; S. bank of Gascoyne River , 10 km E ofH'way , 10. viii. 1983 ( B. B. Lowery ) ; 60 km N ofCarnarvon H'way , 12. viii. 1984 ( B. B. Lowery ) ; Carnarvon , Ellanella Rd. , 14. vii. 1969 ( L. E. Koch ). (63 workers in ANIC , JDMP , MCZC , NHMW , SAMA , USNM , WAMP ) .
DISCUSSION
M. occidentalis is found in two distinct color varieties. Workers in the type series and several additional samples are light-brown with the gaster and appendages ferrugineous. Other samples have the gaster and appendages brown with the remainder of the body piceous. Intermediate forms are so far unknown. Gynes in the the type sample are concolorous, males strictly bicolored. The species is not to be mixed up with any other by the large eyes and the unique promesonotal shield. Known from south-western and western coastal Australia.
