Tetramorium pacificum Mayr , 1870: 972, 976. Syntype workers, female, Tonga: Tongatabu (BMNH; NM, Vienna) [examined]. [For a statement of current synonymy oi pacificum see Bolton, 1977: 102.]
Worker. TL 3.7 - 4.6, HL 0.86 - 1.10, HW 0.72 - 1.02, CI 83 - 90, SL 0.62 - 0.82, SI 79 - 87, PW 0.54 - 0.68, AL 1.04 - 1.30 (45 measured).
Mandibles usually unsculptured except for hair-pits but in some populations with feeble traces of striation. Anterior clypeal margin with a median notch or impression; median portion of clypeus with three strong longitudinal carinae. Frontal carinae long and strongly developed, usually approaching the occipital margin. Maximum diameter of eye c. 0.18 - 0.21, about 0.22 - 0.25 x HW. Propodeal spines long and acute, usually narrow and often somewhat upcurved along their length. Metapleural lobes acute and upcurved, usually broad. Petiole in profile characteristically shaped (Fig. 44), with the posterior face higher than the anterior so that the convex dorsum slopes upwards posteriorly and the posterodorsal angle is higher than the anterodorsal. Anterior face and dorsum confluent through a curve. Sculpture variable in density and intensity. On the head varying from a blanketing rugoreticulum to a system which is predominantly longitudinal but with cross-meshes present from the level of the anterior margins of the eyes; always with a reticulum posteriorly, close to the occiput. Ground-sculpture between rugae superficial but quite conspicuous. Dorsal alitrunk reticulate-rugose; often pedicel segments similarly sculptured but in some the sculpture predominantly longitudinal. First gastral tergite usually with at least traces of basal costulae; although these are often vestigial they are only rarely completely absent. Erect or suberect long hairs numerous on all dorsal surfaces of head and body. Colour a uniform dark brown, blackish brown or black.
T. pacificum ranges throughout the Oriental and Indo-Australian regions and occurs in northern Australia. It is very widespread in most or all of the island-systems of the Pacific (Wilson & Taylor, 1967; Bolton, 1977) and has been recorded from California in the U. S. A. (M. R. Smith, 1943 ; Creighton, 1950). The shape of the petiole in pacificum is unique amongst tetramoriines occurring in the New World and should serve to identify instantly this species.
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