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Tetramorium placidumHNS sp. n.

(Fig. 46)

Holotype worker. TL 3.4, HL 0.76, HW 0.69, CI 91, SL 0.56, SI 81, PW 0.54, AL 0.92.

Mandibles coarsely longitudinally striate; anterior clypeal margin without a median impression. Frontal carinae feebly sinuate, strongly developed through most of their length but becoming weaker close to the occiput, scarcely more strongly developed than the remaining cephalic rugular sculpture. Antennal scrobes weak. Eyes of moderate size, maximum diameter 0.15, about 0.22 x HW, situated at the midlength of the sides of the head. Propodeal spines short and stout, basally broad but tapering to an acute and slightly upcurved apex. Metapleural lobes long and very narrowly triangular, about 0.75 x the length of the propodeal spines. Outline shape of alitrunk and pedicel as in Fig. 46. Dorsum of head finely reticulaterugulose from level of anterior margin of eye to occiput, the reticular cross-meshes only slightly weaker than the longitudinal components. Dorsal alitrunk reticulate-rugose. Ground sculpture of both head and dorsal alitrunk a feeble punctulation, effaced in places, especially between the alitrunkal reticulations. Dorsum of petiole irregularly rugulose, dorsum of postpetiole unsculptured, smooth and polished. First gastral tergite unsculptured except for pits from which hairs arise. Standing fine pilosity abundant on all dorsal surfaces but the leading edges of the antennal scapes and the dorsal (outer) surfaces of the hind tibiae only with short, fine hairs which are subdecumbent to decumbent. Colour reddish brown.

Paratype workers. As holotype, with range of dimensions TL 3.3 - 3.4, HL 0.76 - 0.78. HW 0.69 - 0.72, CI 91 - 92, SL 0.56 - 0.58, SI 80 - 84, PW 0.52 - 0.54, AL 0.90 - 0.92 (2 measured).

Holotype worker, Mexico: Jalisco, Puerto Los Mazos, 10 miles SW. Autlan 4400 ft, 25. ix. 1973, leaf litter forest floor (A. Newton) (MCZ, Cambridge).

Paratypes. 2 workers with same data as holotype (BMNH; LACM, Los Angeles).

Apart from the type-series a short series in alcohol is present in CAS, San Francisco (determined as spinosumHNS). These fit the above description but are lighter in colour (orange-yellow) and somewhat smaller than the types, HL 0.70 - 0.72, HW 0.66 - 0.68, CI 94, SL 0.50 - 0.52, SI 76, PW 0.50 - 0.52, AL 0.86 - 0.88 (3 measured). They come from Mexico: Nayarit, San Blas, 17. ix. 1953 (B. Malkin). This species is distinguished by its small size and unsculptured postpetiole.