Pseudomyrmex janzeni

Colonies occupy Acacia hindsii and are polygynous; additional details of the life history can be found in Janzen's (1973) paper on polygynous acacia-ants.

Identification
Ward (1993) - Within the P. ferrugineus group P. janzeni can be characterized by its relatively small size (worker and queen HW < 1 .04), broad head (worker CI > 0.86), laterally rounded median clypeal lobe, and uniform orange-brown color. P. janzeni is evidently closely related to Pseudomyrmex ferrugineus (as surmised by Janzen 1973); all of the metric measurements and indices of these two species overlap, although there is a tendency for P. janzeni workers to have shorter, higher petioles. Workers and queens of P. janzeni are perhaps best distinguished from those of P. ferrugineus by the combination of lighter orange-brown color, suberect gular pubescence (best seen in a backlit lateral view of the head), and the flatter profile of the worker mesosoma (see description above). While some individuals of the highly variable P. ferrugineus approach these conditions there is no indication of a convergence towards this morphology in western Mexico (Guerrero) where populations of P. ferrugineus come closest to those of P. janzeni.

Distribution
Western Mexico

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico.

Nomenclature

 *  janzeni. Pseudomyrmex janzeni Ward, 1993: 143, figs. 19, 29, 64, 70 (w.q.m.) MEXICO.

Worker
Worker measurements (n = 12). —HL 1.00-1.18, HW 0.93-1.03, MFC 0.063-0.096, CI 0.88-0.94, REL 0.4S-0.47, REL2 0.49-0.S2, OOI 1.45-2.29, VI 0.58-0.68, FCI 0.068-0.098, SI 0.42-0.4S, SI2 0.84-0.91, NI 0.62-0.69, PLI 0.59-0.71, PWI 0.63-0.73, PPWI 1.37-1.73.

Very similar to P. ferrugineus (q.v.) except as follows. Size smaller, on average. In lateral view mesonotum less steeply inclined; basal and declivitous faces of Propodeum forming a less obtuse angle. Petiole shorter and higher, on average. Weak rugulo-punctate sculpture on Propodeum even less evident than in P. ferrugineus. Pubescence denser, becoming decumbent to suberect on parts of body, most notably the gula. Head and mesosoma rather light orange-brown, gaster the same or a slightly darker brown.

Type Material
Holotype worker. MEXICO, Nayarit: 60 mi. SE Acaponeta, Hwy. I5, l5.ix.1963, D. H. Janzen. HW 1.00, HL 1.08, EL O.51, PL O.55, PH 0.36.

Paratypes. Same data as holotype: series of 1 66 workers, 62 queens and 45 males (,, , , , , LACM, , , , , ).