Pseudomyrmex janzeni Ward, 1993

Ward, Philip S., 1993, Systematic studies on Pseudomyrmex acacia-ants (Hymenoptera: Formicidae: Pseudomyrmecinae), Journal of Hymenoptera Research 2, pp. 117-168 : 143

Pseudomyrmex janzeni Ward , sp. nov.

(Figs. 19, 29, 64, 70)

Holotype worker. - MEXICO, Nayarit: 60 mi. SE Acaponeta, Hwy. 15, 15.ix. 1963 , D. H. Janzen ( LACM). HW 1.00, HL 1.08, EL 0.51, PL 0.55, PH 0.36.

Paratypes. - Same data as holotype: series of 166 workers, 62 queens and 45 males ( AMNH, BMNH, CASC, EBCC, GBFM, INBC, LACM, MCZC, MZSP, PSWC, UCDC, USNM). Additional non-type material is listed below .

Worker measurements (n = 12). - HL 1.00-1.18, HW 0.93-1.03, MFC 0.063-0.096, Cl 0.88-0.94, REL 0.45-0.47, REL2 0.49-0.52, OOI 1.45-2.29, VI 0.58-0.68, FCI 0.068-0.098, SI 0.42-0.45, 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.

Worker diagnosis. - 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 (compare Figs. 27 and 29). Petiole shorter and higher, on average (Fig. 48). 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 (Fig. 19). Head and mesosoma rather light orange-brown, gaster the same or a slightly darker brown.

Comments. - Within the P. ferrugineus group P. janzeni can be characterized by its relatively small size (worker and queen HW <1.04), broad head (worker Cl> 0.86), laterally rounded median clypeal lobe, and uniform orange-brown color. P. janzeni is evidently closely related to P. 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 (Fig. 48). 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 and Fig. 29). 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 and biology. - First recognized by Janzen (1967a, 1969, 1973) as a distinct but undescribed species, P. janzeni is confined to a limited area in western Mexico (Fig. 70) where it is sympatric with the much darker colored and commoner P. veneficus . 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.

Material examined. Type material listed above, plus the following ( LACM, MCZC, PSWC, UCRC, USNM ). -

MEXICO Jal.: Puerto Vallarta (J.A.Comstock) ; Nay.: 14.5mi E San Blas (D.H.Janzen) ; 2mi E San Blas (R.van den Bosch) ; 31mi N Tepic (D.H.Janzen) ; 36mi N Tepic (D.H.Janzen) ; 4mi E San Blas (M.Irwin ; M.Irwin & E.I.Schlinger ; E.I.Schlinger) ; 5mi E San Blas (F.Parker & D.Miller) ; Compostela (c.u.) ; Rio Palillo, 14mi E San Bias (D.H.Janzen) ; Tepic (H.A.Scullen) ; Sin.: 20mi E Villa Union (E.I.Schlinger) .