Pseudomyrmex mixtecus 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 mixtecus Ward , sp. nov.

(Figs. 15, 26, 55, 61, 69)

Holotype worker. - MEXICO, Guerrero: 25.4 mi. S. Chilpancingo , 10. viii. 1966, D. H. Janzen #M008810966 ( LACM). HW 0.97, HL 1.07, EL 0.48, PL 0.55, PH 0.35 .

Paratypes. - Same data as holotype, and three other accession numbers ( M 007810966 , M 009810966 , M 010810966 ) with same locality, date, and collector: series of 43 workers, 34 queens and 17 males ( AMNH, BMNH, CASC, EBCC, GBFM, INBC, LACM, MCZC, MZSP, PSWC, UCDC, USNM). Additional non-type material is listed below .

Worker measurements (n - 13). - HLO. 94 - 1.19, HW 0.89 - 1.03, MFC 0.054 - 0.073, Cl 0.86 - 0.95, REL 0.42 - 0.47, REL 2 0.46 - 0.52 OOI 1.22 - 2.28, VI 0.61 - 0.73, FCI 0.056 - 0.073, SI 0.43 - 0.45, SI 2 0.86 - 0.97, NI 0.60 - 0.65, PLI 0.60 - 0.68, PWI 0.60 - 0.68, PPWI 1.40 - 1.73.

Worker diagnosis. - Similar to P. ferrugineus (q. v.) except as follows. Size smaller (HW <1.04, LHT <0.90), head broad (Cl> 0.85); frontal carinae separated by about basal scape width or less (FCI 2 0.45 - 0.54). Basal and declivitous faces of propodeum forming a less obtuse angle in profile than typical for P. ferrugineus (compare Figs. 26 and 27). Head densely punctulate, opaque. Standing pilosity rather common, usually some setae exceeding 0.12 mm and 0.20 mm in length on mesosoma dorsum and petiole, respectively. Pubescence dense but appressed. Very dark brown to black, appendages lighter.

Comments. - P. mixtecus is distinguished from all other species, except P. veneficus and P. flavicomis , by its laterally rounded median clypeal lobe, broad head, and black (or very dark brown) body. It differs from P. veneficus by the fully opaque head, absence of conspicuous suberect pubescence on the petiole, and larger size. P. mixtecus is evidently closely related to P. flavicomis but averages smaller in size (compare worker HW and LHT values), a difference which is absolute in queens (queenHW 0.96 - 1.01 (n = 8), whereas queen HW> 1.11 in P. flavicomis ). In addition the petiole is relatively longer and higher, for a given head width, in both workers and queens of P. mixtecus (Figs. 44-47).

Distribution and biology. - P. mixtecus is known only from the Mexican states of Guerrero and Oaxaca (Fig. 69). Colonies have been collected from Acacia hindsii and A. collinsii , but little more has been recorded about their biology. Janzen’s field notes indicate that this species is monogynous.

Material examined. Type material listed above, plus the following ( CUIC, LACM, MCZC, MZSP, PSWC, SEMC, USNM, WPMC ). -

MEXICO Gro.: 10mi NE Acapulco (D.H.Janzen) ; 29.6mi N Acapulco , 1400ft. (D.H.Janzen) ; 30mi N Acapulco, Hwy.95 (Cornell Univ. Mex. Field Party) ; 57.8mi S Chilpancingo, Hwy.95 (D.H.Janzen) ; 74km N Acapulco (W.MacKay) ; Acapulco (Baker ; F.Knab ; N.L.H.Krauss ; L.J.Lipovsky) ; Puerto Marques (N.L.H.Krauss) ; San Geronimo de Juarez (W.von Hagen) ; Oax.: 11.4-17.0mi W Tehuantepec (D.H.Janzen) ; 13.8mi W Tehuantepec , 1500ft. (D.H.Janzen) ; 19km N San Pedro Pochutla , 200m (W.MacKay) ; 6.0mi E Niltepec, Hwy. 190, 100m (D.H.Janzen) .