Pseudomyrmex championi

Pseudomyrmex championi occurs in the Sierra Madre Occidental, Sierra Madre del Sur, and the intervening Transmexican Volcanic Belt (Fig. 21). Collection labels with habitat and/or elevation information document the occurrence of this species in oak woodland, oak-pine forest, old field/pasture, mixed tropical/temperate mesic forest, mid-montane dry forest, and yucca desert, at elevations ranging from 1,200 m to 2,344 m (mean 1,828 m; n = 28). Four nests of P. championi encountered by one of us (P.S.Ward) were all from dead twigs of woody shrubs (one Asteraceae, one Verbenaceae, and two unidentified plants). (Ward & Branstetter, 2022)

Identification
Small to medium-sized species (HW 0.82–1.05) with moderately elongate head (CI 0.80–0.87) (Fig. 6) and relatively short eyes (see REL and REL2 values); frontal carinae separated by about basal scape width or less; metanotal groove present but weakly impressed; in profile, dorsal face of propodeum generally flat and more or less differentiated from declivitous face, rounding into the latter, and the two faces subequal in length; petiole moderately slender (PLI 0.49–0.57, PL/HL 0.52–0.56); in profile petiole with slight or no anterior peduncle, the anterodorsal face flat to convex, ascending gradually to summit in posterior half of node, then rounding into more steeply descending posterior face; profemur slender; hind leg relatively short (LHT/HL 0.69–0.75). Head opaque to subopaque, densely punctulate-coriarious, the punctulae on vertex usually separated by less than their diameters (but separated by more than their diameters in some populations, and the vertex correspondingly shinier). Standing pilosity sparse, absent from propodeum and mesonotum (MSC 4–8). Gaster, metacoxa, metafemur and metatibia dark brown, contrasting with light orangebrown mesosoma; head, first and second pairs of legs, petiole, and postpetiole varying from dark brown (usually) to much lighter and concolorous with mesosoma. (Ward & Branstetter, 2022)

The worker of this species is characterized by having a light-colored (orange-brown) mesosoma and contrasting dark gaster and hind leg. The head, other legs, petiole, and postpetiole also tend to be strongly infuscated, but in some samples (from Colima, Jalisco, and Chihuahua) they are lighter colored and even concolorous with the mesosoma. Workers of the closely related Pseudomyrmex apache are uniformly orange-brown in color; see further discussion under that species. Pseudomyrmex championi has been confused with dark brown workers of a more distantly related species, Pseudomyrmex cognatus, which occurs from southern Mexico to Nicaragua. The supposed descriptions of the larva (Wheeler and Bailey 1920, Wheeler and Wheeler 1956) and queen (Kempf 1961) of P. championi actually refer to P. cognatus. Workers of the two taxa can be distinguished as follows: P. championi is conspicuously bicolored, the dark gaster contrasting with the light orange-brown mesosoma, whereas P. cognatus is more uniformly dark brownish-black, with the mesosoma at most moderately lighter (and often dark on top); the metanotal groove is better developed (but still slight) in P. championi compared to P. cognatus; and the eye is generally shorter in P. championi than P. cognatus (REL 0.38–0.44 vs 0.43–0.48). The geographical distributions of P. championi and P. cognatus do not overlap (Figs. 21 and 22) but because they belong to different species complexes in the P. elongatulus group (Fig. 1), they cannot be treated as allopatric variants of the same species. Their similarities must reflect convergence or shared ancestral features. (Ward & Branstetter, 2022)

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico.

Nomenclature

 *  championi. Pseudomyrma championi Forel, 1899c: 96 (w.) MEXICO. Wheeler, G.C. & Wheeler, J. 1956: 382 (l.); Kempf, 1961a: 392 (q.). Combination in Pseudomyrmex: Wheeler, G.C. & Wheeler, J. 1956: 382. Senior synonym of leonhardi: Kempf, 1961a: 391.
 * leonhardi. Pseudomyrma leonhardi Stitz, 1937: 132, figs. (w.) MEXICO. Junior synonym of championi: Kempf, 1961a: 391.

Type Material

 * Pseudomyrma championi. Syntype worker, Amula, 6000 ft., Guerrero, Mexico (H. H. Smith) (BMNH) [examined by Ward & Branstetter, 2022].
 * Pseudomyrma leonhardi. Two syntype workers, Guerrero, Mexico (L. Schultze) (ZMHB) [examined by Ward & Branstetter, 2022].

References based on Global Ant Biodiversity Informatics

 * Castano-Meneses, G., M. Vasquez-Bolanos, J. L. Navarrete-Heredia, G. A. Quiroz-Rocha, and I. Alcala-Martinez. 2015. Avances de Formicidae de Mexico. Universidad Nacional Autonoma de Mexico.
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Field Museum Collection, Chicago, Illinois (C. Moreau)
 * Kempf W. W. 1961. Estudos sôbre Pseudomyrmex. III. (Hymenoptera: Formicidae). Studia Entomologica 4: 369-408.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Longino J. T. 2013. Ants of Nicargua. Consulted on 18 Jan 2013. https://sites.google.com/site/longinollama/reports/ants-of-nicaragua
 * Lopez, A. S., M. Vasquez-Bolanos, and G. A. Q. Rocha. 2015. Hormigas (Hymenoptera: Formicidae) del Cerro de la Culebra, Arandas, Jalisco, Mexico. Dugesiana 19: 151-155.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Wheeler, William Morton. 1916. Ants Collected in Trinidad by Professor Roland Thaxter, Mr. F. W. Urich, and Others. Bulletin of the Museum of Comparitive Zoology at Harvard University. 40(8):322-330