Pheidole mackayi

This species occurs in disturbed habitats in seasonally dry climates, from 700-1400m elevation. The few collections, minor and major workers, have been from baits. The type colony was collected at a bait in a cut and burned-over forest area. (Wilson 2003, Longino 2009)

Identification
See the description in the nomenclature section.

Distribution
Chiapas.

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico.

Worker
Minor

Nomenclature

 *  mackayi. Pheidole mackayi Wilson, 2003: 448, figs. (s.w.) MEXICO. See also: Longino, 2009: 52.

Description
DIAGNOSIS Similar in various traits to Pheidole cerina, Pheidole hizemops, Pheidole micon, Pheidole tachirana and Pheidole tenebra, differing as follows.

Major: dark brown; in side view, promesonotal profile almost straight until it drops off posteriorly in a nearly vertical face to the metanotum; pronotum in dorsal-oblique view bilobous, and mesonotal convexity subangulate; eyes relatively large; propodeal spines curve backward; postpetiole from above diamond-shaped; posterior half of dorsal head surface smooth with widely scattered foveae. Minor: eye very large, almost circular, set well forward on head; propodeal spines reduced to denticles; occiput narrowed, its margin concave, lacking nuchal collar.

MEASUREMENTS (mm) Holotype major: HW 0.84, HL 0.86, SL 0.52, EL 0.12, PW 0.44. Paratype minor: HW 0.40, HL 0.44, SL 0.36, EL 0.08, PW 0.24. COLOR Major: body dark, almost blackish brown; appendages light brown.

Minor: body and antennae medium brown, legs yellow.



'''Figure. Upper: holotype, major. Lower: paratype, minor. Scale bars = 1 mm.'''

Longino (2009) discovered the type collection was a mixed series that included Pheidole janzeni and he redescribed Pheidole mackayi'' :

Worker
Minor Measurements (n=1): HL 0.60, HW 0.51, SL 0.65, HLA 0.21, EL 0.13, ML 0.73, PSL 0.05, PMG 0.02, SPL 0.02, PTW 0.11, PPW 0.16, CI 85, SI 126, PSLI 9, PMGI 4, SPLI 4, PPI 146.

Mandible roughened, dull at base, grading to smooth and shiny near masticatory margin; clypeus strongly convex, largely smooth and shining with 2–4 longitudinal rugulae; face largely smooth and shiny, with faint foveolate sculpture between frontal carina and compound eye, extending posterior to compound eye on side of head, small irregular patches of faint fovelate sculpture elsewhere; margin of vertex flattened posteriorly; occipital carina narrow, barely visible in full face view; scape foveolate, with abundant decumbent setae and sparse suberect setae that are subequal in length to maximum width of scape; promesonotal groove present; propodeal spines present; pronotum foveolate with dorsal shiny patch; katepisternum and propodeum foveolate; about 12 short, curved, somewhat stiffened setae on mesosomal dorsum; dorsal (outer) margin of hind tibia with short decumbent setae and sparse suberect setae that are subequal in length to maximum width of tibia; dorsal surface of postpetiole faintly foveolate; first gastral tergum with fine short striations near postpetiolar insertion, smooth and shining elsewhere; gastral dorsum with moderately abundant, somewhat stiff setae; color red brown.

Major Measurements (holotype): HL 0.86, HW 0.84, SL 0.52, EL 0.12, IHT 0.28, OHT 0.35, CI 98, SI 62, HTI 79.

Mandible shiny, with coarse piligerous puncta, coarse striae at base; clypeus smooth and flat with distinct anterior notch; frontal carinae somewhat elevated and laminar; face rugose foveolate on sides of head between frontal carina and compound eye, gradually fading behind eye to smooth and shiny vertex lobes (extent of shiny area variable), medial area an irregular mixture of smooth and shiny patches, longitudinal rugulae near frontal carinae, and patches of faint foveolate sculpture; posterior margin of vertex with sparse stiff erect setae, side of head in full face view with short appressed setae only, no projecting erect setae; scape foveolate, terete at base, with appressed pubescence and sparse erect setae subequal in length to maximum width of scape; hypostomal margin gently curved; median tooth small to absent; inner hypostomal teeth minute denticles (may be drawn out into thin, needle-like spines) closer to outer hypostomal teeth than to midline; promesonotal groove present; propodeal spines present; mesosoma largely foveolate with variable extent of shiny patch dorsally; dorsal (outer) margin of hind tibia with appressed pubescence and sparse erect setae subequal in length to maximum width of tibia; 12–14 stiff erect setae on mesosomal dorsum; postpetiole in dorsal view globular, wider than long, faintly foveolate; first gastral tergum with small area of fine short striations near postpetiolar insertion, smooth and shining elsewhere; gastral dorsum with abundant, somewhat stiff setae; color red brown.

Type Material
MEXICO: 24 km south of Cintalapa, Chiapas, col. William P. MacKay.

Etymology
Named after the collector and myrmecologist William P. MacKay.

References based on Global Ant Biodiversity Informatics

 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Wilson, E.O. 2003. Pheidole in the New World: A Dominant, Hyperdiverse Genus. Harvard University Press