Pheidole janzeni

Pheidole janzeni occurs in dry forest habitats.

Identification
The morphometric profile of Pheidole janzeni is unique. The extemely small minor workers have the habitus of Pheidole laselva and Pheidole nigricula, differing from those in the more extensive foveolate sculpture on the katepisternum and propodeum, and the shorter propodeal spines. The major worker differs from those species in the presence of shallow, smooth antennal scrobes surrounded by reticulate rugose sculpture.

Distribution based on Regional Taxon Lists
Neotropical Region: Costa Rica, El Salvador, Guatemala, Honduras, Mexico.

Biology
Longino (2009) - In Costa Rica, minor and major workers were collected at baits near a stream edge. Similarly, minor and major workers were collected at baits in dry forest localities in Chiapas, Mexico. Habitats have been open dry areas with frequent disturbance, including a recently slashed and burned field, and an area of heavy livestock use. An isolated minor worker was collected in pine oak forest at 1100m in Guatemala. It is likely that this species is common and widespread in seasonally dry areas of Mesoamerica but has been largely overlooked due to its small size.

The type series of Pheidole mackayi was from a bait and is a mixed series, with the minor workers being this newly described species and not conspecific with the holotype major worker of P. mackayi. The collections from Costa Rica and Mexico are remarkably similar and appear identical in every respect; they show no geographic variation.

Worker
Minor

Images from AntWeb
Major

Nomenclature

 *  janzeni. Pheidole janzeni Longino, 2009: 40, fig. 9 (s.w.) COSTA RICA.

Worker
Minor Measurements (paratype): HL 0.43, HW 0.39, HLA 0.11, SL 0.33, EL 0.10, ML 0.48, PSL 0.00, PMG 0.00, SPL 0.02, PTW 0.07, PPW 0.10, CI 91, SI 84, PSLI 0, PMGI 0, SPLI 5, PPI 154.

Measurements (n=6): HL 0.40-0.44, HW 0.36-0.40, SL 0.32-0.36, CI 90-91, SI 84-95.

Face smooth and shining; margin of vertex flattened with median impression; occipital carina narrow, not visible in full face view; scape with abundant suberect setae about as long as maximum width of scape; promesonotal groove absent; propodeal spines reduced to short obtuse angles; lateral face of pronotum and entire promesonotal dorsum smooth and shining; anepisternum foveolate; katepisternum with medial shiny area surrounded by foveolae; dorsal face of propodeum foveolate, posterior face smooth and shining, lateral face foveolate dorsally, smooth and shining ventrally; mesosomal dorsum with 8-12 medium-length clear (not black) erect setae; dorsal (outer) margin of hind tibia with short decumbent pilosity, no long erect hairs; first gastral tergum smooth and shining; gastral dorsum with moderately abundant, somewhat stiff erect setae; color dark brown to black.

Major Measurements (holotype): HL 0.74, HW 0.62, HLA 0.15, SL 0.32, EL 0.10, ML 0.62, PSL 0.01, PMG 0.00, SPL 0.03, PTW 0.11, PPW 0.18, IHT 0.12, OHT 0.24, CI 83, SI 52, PSLI 1, PMGI 0, SPLI 4, PPI 156, HTI 50.

Measurements (n=4): HL 0.73-0.81, HW 0.60-0.66, SL 0.32-0.36, CI 82-83, SI 51-57.

Mandibles smooth and shiny with 3–4 coarse, widely-separated longitudinal rugae on outer base, moderately abundant subdecumbent setae on dorsal surface; clypeus smooth and flat with shallow anterior notch; face with well-defined shallow antennal scrobes, medial area somewhat swollen, sloping to relatively depressed vertex lobes, scrobes smooth and shining, most of rest of face with reticulate rugose sculpture, extending to posterior margin of vertex, about 4 stronger longitudinal rugae on frontal space posterior to clypeus; in face view anterolateral margins of head slightly flaring at mandibular condyles; head with abundant short suberect setae projecting from sides of head in face view; scape smooth and shining, terete, with abundant erect setae longer than maximum width of scape; hypostomal margin gently curved; median tooth an inconspicuous short nub; inner hypostomal teeth small but distinct, slightly closer to midline than to outer hypostomal teeth; promesonotal groove absent, dorsal profile of promesonotum evenly arched; propodeal spines present, short; promesonotum smooth and shining with patch of foveolae and rugae on humeral angles; remaining mesosomal sculpture as in minor worker; dorsum of postpetiole smooth and shining; dorsal (outer) margin of hind tibia with short decumbent pilosity, no long erect hairs; pilosity abundant on mesosomal dorsum; first gastral tergite smooth and shining, with abundant erect setae; color dark brown.

Type Material
Holotype major worker. Costa Rica, Guanacaste: Santa Rosa National Park, Sector Murcielago campground, 10.90092°N 85.72943°W, ±100m, 50m, 27 Feb 2008 (J. Longino#6144.04), unique specimen identifier CASENT0608973.

Paratypes: major and minor workers. Same data as holotype, , EAPZ, ECOSCE, , , , , , , , , , ICN,.

Etymology
This species is named for an important mentor of mine, D. H. Janzen. It may seem odd to name such a diminutive species for a giant in tropical ecology, but (1) it is a distinctive species, unlikely to be synonymized, (2) it is widespread in synanthropic habitats, and thus likely to be frequently encountered for generations to come, and (3) it is found in tropical dry forest habitats, the conservation of which Janzen has championed.

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
 * Longino J. T. 2009. Additions to the taxonomy of New World Pheidole (Hymenoptera: Formicidae). Zootaxa 2181: 1-90.
 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133