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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) [INBC, unique specimen identifier CASENT0608973].
Paratypes: major and minor workers. Same data as holotype [BMNH, CAS, EAPZ, ECOSCE, FMNH, INBC, JTLC, LACM, MCZ, MHNG, MIZA, MZSP, UCD, ICN, USNM].
Costa Rica, Guatemala, Mexico (Chiapas).
The morphometric profile of Pheidole janzeniHNS is unique. The extemely small minor workers have the habitus of P. laselvaHNS and P. 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.
Description of minor worker
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.
Description of major worker
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.
Pheidole janzeniHNS occurs in dry forest habitats. 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.
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.
The type series of P. mackayiHNS 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. mackayiHNS. The collections from Costa Rica and Mexico are remarkably similar and appear identical in every respect; they show no geographic variation.
Additional material examined
GUATEMALA: Zacapa, 8.5km NE Tuculutan, 15°03'31"N, 89°40'35"W, 1100m (M. Branstetter); MEXICO: Chiapas, Sierra Morena, 16°09'15"N, 93°35'23"W, 1150m (J. Longino); 24km SW Cintalapa, 16°32'N, 93°53'W, 710m (W. MacKay).
Found most commonly in these habitats: 42 times found in tropical moist forest, 4 times found in tropical dry forest, 14 times found in tropical rainforest, 1 times found in mature wet forest, 3 times found in 2º tropical rainforest, 3 times found in 2º lowland rainforest, 2 times found in slashed and burned area, 3 times found in garden, 1 times found in mature dry forest, 1 times found in montane rainforest, ...
Found most commonly in these microhabitats: 62 times at bait, 2 times at bait on ground, 10 times ex sifted leaf litter, 1 times nest in dead stick, 2 times vienna sausage bait, 1 times on ground.
Collected most commonly using these methods: 64 times Baiting, 2 times search, 4 times Winkler, 4 times MaxiWinkler, 2 times MiniWinkler, 1 times at bait, 1 times bait.
Elevations: collected from 20 - 1320 meters, 291 meters average
Type specimens: Holotype Pheidole janzeni: casent0608973; Paratype: fmnhins0000050027, fmnhins0000050028; Paratype Pheidole janzeni: casent0608974, casent0608975, casent0608976, casent0608977, casent0608978, casent0608979, casent0608980, casent0608981, casent0608982, casent0608983, casent0608984, casent0608985, casent0608986, casent0608987, casent0608988, casent0608989, casent0608990, casent0608991, casent0608992, casent0608993, casent0608994, jtlc000007093, jtlc000007094