Pogonomyrmex eremicus Johnson NEW SPECIES
Holotype worker: ARGENTINA, Mendoza: Departamento
Las Heras, Ruta 39 at 4.1
km S boundary of Parque Nacional
El Leoncito, 32º06.7’S, 69º21.8’W, 7250 feet (2195
m), 31 December 2005 (R.A. Johnson #3727) [MACN]. Paratypes,
same data as holotype: FML
(3w), LACM (3w), MACN (7w, 2 small ergatoid queens),
MCZ (3w), RAJC (7w, 3 small ergatoid queens), USNM (3w).
Additional paratype series, same data as holotype - RAJ#3728: CASC (1w), FML (3w), MACN (9w), RAJC
(6w, 4 small ergatoid queens), UCDC (3w); Ruta 39 at 5.1 km S Parque Nacional El Leoncito, 32º7.2’S
69º21.6’W, 7050 feet (2135 m), 18 January 2008, RAJ#4043: RAJC (6w); RAJ#4044:
MACN (3w, 6m), RAJC (3w, 6m); RAJ#4045: RAJC (4w, 1 large ergatoid
q, 4m); RAJ#4046: MACN (3w), RAJC (6w); RAJ#4047: RAJC (6w).
Worker
Diagnosis. Within the P. brevibarbis-group, the combination of:
(1) small size (HW = 1.09–1.60), (2) coloration (bicolored;
mandibles, mesosoma, petiole, postpetiole
amber orange to dark reddish-orange; head orangish-brown
to brown, first gastral tergum
dark brown, (3) large eyes (MOD = 0.32-0.48; OI = 23.81-33.62), and (4) impressed
mesonotal suture uniquely characterize this species.
Measurements
- holotype (n
= 21 paratypes). HL 1.20
(1.09-1.60); HW 1.11 (1.03-1.51); MOD 0.35 (0.32-0.48); OMD 0.35 (0.31-0.44);
SL 1.04 (0.94-1.39); PNW 0.79 (0.71-0.97); HFL 1.10 (1.03-1.62); ML 1.48
(1.46-2.04); PW 0.30 (0.27-0.39); PPW 0.39 (0.36-0.46). Indices: SI 93.69 (83.67-96.46); CI 92.50
(88.00-98.01); OI 31.53 (23.81-33.62); HFI 99.10 (100.00-115.52).
Description. Head elongate
to subquadrate (CI = 88.00-98.01), widest immediately
posterior to mandibles; posterior margin flat in full-face view. Longitudinal cephalic rugae
prominent, widely spaced, slightly wavy to irregular,
in full-face view median rugae not diverging toward
posterior corners of head. In side view, rugae posterior to eyes not
converging to weakly converging near vertex; vertex rugose. Cephalic interrugal
spaces moderately to strongly granulate, dull to weakly shining. Anterior margin of clypeus
flat to weakly concave; dorsal surface with numerous subparallel
longitudinal rugae. Mandible with six teeth; mandibular
dorsum coarsely striated. Moderate number of medium to long, curved, bristle-like, yellow-brown
to brownish hairs project from anterior margin of clypeus and basolateral margin of mandibles. Eyes large, MOD ranging
from 0.23-0.31x HL. Eyes in
profile situated near middle of head, OMD = 0.79-1.17x MOD. Antennal scapes
long (SI = 83.67-96.46), reaching to or surpassing vertex by up to length of
basal funicular segment; antennal scapes weakly to
moderately striate, punctate, weakly shining. Basal flange of scape
flattened, moderately well developed with carinate
margin. Psammophore
moderately well developed, consisting of numerous short to long hairs scattered
across ventral side of head.
Promesonotal profile slightly
convex, metanotal suture weakly to moderately
impressed, propodeum flat. Dorsum of promesonotum
variable, with weak to coarse, irregular longitudinal rugae
that usually diverge anteriorly toward humeral
shoulders or weakly rugoreticulate; sides of pronotum moderately to strongly granulate, dull to weakly shining,
often with irregular longitudinal rugae along
posterior margin. Mesopleura with wavy to strongly
irregular rugae angling posterodorsally. Posterior face of propodeum with transverse to irregular rugae,
coarsely rugoreticulate, or longitudinal rugae that traverse anteroventrally
on sides.
Propodeum with short, strongly tapered,
bluntly acute to acute spines connected by well defined keel; spine length
about 0.5-0.7x distance between bases.
Inferior propodeal spines well developed,
triangular with bluntly acute to acute tip, length approximately 0.5-1.0x that
of superior spines; inferior and superior spines often connected by a ruga. Propodeal
spiracles ovoid to circular. Interrugal
spaces on mesosoma moderately coriarious,
weakly shining to smooth, strongly shining. Legs weakly coriarious, weakly shining to smooth and strongly shining.
Petiolar peduncle about
0.8x as long as petiole, anteroventral
margin usually with triangular tooth-like process. In side view, petiolar
node asymmetrical with anterior surface shorter than posterior surface; apex of
node weakly rounded to angulate, usually weakly
elevated above flattened posterior surface.
In dorsal view, petiolar node longer than wide,
widest near middle, narrowing to bluntly angulate
anterior margin; dorsum and sides moderately granulate to coriarious,
weakly shining. Dorsum
of postpetiole weakly convex in profile; in dorsal
view, widest near posterior margin, narrowing to anterior margin; maximal width
about equal to length; dorsum and sides slightly coriarious,
weakly shining to smooth and shining.
Dorsum of gaster weakly coriarious, shining to smooth and strongly shining.
Erect
yellow-brown to brownish pilosity moderately abundant
on head, most short to medium long, often with one to several longer hairs up
to about 0.75x MOD. Abundant semidecumbent pilosity on scape and decumbent pilosity on funicular segments. Legs with moderately
abundant semidecumbent to decumbent yellow-brown to
brownish setae. Promesonotum,
petiole, postpetiole, gastral
terga with moderately dense, erect, medium to long
hairs, longest about 0.75x MOD; hairs on propodeum less
dense. Bicolored;
mandibles, mesosoma, petiole, postpetiole
amber orange to dark reddish-orange; head orangish-brown
to brown, antennae, first gastral tergum
dark brown, often with an orangish hue, more
posterior gastral terga sometimes
with lighter transverse bands; legs dark brown.
Queen
Diagnosis. Ergatoid. Pogonomyrmex eremicus has two discrete size phenotypes of ergatoid queens; both phenotypes are similar except for eye
size and coloration. Measurements are
given for each phenotype, but both are described in one narrative with
differences noted as appropriate.
Measurements
- (n = 12 small ergatoid
queens). HL 1.20-1.33; HW 1.10-1.22; MOD 0.36-0.42; OMD 0.30-0.36; SL
0.86-1.07;
Measurements
- (n = 4 large ertagoid
queens). HL 1.55-1.77; HW 1.49-1.56; MOD 0.43-0.44; OMD 0.37-0.43; SL
1.22-1.35;
Description. Ergatoid; lacking all morphological structures related to or for inserting wings. In full face view, head elongate to subquadrate (CI = 88.14-96.13), posterior margin flat. Eyes large (OI = 30.51-36.28 for small ergatoid queens; 27.92-29.53 for large ergatoid
queens). Cephalic dorsum with weak
irregular longitudinal rugae, interrugal
spaces moderately to strongly granulate-punctate,
dull to weakly shining; vertex rugose, weakly shining
to shining. Mandible
with six teeth, dorsal surface coarsely rugose. Psammophore poorly
developed, consisting of short to long hairs scattered across ventral side of
head.
All mesosomal surfaces with subparallel,
irregular rugae to moderately rugoreticulate;
interrugal spaces weakly shining to shining. In dorsal view, mesoscutum and mesoscutellum
visible, but suture lacking between these structures and mesopleura.
Propodeum with prominent superior spines, length about 0.5-0.7x width
between bases; inferior propodeal spines
well-developed, triangular, wider than high, with angulate
to acute tip. Petiolar peduncle about as long as
petiole, anteroventral margin with small acute
triangular process. In side view, petiolar node asymmetrical
with anterior surface notably shorter than posterior surface, apex of node angulate, weakly elevated above flattened posterior surface. Posterior surface of
petiole weakly to moderately coriarious, often with
few weak longitudinal or oblique rugae, weakly shining. Postpetiole convex
in profile; in dorsal view, maximum width about equal to length; dorsum smooth
to weakly coriarious, shining; posterior and posterolateral margins weakly to moderately granulate-punctate, weakly shining. Dorsum of gaster smooth, strongly shining. Most body surfaces with moderately abundant suberect to erect, medium-length brownish setae.
Both queen
phenotypes are bicolored. Small ergatoid
queen: mandibles, mesosoma, petiole, postpetiole amber orange to dark reddish-orange; head orangish-brown to brown; legs, first gastral
tergum dark brown, anterior margin of first gastral tergum often more orangish. Large ergatoid queens: bicoloration
less distinct, generally darker in color than small ergatoid
queen; mandibles, mesosoma, petiole, postpetiole dark reddish-orange; head, legs, first gastral tergum orangish-brown to a dark blackish-orange, anterior margin
of first gastral tergum
often more orangish.
Male
Diagnosis.
Measurements
– (n = 12). HL 0.91-1.07; HW
0.79-0.91; MOD 0.38-0.43; OMD 0.13-0.21; SL 0.32-0.61; HFL 0.93-1.45; ML
1.55-1.86; PW 0.27-0.35; PPW 0.36-0.41.
Indices: SI 38.10-67.78; CI 78.50-96.74; OI 42.22-54.54; HFI
108.14-174.70.
Description.
Additional material examined. ARGENTINA:
Mendoza: 7.0 km E Rt 39 on road to Los Berros,
7160’, Jan. 19, 2008 (RAJC); 18.2 km E Rt 39 on road
to Los Berros, 7200’, Jan. 19, 2008 (RAJC).
Etymology. The specific epithet, eremicus (from Latin, eremic = of the desert, lonely), is a geographical adjective derived from
this species apparently being endemic to the Uspallata-Calingasta
Valley, which is an isolated high elevation valley in the Monte Desert that
lies between the Precordillera on the east and the
Andean Cordillera on the west. This valley
has also been referred to as the Eremean District (Roig et al., 2009).
Discussion. Pogonomyrmex eremicus is easily
recognized by its small size, coloration pattern, large eyes, moderately well
developed psammophore, and weakly to moderately
impressed metanotal suture in profile. One undescribed P. brevibarbis-group
species co-occurs with P. eremicus, but
this species is similar to other P. brevibarbis-group species as it is larger and concolorous dark brown, which contrasts with the small, bicolored P. eremicus.
REFERENCES