Pogonomyrmex coarctatus Mayr 1868
Pogonomyrmex coarctatus Mayr, 1868: 170 (worker). Syntypes
examined: 2 workers [NMW], ARGENTINA, Buenos Aires: Bahía Blanca (Strobel leg.); Mayr, 1887: 614
(queen); Bruch, 1917: 303, figs. 1, 2 (male). See also Gallardo, 1932: 150,
figs. 33-36 (NMW worker here designated LECTOTYPE).
Pogonomyrmex coarctatus Mayr var. striaticeps Emery, 1906: 157
(worker, in footnote). Syntypes examined: 3 workers [MACN],
#1609, ARGENTINA, Santa Fe: Rosario (Hubrich leg.); Kusnezov, 1951: 253 (synonomy
under coarctatus;
here confirmed). See also Gallardo, 1932: 156, figs. 37-38 (MACN worker here
designated LECTOTYPE).
Pogonomyrmex coarctatus race bruchi Forel, 1913: 217 (worker).
Syntypes examined: 3 workers [MHNG], ARGENTINA,
Buenos Aires: Bahía Blanca, Puerto Militar (Ingenieur Zelenka leg., 19
November, 1913), 2 workers [MHNG], Buenos Aires: Estación
Verónica, south of La Plata (Schuel
leg.), 1 worker [MLPA], Buenos Aires (MHNG worker from Bahía Blanca here
designated LECTOTYPE).
Pogonomyrmex bruchi Forel; Forel, 1914: 268. Raised to species. See also Gallardo, 1932:
157, fig. 39. NEW SYNONOMY
Worker
Diagnosis. Within the P. coarctatus-group, the combination of: (1)
strongly polymorphic with supermajors, (2) very fine
longitudinal rugae covering most of head, areas
lacking rugae weakly shining to shining, (3) in side
view, lateral lobe of clypeus not enlarged with wide gap between clypeal lobe
and frontal carina (gap width similar to width of antennal scape),
(4) interrugal spaces on mesosoma
weakly to moderately granulate, weakly shining, (5) weak to moderately strong rugae on posterior surface of petiole (6) rugae on dorsum of postpetiole
lacking or with weak rugae near posterior margin, (7)
inferior propodeal spines lacking or very reduced in
size, broadly rounded, and (8) body mostly concolorous
reddish-orange to reddish-brown uniquely characterize this species.
Measurements
– lectotype (n
= 41). HL 3.37
(1.94-3.54); HW 3.66 (1.97-3.99); MOD 0.63(0.39-0.63); OMD 0.74 (0.42-0.94); SL
1.79 (1.28-2.10); PNW 1.97 (1.28-2.29); HFL 2.77 (1.75-2.90); ML 3.27 (2.20-3.54);
PW 0.84 (0.43-0.95); PPW 0.98 (0.64-1.20). Indices: SI 48.91 (51.13-67.50); CI 108.61 (100.50-115.31);
OI 17.21 (13.93-21.61); HFI 75.68 (71.57-91.88).
Description. Highly
polymorphic with supermajors. Head shape varies with worker size, quadrate
in minors, increasingly wider than long in majors and supermajors
(CI = 100.5–115.3, positively associated with head width, n = 42, R2 = 0.69, P
< 0.0001); posterior margin concave medially in full-face view. Longitudinal cephalic rugae
very fine and dense, covering part to most of head but often indistinct, width
of rugae and interrugae
similar; in full-face view median rugae not diverging
toward posterior corners of head. Vertex weakly striate, weakly shining to smooth and shining. Cephalic interrugal spaces and most of
dorsum weakly shining to shining.
Anterior margin of clypeus flat to weakly concave;
dorsal surface with several moderately coarse, subparallel,
longitudinal, oblique, or arc-shaped rugae. In side view, lateral lobe of clypeus not
enlarged with wide gap between clypeal lobe and frontal carina (gap width similar
to width of antennal scape). Numerous long, curved, bristle-like,
yellowish macrochaetae project
from anterior margin of clypeus and ventral side of mandibles. Mandible with six teeth; mandibular
dorsum strongly striated. MOD ranging from 0.15-0.23x HL. Eyes in profile situated anterior to middle
of head, OMD = 1.00-1.58x MOD. Antennal scapes
short (SI = 48.91-70.92), extending beyond posterior margin of eye by less than
length of first two funicular segments. Base of antennal scapes
smooth and shining, distal portion sometimes weakly granulate or weakly
striate, weakly shining to shining; basal flange well developed with carinate margin. Psammophore moderately well developed.
Mesosomal profile
slightly to moderately convex; all mesosomal
surfaces with prominent coarse, subparallel, slightly
wavy to irregular, widely spaced rugae. In dorsal view, humeral portion of pronotum weakly rounded to knoblike. Dorsum of promesonotum with longitudinal rugae
that diverge anteriorly toward humeral angles;
transverse rugae on anterior face of pronotum continue obliquely or longitudinally on pronotal sides; rugae on mesopleura angle posterodorsally. Superior propodeal
spines moderately long, acuminate, connected by well-defined keel; spine length
less than width between bases; regular to slightly wavy transverse rugae on propodeal dorsum
traverse ventrally or anteroventrally on sides. Inferior propodeal
spines lacking or very reduced in size, broadly
rounded. Propodeal spiracles narrowly ovate. Interrugal spaces
on mesosoma moderately granulate, weakly shining. Legs smooth weakly granulate, weakly shining
to smooth and strongly shining.
Petiolar peduncle about
0.7x as long as petiole, anteroventral
margin with broadly rounded process. In
side view, posterior surface of petiole weakly convex; petiolar
node asymmetrical with anterior surface shorter than posterior surface, apex of
node rounded to ovate. In dorsal view,
petiole longer than wide, sides subparallel, slightly
wider near middle, narrowing to spatulate to rounded
anterior margin. Sides
and posterior surface of petiole mostly smooth or with weak to moderately
coarse, wavy to irregular, transverse, oblique, or longitudinal rugae, weakly shining. Dorsum of postpetiole
convex in profile; in dorsal view, widest near posterior margin, narrowing to
anterior margin, maximum width about equal to length; weakly to moderately
granulate-punctate, occasionally with weak transverse
rugae near posterior margin, weakly shining. Dorsum of gaster smooth, moderately coriarious, weakly shining to shining.
Erect white to yellowish pilosity sparsely to moderately abundant on head, mostly
similar in length and arising from foveae; longest hairs not exceeding MOD, few
exceeding 0.5x MOD. Moderately
abundant suberect pilosity
on scape; abundant decumbent hairs on funicular
segments. Legs
with moderately abundant suberect to decumbent setae. Mesosoma with
moderately dense erect setae that are mostly similar in length, longest
approaching MOD; petiole, postpetiole, first gastral tergum with moderately
dense erect setae that are mostly similar in length, longest notably shorter
than MOD; long hairs on margins of posterior gastral terga often longer than MOD. Body mostly concolorous reddish-orange to reddish-brown.
Queen
Diagnosis. As in worker diagnosis, but with
caste-specific morphology of the mesosoma related to
wing-bearing, presence of small ocelli on the head,
and as illustrated in Figure x. This
caste is diagnosed by: (1) large size (HW > 3.65 mm), (2) head mostly lacks fine cephalic rugae,
and (3) inferior propodeal spines poorly developed, wider
than high, broadly rounded.
Measurements - (n = 12). HL 3.35-3.61; HW 3.69-4.06; MOD 0.55-0.64; OMD 0.69-0.86; SL
1.79-2.09; PNW 2.21-2.49; HFL 2.42-2.89; ML 3.73-4.29; PW 1.01-1.20; PPW
1.37-1.49. Indices: SI 45.43-55.03; CI
107.93-114.87; OI 14.21-16.93; HFI 61.42-74.04.
Male
Diagnosis. This caste is diagnosed by: (1) hairs on head
(especially posterior to eyes) and dorsum of mesosoma
moderately long and flexuous, longest rarely exceeding 0.5-0.8x MOD, (2) hairs
on kapepisternum relatively short, length of most
hairs < 0.3x MOD, (3) at least one and usually both mandibles with
three teeth, and (4) superior propodeal spines
usually consisting of a weak crest.
Measurements (mm) - (n = 12). HL 1.70-2.04; HW 1.79-2.05; MOD
0.58-0.73; OMD 0.19-0.36; SL 0.44-0.57; HFL 2.05-2.45; ML 3.21-3.78; PW
0.72-0.80; PPW 0.88-0.99. Indices: SI 23.23-29.38; CI 99.50-110.00; OI 32.22-36.87; HFI
103.02-131.11.
Additional material examined. ARGENTINA: Buenos Aires: Reserva Otamende, 50’, Jan. 21, 1999; Nov. 13, 2003 (CASC; CSC; RAJC);
Tandil, Nov. 20, 1959 (LACM; MACN); Bahía Blanca, Jan. 3, 1964; no date (MACN; MHNG;
MZUSP; NMW); Medanos, Feb. 4, 1938 (MLPA); San Jose Libertad, no date (MACN; MLPA); Azul, Apr. 26, 1962 (USNM); Rosas, no date (USNM); Sierra Bayas,
no date (LACM; MACN); Punta Picada, no date (MACN);
Puerto Militar, no date (MACN); Punta Piedras, no date (MACN); Sierra de la
Ventana, Nov. 19, 2005; no date (CSC; MACN; MCZ; MLPA); Colonia Suarez, Mar. 1920
(MACN); Tres Arroyos, Mar. 31, 1938 (MLPA); Monte Hermoso, no date (MACN; MLPA);
no loc., no date (MACN; MLPA); Rt 33 at 14 km N Bahía
Blanca, Nov. 20, 2005 (CSC); 15 km SE Olavarria, Nov. 18, 2005 (CSC); 32 km S Pehuajó,
Nov. 19, 2005 (CSC). Córdoba: Rt 9 at 6.5 mi E Bell Ville, 390’, Dec. 21, 2005 (CSC; RAJC); Nono, 2940’, Jan. 17, 2008
(RAJC); Rt 20 at 1.0 km N Nono, 2920’, Jan. 23, 2006
(RAJC); Rt 9 at 3.5 km E Marcos Juárez, 330’, Jan.
14, 2010 (RAJC); Alta Gracia La Granja, Sierras Córdoba, no date (MACN); Unguillo, no date (MLPA); no loc., no date (MACN). Entre
Rios: Gualeguay, no date (MACN); Diamante,
Mar. 29, 1918 (MACN); San Jose
de Feliciano, Dec. 1972 (MACN); Rt
14 at 5.1 mi N Gualeguychú, 60’, Dec.
17, 2005 (RAJC); Rt 39 at 36.1 km SE Basavilbaso, 160’, Feb. 13, 2010 (RAJC); Estancia Sosa, no
date (MACN; MLPA; USNM); La Picada, May 24, 1951 (MCZ;
MZUSP; USNM); 10.3 km S Jct Rts
14 & 39, 60’, Dec. 17, 2005 (RAJC); Jct Rts 14 & 130, 70’, Dec. 18, 2005 (CASC; MCZ; RAJC); Rt
16 at 6.1 km E Larroque, 190’, Jan. 13, 2010 (RAJC); Rt 14 at 13.0 km N Ubajuay, 70’, Dec. 18, 2005 (RAJC); Rt 18 at
7.3 mi SW San Salvador, 220’, Dec. 19, 2005 (RAJC); Rt 18 at 20 km E Villaguay, 160’,
Dec. 19, 2005 (RAJC); Villaguay,
200’, Dec. 19, 2005 (RAJC); Rt
18 at 3.3 mi NW Villaguay, 210’, Dec.
19, 2005 (RAJC); Rt 18 at 12.8 mi W Villaguay, 150’, Dec. 20, 2005
(RAJC); Rt 18 at 33.9 mi W Villaguay,
320’, Dec. 20, 2005 (CSC; RAJC); Rt
127 at 2.0 km SW Federal, 230’, Jan. 13, 2011 (RAJC); no loc., no date (USNM). La Pampa: Rt 188 at
28.1 km W Rancul, 950’, Jan. 27, 2008 (RAJC); Monte
Nievas, no date (MACN; USNM); Río Colorado, no date (MACN; MLPA); central La
Pampa, no date (MACN). Rio Negro: 35.6 km NW Jct Rts 251 & 2, 360’, Jan.
22, 2011 (RAJC); Rt 22 at 15 km E Choele
Choel, 400’, Jan. 22, 2011 (RAJC); Rt 251 at 16.6 km N General Conesa,
390’, Jan. 21, 2011 (RAJC); Rt 251 at 9.7 km S
General Conesa, 230’, Jan. 21, 2011 (RAJC); Sauce
Blanco, no date (LACM; MCZ; MZUSP); 51 km E Río Colorado, Nov. 20, 2005 (CSC);
no loc., no date (MACN; MLPA). San Luis: Cortaderas, Jan. 29, 1958
(LACM). Santa Fe: Rt 19 at 14.5 mi W Santa
Clara de Buen Vista, 240’, Dec. 20, 2005 (CSC; RAJC);
Rt 34 at Cañada Rosquín,
230’, Dec. 21, 2005 (CSC; RAJC); Rosario, no date
(MACN); Fives Lille,
no date (MCZ); Saladillo, no date (USNM). URUGUAY:
no loc., no date (MCZ; MLPA; USNM). Lavelleja: Villa Serrana,
Jun. 7, 1961 (USNM). Montevideo:
Montevideo, no date (MACN); near Montevideo, Feb. 20, 1976 (LACM). Locations not found. ARGENTINA: Buenos Aires: Tuzumba, no date (MLPA); Punta dellnolio,
Dec. 1, 1957 (USNM). Rio
Negro: Menatia, Oct. 2, 1914 (MLPA). URUGUAY: Canelones: Crizicon
Falzon, no date (MLPA). Questionable locales (appear to be
outside of geographic range): Catamarca: central Catamarca, no
date (MACN). Mendoza: no loc., no date (MACN).
Etymology. Mayr (1868) did not discuss the naming
of this species, and his reasoning for this name is unclear. The epithet coarctatus (from Latin, coarct = compressed, confined, or drawn close
together, and –atus
= suffix to denote provided with) apparently refers to an unknown structure
that Mayr determined to be compressed or drawn close
together.
Discussion. Pogonomyrmex coarctatus co-occurs
with two other P. coarctatus-group
species, P. lobatus
and P. micans. Pogonomyrmex coarctatus can be distinguished from these two species
based on the following characters: (1) P.
coarctatus has very fine, dense, longitudinal
cephalic rugae that are often indistinct and cover
part to most of head, (2) in lateral view, the lateral lobe of the clypeus is
not enlarged, with a wide gap between the clypeal lobe and frontal carina
(similar to width of antennal scape), (3) dorsum of postpetiole weakly to moderately granulate-punctate, occasionally with weak rugae
near the posterior margin, and (4) body mostly concolorous
reddish-orange to reddish-brown. In P. lobatus, the
head is covered with very fine, dense rugae, and the lateral
lobe of clypeus is massively enlarged, nearly contacting the frontal
carina. In P. micans, the head is covered with very
fine, dense rugae, the dorsum of postpetiole
has prominent moderately coarse transverse rugae, and
workers are bicolored (dark red and blackish). Pogonomyrmex marcusi is only known from mid- to higher elevations of
central Bolivia, and thus is geographically isolated from P. coarctatus;
these two species can be separated using characters in the key.
Pogonomyrmex coarctatus var. striaticeps
was erected because the cephalic sculpturing was more fine and dense than that
on the type specimen (see also
Gallardo, 1932). Kusnezov (1951) synonomized
P. coarctatus var. striaticeps
without discussion. I concur with this synonomy because the degree of cephalic sculpturing in syntypes of P. coarctatus var. striaticeps occurs within colonies of P. coarctatus.
Kusnezov (1951) provided a thorough
discussion on P. bruchi,
indicating that it was closely related to P.
coarctatus, but could be distinguished from the
latter species by its smaller size, but more importantly by its much weaker
degree of worker polymorphism. He also
noted that the geographic range of P. bruchi occurred within that of P. coarctatus, suggesting two
possibilities: (1) that P. bruchi was a distinct species given that its geographic
range was entirely contained within that of P.
coarctatus, and (2) that P. bruchi was an insignificant variety of
P. coarctatus
in the event that the two taxa lacked morphological
differences.
In his key to South American Pogonomyrmex,
Taber (1998) noted that P. coarctatus
and P. bruchi
also differed in the size of the trough at base of the scape
(conspicuous in P. coarctatus,
absent to weak in P. bruchi),
the thickness of the femur on the foreleg (weakly incrassate in P. coarctatus,
strongly incrassate in P. bruchi), and in the keel between the superior propodeal spines (keel lacking in P. coarctatus, keel present in P. bruchi). Cuezzo and Claver (2009) used these same characters
to separate P. coarctatus
and P. bruchi.
I have
examined syntypes of P. coarctatus and P. bruchi, and there are no differences
between these taxa.
None of the characters discussed by Taber (1998) differ consistently between
the two taxa, and variation that he noted occurs
within colonies of P. coarctatus. Thus, I place P. bruchi
as a junior synonym of P. coarctatus. Moreover,
erecting P. bruchi
as a distinct species likely resulted from collecting few specimens and/or not
examining nests to determine if the workers were polymorphic.
REFERENCES
Taber, S.W. (1998) The
World of the Harvester Ants. College Station: Texas A&M University
Press.