Pogonomyrmex vermiculatus Emery 1906
Pogonomyrmex vermiculatus Emery, 1906: 157 (worker). Syntypes
examined: 1 worker [MSNG],
Pogonomyrmex vermiculatus var. joergenseni Forel, 1915: 353 (worker). Syntypes
examined: 12 workers [MLPA], 2 workers [MACN], 6 workers [MHNG], 1 worker
[USNM], #284, ARGENTINA, Santa Cruz Province: to the east of Lago Argentina (Jörgensen leg.). Kusnezov, 1951: 253 [synonomy
under chubutensis,
not confirmed here] (MACN worker here designated LECTOTYPE). NEW STATUS
Worker
Diagnosis. First gastric tergite
usually smooth to moderately coriarious, occasionally
with faint striae at base or anterior one-half of tergite. Cephalic interrugae punctate-granulate,
etc.
Measurements
(mm) - holotype (n
= 12). HL 1.49 (1.40-1.63); HW 1.61 (1.42-1.69); MOD 0.35
(0.30-0.37); OMD 0.35 (0.32-0.41); SL 1.27 (1.04-1.35); PNW 1.12 (0.95-1.12);
HFL 1.53 (1.37-1.61); ML 1.82 (1.52-2.01); PW 0.45 (0.37-0.47); PPW * (0.50-0.61). Indices: SI 78.88 (65.09-80.50); CI 108.05
(99.34-106.96); OI 21.74 (18.34-24.03); HFI 95.03 (86.39-103.90).
* =postpetiole missing.
Description. Head subquadrate
to quadrate (CI = 99.34-106.96), broadest just posterior to eye; posterior
margin flat to slightly convex in full-face view. Longitudinal cephalic rugae prominent, in full-face view, median rugae diverging slightly toward posterior corners of head. Vertex rugose, interrugal spaces smooth and shining to weakly granulate,
sub-shining. Cephalic interrugal spaces moderately to strongly granulate,
dull. Anterior margin of clypeus
strongly concave, medial portion incised to depth of lateral lobes, dorsum with
numerous subparallel longitudinal rugae. Mandible with six teeth; mandibular
dorsum coarsely striated. MOD ranging from 0.19-0.25x HL. Eyes in profile situated slightly anterior to
middle of head, OMD = 0.91-1.23x MOD. In
full-face view, eyes protruding slightly beyond lateral margins of head. Antennal scapes (SI
= 65.09-80.50) failing to reaching posterior corner of head by less than length
of basal funicular segment. Antennal scapes with weak longitudinal striae, sub-shining to shining; basal flange well
developed, flattened, partly translucent with carinate
margin. Psammophore
well developed.
Mesosomal profile
convex. In dorsal view, humeral
portion of pronotum enlarged, slightly to distinctly angulate. All mesosomal
surfaces with prominent subparallel irregular rugae, occasionally rugoreticulate
on pronotal sides. Dorsum of promesonotum with longitudinal rugae
that diverge anteriorly toward humeral angles. Irregular rugae on pronotal sides traverse ventrally or posterioventrally;
rugae on mesopleura angle posteriodorsally; irregular transverse rugae
on dorsum of propodeum traverse ventrally or anterioventrally on sides.
Promesonotal suture often slightly to moderately impressed.
Superior propodeal spines well developed,
slightly shorter than width between their bases, connected by a well-defined
keel; inferior propodeal spines well developed,
slightly broader than high, tapering to a slightly blunt to acute tip. Propodeal spiracles narrowly ovate.
Interrugal spaces on mesosoma
smooth and shining to strongly granulate, slightly dull to sub-shining. Legs smooth and shining to
weakly coriarious, sub-shining to shining.
Petiolar peduncle
long, ventral surface with a well developed rounded process. In side view, posterior
face of petiole weakly convex; petiolar node
asymmetrical with anterior surface notably longer than posterior surface, apex subangulate to angulate. In dorsal view, petiole longer
than broad, widest near spatulate anterior margin,
gradually tapering to posterior margin.
Posterior face of petiole with regular to irregular
transverse or obligue rugae. Dorsum of postpetiole convex in side view; in dorsal view, widest at
or near posterior margin, tapering to anterior margin, maximum width and length
about equal. Transverse rugae on dorsum of postpetiole only
slightly finer and denser than those on petiole; interrugal
spaces on petiole and postpetiole smooth and shining
to weakly coriarious, sub-shining. Dorsum of first gastric tergite variable, most commonly smooth and shining to
weakly or moderately coriarious at and near base,
sub-shining (62 of 71; 87.3%), with striae at base (7
of 71; 9.9%), or with striae continuing onto anterior
one-half or more of tergite (2 of 71; 2.8%).
Erect,
short to medium-length, white pilosity moderately
abundant on head, longest occasionally approaching MOD. Moderately abundant suberect to semidecumbent pilosity on scape; abundant
decumbent hairs on funicular segments.
Legs with moderately abundant suberect
to decumbent white setae. Mesosoma, petiole,
postpetiole, and gastric tergites
with moderately dense, erect, white setae, longest on mesosoma
and petiole. Head a dark reddish-brown
to reddish-black, rest of body black except for antenna, mandibles and lateral
lobes of clypeus blackish with a slight reddish infusion; dorsum of promesonotum sometimes with a reddish infusion.
Queen
Diagnosis. As in
worker diagnosis, but with caste-specific morphology of the mesosoma
related to wing-bearing and presence of small ocelli
on the head, except with longitudinal striae present
on the first gastric tergite. The combination of: (1) dark
reddish head and a black body, (2) … uniquely characterize this species.
Measurements
(mm) – (n = 12). HL 1.42-1.83; HW
1.59-1.87; MOD 0.34-0.41; OMD 0.34-0.42; SL 1.16-1.38; PNW 1.24-1.50; HFL
1.47-1.79; ML 2.19-3.01; PW 0.47-0.61; PPW 0.69-0.84. Indices: SI 65.19-78.86; CI 100.55-117.53; OI
18.58-23.27; HFI 85.25-98.16.
Description. As
in worker diagnosis, but with caste-specific morphology of the mesosoma related to wing-bearing and presence of small ocelli on head, except with longitudinal striae present on the first gastric tergite,
and as illustrated in Figure xx.
In full face view, head quadrate to slightly broader than long (CI =
100.55-117.53), broadest just posterior to eyes, posterior margin flat to very weakly
convex. Longitudinal cephalic rugae prominent, wavy; in full-face view median rugae diverging towards posterior corners of head, interrugal spaces moderately granulate-punctate,
sub-shining; vertex rugose, interrugal
spaces smooth and shining. Mandible with six teeth, dorsal surface coarsely rugose. Psammophore
moderately well-developed.
All mesosomal surfaces except pronotal
sides with subparallel, regular to wavy rugae, rugae irregular to rugoreticulate on pronotal sides,
interrugal spaces smooth and shining to weakly
granulate-punctate, sub-shining; superior propodeal spines acuminate, ranging from short and triangular
to moderately well developed, elongate; inferior propodeal
spines moderately well developed, wider than tall, broadly rounded to subangulate. Petiolar
peduncle long, ventral surface with a weak rounded process. In side view, petiolar
node asymmetrical with anterior surface notably shorter than
posterior surface, apex of node subangulate to
angulate. Posterior face of petiole with wavy transverse to oblique rugae, interrugal spaces weakly
granulate-punctate, sub-shining. In dorsal view, postpetiole
slightly wider than long; dorsum with wavy, transverse rugae
that are weaker and more dense than those on petiole, interrugal
spaces weakly granulate-punctate, sub-shining. First gastric tergite striate along base, striae
sometimes extending over anterior one-half of tergite,
dull. Most body surfaces with
moderately abundant suberect to erect, medium-length,
whitish setae, one to two longer hairs along posterior margin of head approach
MOD. Head
reddish-brown, rest of body black, but mesoscutum, scutellum, and first gastric tergite
sometimes with an orangish infusion.
Male.
Diagnosis.
Measurements
(mm) - (n = 12). HL 1.10-1.29; HW
1.16-1.37; MOD 0.42-0.51; OMD 0.13-0.21; SL 0.41-0.52; HFL 1.45-1.81; ML
2.23-2.59; PW 0.48-0.61; PPW 0.68-0.82.
Indices: SI 31.54-40.52; CI 98.35-114.66; OI 33.08-37.23; HFI
114.60-137.12.
Description.
Additional
material examined.
Etymology. In his
description, Emery (1906) indicated that the mesosoma was covered with rugae
that meander irregularly – hence the name vermiculatus (see also
Kusnezov, 1951).
Discussion. Pogonomyrmex vermiculatus is only
known to co-occur with one P. rastratus-group
species, P. carbonarius. Pogonomyrmex vermiculatus can be distinguished from P. carbonarius
based on: (1) its bicolored body (dark red head, rest
of body black), (2) longitudinal striae usually
absent on base of gaster, and (3) irregular
longitudinal rugae on the dorsum of the mesosoma. In P. carbonarius,
the color is uniformly black (rarely with dark reddish coloration),
longitudinal striae cover most of the first gastric tergite, and the longitudinal rugae
on the dorsum of the mesosoma are very regular.
The
identity of P. vermiculatus
has been misunderstood since its description due to the paucity of verified
material combined with the fact that no one examined the syntype
worker (holotype, by monotypy). For example, Kusnezov
(1951) only examined material from
Meseta de las Vizcachas, Santa Cruz Province (#6756), and his description
of P. vermiculatus
followed that of Emery (1906), indicating that fine longitudinal striae were present along the base of the first gastric tergite, with the rest of the tergite
smooth and shiny. Kuznesov
also used “fine longitudinal striae along the base of
the first gastric tergite” to key out P. vermiculatus. Unfortunately, the holotype
is not informative because it is missing the postpetiole
and gaster.
The
description of one syntype worker also resulted in misunderstanding
intra- and internidal variation in characters such as
striae on the first gastric tergite. However, this variation is significant as
material collected during this study shows that within one colony workers can
display a range of states (see above). These
collections also demonstrate that the holotype worker
was not representative because most workers of P. vermiculatus lack striae
along the base of the first gastric tergite (see
above).
Confusion
over the identity of P. vermiculatus continued into recent times, when Snelling
& Hunt (1975) erroneously synonomized two Chilean species, P. semistriata and P. intermedia, under P. vermiculatus without knowing the true
identity of P. vermiculatus. In reality, P. vermiculatus appears to be rare in
Chile, where it is only recorded from the extreme south (Magdallenes
Region), which contrasts with the variable morphology and broad geographic
distribution described by Snelling & Hunt (1975). Other studies have examined foraging and recruitment
biology of P. vermiculatus
in Chile (Medel &
Fuentes, 1995; Torres-Contreras
et al., 2007, 2009); vouchers
from these studies have not been examined, but it is doubtful that P. vermiculatus
was the species investigated because workers were in these studies were collected
in central Chile (Las Chinchillas National Reserve
and Fray Jorge National Park), hundreds of kilometers north of the known
range.
The
lack of material to examine likely resulted in Forel (1913) describing P. vermiculatus var. joergenseni from
workers that were collected at or very near the type locality of P. vermiculatus. Forel was apparently unaware of the proximity
of these type localities given that he compared P. vermiculatus var. joergenseni to P. vermiculatus
var. chubutensis,
but not to P. vermiculatus. This omission may also have occurred because
Forel assumed that striae along the base of the first
gastric tergite were diagnostic for P. vermiculatus. Consequently, P. vermiculatus var. joergenseni and P. vermiculatus var. chubutensis were compared because both
forms were described to have a smooth and shining first gastric tergite (i.e., lacking striae
near the base).
I examined
15 syntype workers of P. vermiculatus var. joergenseni, finding that the first
gastric tergite was not uniform, but rather that
workers varied in a manner similar to that described above for P. vermiculatus: the base of the first
gastric tergite was smooth and shining on seven
workers, weakly coriarious on six workers, with weak
longitudinal striae on one worker, and with
longitudinal striae extending to the mid-section on
one worker.
Gallardo
(1932) was the only study that directly compared P. vermiculatus
and P. vermiculatus
var. joergenseni,
noting that the former form had punctures between the cephalic rugae whereas the latter form lacked depressed punctures
between the cephalic rugae. However, this character also varied among the
syntypes of P. vermiculatus var.
joergenseni, with the degree of interrugal punctures ranging from weak and sub-shining to
strong and dull. Thus, P. vermiculatus var. joergenseni
is synonomized under P. vermiculatus.
REFERENCES