Pseudomyrmex concolor

A wide ranging species associated with Tachigali plants.

Identification
Ward (1999) - The worker and queen of this species can be distinguished from all other members of the viduus species group, except Pseudomyrmex insuavis, Pseudomyrmex malignus and Pseudomyrmex penetrator, by the short, broad funicular segments (worker FLI < 1.42, queen FLI < 1.51, and regression of (LF1 + LF2 + LF3) on HW lying below that of other species), posterolaterally expanded frontal carinae, and palp formula of 4, 3. P. concolor differs from P. malignus by the presence of several to (usually) many erect hairs on the sides of the head, by the ventrally deflected and laterally rounded median clypeal lobe, by the narrower petiole (worker PW12 0.58–0.66 versus 0.65–0.69 in P. malignus), and usually by the occurrence of more conspicuously striolate sculpture on the worker mandible (this last character varies). Workers of P. concolor from Amapa´, northeastern Brazil tend to have the pilosity on the sides of the head reduced, but the striolate mandibular sculpture is very well developed and in sharp contrast to the smooth mandibles of ''P. malignus. P. concolor is very close to P. insuavis and P. penetrator, differing from the former species by its narrower petiole (worker PWI 0.74–0.90, versus 0.92–1.04 in P. insuavis) and from the latter by its lighter orange colour (see P. penetrator'').

There is considerable variation in sculpture and pilosity among different populations of P. concolor. Workers from northeastern Brazil (Amapa) are perhaps the most distinctly differentiated; they tend to have a shinier integument, reduced head pilosity on the sides of the head, and less dense pubescence on abdominal tergite IV.

Distribution
Widely distributed in the central and eastern Amazon basin and adjacent Guianas.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil, French Guiana, Guyana, Suriname.

Biology
Ward (1999) - Invariably associated with plants in the genus Tachigali. Wheeler (1921a, 1942) discussed the habits of P. concolor at Kartabo, Guyana (under the name Pseudomyrma damnosa). He described the colonization of Tachigali paniculata Aublet saplings by colony-founding queens of P. concolor, as well as those of Pseudomyrmex malignus and Azteca species; reported their association with pseudococcids (Dysmicoccus brevipes (Cockerell) and Trionymus petiolicola (Morrison)); noted the eventual domination of larger trees by single—but polygynous—colonies; and presented a fascinating set of observations on the larger guild of Tachigali-associated insects at Kartabo. Studies by Fonseca (1993, 1994; Fonseca & Benson, 1995; Fonseca & Ganade, 1996) near Manaus, Brazil have revealed additional details about the biology of P. concolor. In the population near Manaus colonies occupy smaller trees (up to 7m height) of Tachigali myrmecophila (Ducke) Ducke and T. poeppigiana Tulasne (cited as T. polyphylla), in whose domatia the ants tend pseudococcids of the genus Cataenococcus. Although the ants patrol the leaf surfaces of the host plant and aggressively remove herbivores, most of the colony’s food appears to be derived from the coccoids. This is consistent with an earlier report from Guyana of coccoid remains in larval food pellets (Bailey, 1923:37). In a sample of 16 colonies Fonseca (1993) found colony sizes ranging from 22 to 1104 workers (1 to 8 dealate queens), and he provided evidence that colony size is strongly constrained by the amount of nesting space available in the host plant. Other host plant records from museum specimens include Tachigali paniculata (Rio Yatua, Venezuela) and numerous Tachigali unidentified to species.

Pacheco and Del-Claro, 2015 (abstract): Nestmate recognition is fundamental to colonial cohesion in social insects, since it allows altruistic behavior towards relatives, recognition of intruders, territorial monopoly and resources defense. In ants, olfactory cues is a key factor in this process. Pseudomyrmex concolor is a highly aggressive ant that defends their host plant Tachigali myrmecophila against herbivores. However, this defense depends on the ant ability to discriminate in order to treat differentially between members of their own colony and intruders. In this study we investigated "whether" and "how" P. concolor recognizes nestmates from non-nestmates. We hypothesized that P. concolor is skillful in recognizing nestmates and tested it in field with experiments using nestmates and non-nestmates. Additionally, to test the efficiency of resident ants against intraspecific competition during colony foundation, we simulate the plant occupation by a competitor queen, introducing non-nestmates queens in plants previously occupied by P. concolor. For the issue of the "how", we hypothesized that the main cue used by this ant in nestmate recognition is olfactory signal. Thus, we tested adaptive threshold model, which predicts that, if the individual odor and colony's internal template are discrepant enough, the resident nestmate will behave aggressively towards incoming individuals. In this case, we confined nestmates with non-nestmates odors, and then, we reintroduced them in its host plants. In each experiment the frequency of aggressive behaviors were recorded and compared. Results showed that P. concolor recognize and discriminate nestmates from non-nestmates workers (biting and stinging them) and exclude potential competitors queens. Workers reintroduced in their own colony after impregnated with non-familiar odor were treated as non-nestmates. The adaptive threshold hypothesis was confirmed, the main cue used by this ant species in nestmate recognition is olfactory signals.

Pacheco and Del‐Claro (2018) studied how P. concolor defends the host tree Tachigali myrmecophila from herbivores, concluding the ants serve as a defensive biotic agent. This Amazonian canopy tree hosts nests of this ant in its hollow leaf rachis and petioles. The ants in turn have been shown to greatly reduce herbivory on the plants they inhabit. This study experimentally demonstrated the detection of herbivory by the ants significantly increased the number of individuals on experimentally treated leaflets and was more pronounced during foliar damage and foliar extract tests.

Nomenclature

 *  concolor. Pseudomyrma concolor Smith, F. 1860c: 70 (q.) BRAZIL. Combination in Pseudomyrmex: Kempf, 1961a: 400. Senior synonym of latinoda (and its junior synonym damnosa): Ward, 1989: 435; of endophyta: Ward, 1999b: 487.
 * latinoda. Pseudomyrma latinoda Mayr, 1878: 877 (w.) BRAZIL. Combination in P. (Latinoda): Enzmann, 1944: 62; in Pseudomyrmex: Kempf, 1961a: 406. Senior synonym of damnosa: Kempf, 1961a: 406. Junior synonym of concolor: Ward, 1989: 435.
 * endophyta. Pseudomyrma latinoda var. endophyta Forel, 1912g: 22 (w.) BRAZIL. Combination in Pseudomyrmex: Kempf, 1961a: 400. Raised to species: Ward, 1990: 484. Junior synonym of concolor: Ward, 1999b: 487.
 * damnosa. Pseudomyrma damnosa Wheeler, W.M. 1921f: 139, fig. 13 (w.q.m.) GUYANA. Junior synonym of latinoda: Kempf, 1961a: 406.

Worker
Ward (1999) - Measurements (n=16). HL 0.97–1.24, HW 0.86–1.11, MFC 0.107–0.149, LHT 0.67–0.91, CI 0.86–0.95, REL 0.35–0.39, REL2 0.39–0.45, FCI 0.10–0.14, SI 0.40–0.43, FLI 1.04–1.41, FI 0.38–0.44, PLI 0.80–1.00, PWI 0.74–0.90, PPWI 1.35–1.65.

Relatively small species (HW <1.12, LHT <0.92). Basal margin of mandible with small mesial tooth (often worn), closer to the apicobasal tooth than to the proximal tooth (MD4/MD5 approximately 0.65–0.75); masticatory margin of mandible with five teeth, the fourth tooth (counting from the apex) often very weak and abraded. Palp formula 4,3. Median clypeal lobe laterally rounded (not angulate), its anteromedial surface deflected ventrally. Frontal carinae merging anteriorly with the antennal sclerites, well separated at this point (by more than basal scape width), diverging even further posteriorly so that PFC/ASM > 1.10, and sometimes converging slightly again before becoming obsolete. Median lobe of antennal sclerite not conspicuously exposed, partly due to the aforementioned lateral expansion of the frontal carinae (PFC/ASD 0.73–0.88; FCI2 0.66–0.83). Scape relatively short (SI < 0.44), expanded distally to about twice its basal width; funiculus short, also expanded apically, the terminal segment about 1.7–1.9 times the width of the first segment; funicular segments 3–10 conspicuously broader than long (FLI < 1.42). Eye small (REL < 0.40, REL2 < 0.46), only moderately elongate (OI 0.59–0.66). Head a little longer than broad (CI > 0.85), the sides weakly convex, rounding relatively abruptly into the posterior margin, which is flat or very slightly concave, in frontal view. Mesosoma dorsum more or less flattened, but with a deeply incised metanotal groove (MP 0.035–0.063, MPI 0.041–0.062). Dorsal face of propodeum flat to somewhat convex; dorsal and declivitous faces of Propodeum subequal in length (PDI 0.91–1.07), and meeting at a well rounded angle. Metapleural gland bulla well-developed and conspicuous. Petiole slightly longer than high (PLI ≤ 1.00), without a differentiated anterior peduncle in lateral profile; flat anterior face of petiole rising to a summit well behind the midpoint of the petiole (NI 0.60–0.69), then rounding into the steep posterior face. Anteroventral petiolar process well developed, either rounded or with a blunt posteroventral angle. In dorsal view, the minimum (anterior) width of petiole more than half the maximum width (PWI3 0.51–0.59), and the straight sides of the petiole diverging only moderately. Postpetiole globular, notably broader than long (PPWI > 1.34); postpetiolar sternite protruding ventrally; anterior to this a forward-directed anteroventral process is present. Mandible with scattered punctulae on a smooth background, overlain by variable amounts of fine striolation which dulls the reflectance. Dorsum of head mostly smooth and shiny (a weakly coriarious background is developed on the lower half in some workers), with a variable density of punctulae (about 0.010–0.015mm in diameter); such punctulae usually separated by less than their diameters on lower portion of head between compound eyes and antennal insertions, and by one to several diameters between the compound eyes, except for a median strip in which the punctulae are less dense and are accompanied by a few scattered coarser punctures. Punctulae becoming sparser towards the vertex, especially above the compound eyes where they are largely replaced by a few scattered, larger, piligerous punctures; area immediately above eyes shiny and unsculptured. Mesosoma dorsum with numerous punctulae (separated by one to several diameters) on a smooth, shiny background; side of mesosoma with punctulae less well defined and with a tendency toward the development of weak corarious-imbricate sculpture, with a corresponding dulling of the integument, especially on the propodeum laterally. Dorsum of petiole and postpetiole largely smooth and shining, with scattered fine punctulae. Abdominal tergite IV sublucid, the reflectance subdued by fine punctulae and associated appressed pubescence. Standing pilosity common and conspicuous on most of body (MSC 26–47, HTC 6–12); at least six, and usually many more, erect setae visible in outline on either side of the head in frontal view. Appressed pubescence also well developed on most of body; appressed hairs short and inconspicuous on the head, longer and denser elsewhere, forming a moderately dense mat (hairs separated by less than their lengths) on mesosoma dorsum and on abdominal tergites IV and V; pubescence less dense on dorsomedial portions of the petiole and postpetiole where the appressed hairs are separated by more than their lengths. Body uniformly light yellow-brown to orange-brown in colour. Ocellar triangle and femora sometimes lightly infuscated.

Type Material
Ward (1999) :

Holotype (unique syntype) dealate queen, “St. Paul” [Sao Paulo de Olivenca], Amazonas, Brazil [Examined].

Pseudomyrma latinoda Holotype worker, “Amaz.” [Barreiras de Unahan, Rio Purus; see Benson & Setz, 1985:590], Amazonas, Brazil (Trail) [Examined].

Pseudomyrma latinoda var. endophyta Syntype workers, Rio Ariramba, [near] Rio Trombetas (Ducke) [Examined].

Pseudomyrma damnosa Syntype workers, queens, males, Kartabo, Guyana (W. M. Wheeler) and Penal Settlement, Guyana (W. M. Wheeler) One syntype worker in MCZC from Kartabo here designated Lectotype.