Solenopsis metallica

During collections in Parana´ state in 2015, we observed that S. metallica presents a less aggressive response and sting to nest disturbance than Solenopsis invicta and other fire ants. It appears much more shade tolerant than S. invicta as it builds nests underneath closed canopy. (Pitts et. al. 2018)

Identification
Pitts et. al. (2018) - Head broad, cordate. Head sculpture with large piligerous foveolae, 0.01–0.03 mm in diameter. Median frontal streak present. Median ocellus absent. Scape long, almost reaching the vertex of the head. Mandibular costulae well developed throughout entire length. Mesonotum with 30–36 setae. Promesonotal suture in largest major workers angulate medially, sometimes projecting upward. Propodeum sculpture glabrous posteroventral to spiracle. Postpetiole shape as high as or higher than broad. Postpetiole sculpture in posterior view with lower 0.25–0.33 transversely rugose, upper surface glabrous and shiny; first gaster sternite with anterior projections, visible in dorsal view.

Apart from its usual bright orange or goldish appearance to the naked eye, the major workers of this species are easily distinguished from others in this species-group by the long scape failing to reach the vertexal margin of the head, postpetiole sculpture in posterior view with lower 0.25–0.33 transversely rugose, upper surface glabrous and shiny and the anterior projection on the first gaster sternite visible in dorsal view. Other distinguishing characters are present on the gyne, including the greatly diverging clypeal carinae, the large piligerous foveolae on the head and mesosoma, the strongly to weakly defined striae between the ocelli, the lack of a median cell due to the loss of the m-cu cross vein, and the reduction in postpetiolar sculpturing.

The major workers of S. metallica can be easily differentiated from their putative sister species, Solenopsis weyrauchi. Solenopsis metallica have 10–12 costulae on the mandible that are obsolescent medially and have larger piligerous foveolae on the head and mesosoma. In comparison, the major workers of S. weyrauchi have 5–6 complete mandibular costulae and their cephalic foveolae are smaller. The shape of the postpetiole of the workers is most similar to that of Solenopsis saevissima, but is more coarsely sculptured. The darker colored workers appear bicolored, which is similar to the color pattern of Solenopsis electra. The minor workers of this species are usually lighter than the majors, but can sometimes have similar coloration. They also have large, distinct foveolae on the head and mesosoma, which is easily noticed. As with the other fire ant species, however, the minors are difficult to identify. The larvae of this species are unremarkable and are similar to S. saevissima and Solenopsis invicta by having bifid setae on the head capsule. The setae on the head capsule are longer in this species, however, than in S. invicta or S. saevissima.

Distribution
Pitts et. al. (2018) - The type series of the species was originally collected in the highlands of Santa Catarina state, southern Brazil. Further examination of material collected in Rio de Janeiro State in 2008 and Misiones Province in 2015 also proved to be S. metallica, suggesting a southeastern Atlantic Forest range for the species. In 2015, extensive collections in Parana State showed that the species is widely distributed in subtropical humid forest in the region.

Distribution based on Regional Taxon Lists
Neotropical Region: Brazil.

Biology
Pitts et. al. (2018) ' The taxonomic distinctiveness of S. metallica is also circumstantially supported by genetic data. DNA sequence data (mitochondrial: Shoemaker et al. 2006; Ross et al. 2010; nuclear: Gotzek et al. 2007; Krieger and Ross 2005) and a large panel of microsatellite and allozyme data (Ross et al. 2010) clearly distinguish individuals of this species (alternately termed S. sp. “A”, “southern highlands”, or “S. altipunctata” in those studies) from other fire ant species.

Nomenclature

 *  metallica. Solenopsis metallica Pitts, Camacho, Gotzek, McHugh & Ross, 2018: 331, figs. 16–20, 44, 89 (w.q.m.l.) BRAZIL.

Worker
Head: Cordate, slightly longer than broad, widest posterior to eyes, sides weakly convex. Posterior border of head with concave median impression, concavity 0.5X as wide as distance between apices of frontal lobes. Lower edge of anterior border of clypeus bearing large median seta borne on weakly developed median tooth, tooth is absent in some specimens. Clypeal carinae, strongly developed, divergent distally, projecting as triangular teeth that are notably larger than median tooth and much larger than paracarinal teeth. Paracarinal teeth reduced in some specimens. Carinal and paracarinal teeth more dorsally on clypeal border than median tooth. Mandible with normal curvature, four teeth, and 10–12 fine costulae, weakly developed or obsolescent medially, apically becoming broader with shallower intercostular furrows on upper surface. Eye ovate, with maximum diameter 10–12 ommatidia, and minimum diameter 6–7 ommatidia. Scape curved basally, thickest subapically. Apex of scape in repose not surpassing posterior border of head.

Mesosoma: Anterodorsal pronotal border, weakly convex. Anterolateral pronotal corners variously rounded, never distinctly angulate and bearing slight humeral bosses. Promesonotal suture angulate medially with small dorsal projection at apex. Pronotum with steep anterior declivity distinguished from dorsum with slight break in outline at point of anterior mesonotal projection. Metanotal impression conspicuous, set off by steep, coarsely striate, posterior mesonotal and anterior propodeal declivities. Propodeum with dorsal face slightly convex, curving evenly into declivous face. Propodeum angulate posterolaterally due to slight longitudinal, posterolateral bosses. Mesopleural katepisternum defined dorsally by finely striate impression, weakly defined in some specimens.

Metasoma: Petiolar peduncle notably to slightly shorter than base of node. Postpetiolar node globular to subrectangular with dorsum convex, lateral faces straight, parallel to convergent ventrally. Postpetiole, as seen from behind, with height greater than width.

Pilosity: Composed of yellow setae. Longer setae curved. Mesonotum usually with 30–36 erect setae. Mesopleuron with several dorsal setae. Longest setae on metasomal dorsum usually at least 3–4X length of shortest. Suberect pubescence present on cervical flange of pronotum, on anterior face of petiolar nodes, and on propodeal dorsum.

Sculpturing: Integument with distinct piligerous foveolae present on head, mesosoma and petiole, 0.01–0.03mmin diameter (conspicuous even in minors). Piligerous foveolae conspicuous but smaller on legs. Interstitial area smooth, shiny. Sculpture of metapleuron consisting of longitudinal striae. Posterior face of petiole with striae on basal 0.25. Posterior face of postpetiole with transverse striae on basal 0.25, upper 0.75 glabrous with several conspicuous piligerous foveolae.

Coloration: Color varies from yellow-orange with brown metasoma and with T1-T4 lighter anteriorly to brown-red dorsally with ventral portion of head and legs orange, and T1 with apical margin orange. Some specimens with darker medial portions of leg segments. Median streak present, but faint in some specimens.

HL 1.14–1.31, HW 1.00–1.24, SL 0.91–1.06, EL 0.17–0.20, PW 0.59–0.70, DML 1.48–1.70, CI 0.90–0.95, SI 0.80–0.86, REL 0.14–0.16, N=21, (HL 1.21, HW 1.14, SL 0.94, EL 0.18, PW 0.62, DML 1.61, CI 0.94, SI 0.83, REL 0.15).

Queen
Gyne.—Head: Broader than long, quadrate, wider dorsal to eyes than ventrally, sides of head convex from eyes to occipital angles, curving inwards to mandibular base. Eye sometimes with 1–4 setae protruding from between ommatidia, setae ≤ 3X length of ommatidium. Ocelli small. Median ocellus circular to slightly elliptical; lateral ocelli ovate, smaller than median ocellus. Clypeus projecting, carinal teeth stout and sharp, carinaewell defined, less so dorsally, greatly divergent ventrally. Paracarinal teeth small, sometimes poorly defined. Median clypeal tooth poorly developed to absent. Approximately 0.33% of eye dorsal to midpoint of head.

Mesosoma. Narrower than head, robust, ovate. Parapsidal lines present on posterior 0.50 to 0.75 of disk. Mesonotum without posteromedian furrow. Median bidentate process present on metasternum.Wing venation, m-cu cross vein absent, medial cell open.

Metasoma. Lateral faces of postpetiole strongly to slightly concave. Petiolar spiracle tuberculate in some cases.

Coloration, Sculpturing, and Pilosity. Piligerous foveolae large, width 0.01–0.03 mm in diameter, larger on head than on thorax and abdomen. Pubescence simple, yellow and erect, longer and denser on head than elsewhere, longest on anterior edge of clypeus. Mesosoma with longest pubescence (length >0.30 mm) 2X longer than shortest pubescence. Mandible with 7–8 coarse, distinct costulae present throughout entire length. Propodeum with fine striae posteriorly, anterior 0.25% polished. Petiolar node with 0.25 coarsely striate, remainder polished. Lower 0.25 of posterior face of postpetiole granulate to striato-granulate, upper 0.75% of surface polished. Area between ocelli coarsely striate, sometimes drastically so. Interfoveolar spaces on head finely striate. Remaining integument smooth and polished. Color orange with black mesonotal maculations present anteromedially and around parapsidal lines. Dorsal transverse band dark brown on pronotum and mesopleuron. Metasoma dark brown, except petiole ventrally and basal 0.25% of T1 and S1 orange blending to dark brown apically. Leg segments orange, brown medially. Sometimes T1 base completely dark brown. Internal margins of ocelli dark brown.

L ~6.1–6.4, HW1.30–1.40,VW0.80–0.85, HL 1.10–1.15, EL 0.31–0.36, OD 0.19–0.22, OOD 0.16, LOW 0.04–0.06, MOW 0.07–0.09, CD 0.19–0.22, MFC 0.13–0.15, EW 0.29–0.36, SL 0.90–1.01, PDL 0.14–0.16, LF1 0.08–0.11, LF2 0.07–0.10, LF3 0.07–0.10, WF1 0.05–0.08, FL 1.10–1.20, FW 0.19–0.30, MW 1.15–1.31, DLM 2.34–2.51, PRH 0.93–1.10, PL 0.60–0.70, PND 0.55–0.65, PH 0.55–0.65, PPL 0.25–0.35, DPW 0.50–0.65, PPW 0.66–0.74, PHB 0.34–0.44, N=2.

Male
Head. Trapezoidal. Eye very large, strongly convex, ovate, occupying more than 0.5X side of head, anterior border not reaching insertion of mandible. Ocelli large, prominent. Anterior edge of clypeus convex. In lateral view, clypeus shows small, blunt, beak-like central lobe directed anteriorly. Mandible linear, with two large teeth. Antennal scape ;1.3X as long as broad, cylindrical. Pedicel subglobose, broader than scape or following flagellomere.

Mesosoma. Robust, elliptical. In lateral view, mesonotum flat, at the same level as the pronotum. Scutellum swollen and strongly convex, higher than mesonotum. Propodeum rounded, basal face strongly convex transversely, only slightly convex longitudinally, declivous face flat and perpendicular. Posterior margin of metapleuron separated from propodeum by a suture and ventralmargins of metapleuron fused to propodeum. Wing venation similar to the male of S. invicta.

Metasoma. Anterior face of petiole gently sloping, posterior face parallel. In lateral view, postpetiole globulose, wider than petiole. Dorsum of petiole with a strong median longitudinal impression, forming two lateral lobes. Petiole anteroposteriorly flattened, bilobate. Postpetiole wider than petiole, ventral surface flat. Postpetiolar spiracles high, strongly projected laterally. Genitalia as in S. invicta.

Coloration, Sculpturing, and Pilosity. All sculpture lacking except for basal 0.25 of petiole and postpetiole, metapleuron and sides of propodeum finely striate and punctuated. Body smooth and polished. Setae golden, suberect, distributed all over the body. Mesonotal pubescence absent. Color black except legs and gaster brown. Wings and veins light brown.

L ~5.44, HW 1.02, VW 0.52, HL 0.8, EL 0.44, OD 0.11, OOD 0.12, LOW 0.11, MOW 0.12, CD 0.29, MFC 0.26, EW 0.35, SL 0.12, SW 0.11, PDL 0.08, PEW 0.14, LF1 0.21, LF2 0.15, LF3 0.17, WF1 0.08, FL 0.41, FW 0.23, MW 0.96, DML 2.4, PL 0.6, PND 0.5, PH 0.43, PPL 0.48, DPW 0.62, PPW 0.72, PHB 0.51, CI 1.28, OI 0.79, REL 0.55, OOI 1.09, VI 0.52, FCI 0.25, CDI 0.36, SI 0.12, SI2 0.27, SI3 0.8, FI 0.56, NI 0.83, PLI 0.72, PHI 0.89, PWI 1.03, PPWI 1.5, PPWB 1.41.

Larva
Fourth instar worker larva.—Head. Large, subpyriform in anterior view (height 0.43 mm, width 0.45 mm). Cranium slightly broader than long. Antenna with 2 or 3 sensilla, each bearing spinule. Occipital setal row with 7–8 bifid setae, base 0.5–0.8X total length of seta, setae 0.07–0.16 mm long. First setal row on vertex with 2 bifid setae, base;0.66X total length of seta, 0.10 mm long. Second setal row on vertex with 4 setae, inner 2 setae simple, outer 2 setae with bifid apices (base ;0.66X length), 0.10–0.15 mm long. Setae ventral to antenna level simple, 0.15–0.17 mm long. Clypeus with row of 3–4 setae, inner setae shorter than outer setae, 0.05–0.10 mm long. Labrum small, short (width 2X length). Labrum with 4–5 minute sensilla and 2 setae on dorsal surface of each half and apical border with 3–6 sensilla on each half. Labrum with 2–3 coarse isolated spinules near each ventrolateral corner. Straight medial portion of mandible with 2–5 teeth that decrease in size dorsally. Maxilla with apex conical, palpus peg-like with 5 sensilla, each bearing one spinule. Galea conical with 2 apical sensilla, each bearing one spinule. Labium with patch of spinules dorsal to each palpus, spinules coarse and isolated or in short rows of 2–3. Labial palpus slightly elevated with 5 sensilla, each bearing one spinule.

Body. Spiracles small, first spiracle larger than others. Body setae of 2 types. Simple setae (0.05–0.10 mm long) arranged in transverse row of 6–9 on ventral surface of each thoracic somite and on each of 3 anterior abdominal somites, some with short denticulate tips. Bifid setae (0.06–0.09 mm long) occur elsewhere, base 0.5X length.

Length. Approximately 2.6–2.8 mm.

Type Material
Paratypes
 * Brazil: Santa Catarina State, Rt.166 ca 22 km north of Santa Cecilia, Serra Geral, 1200 m, .xi.1998, K. G. Ross, M. C. Mescher, D. D. Shoemaker, and L. Keller [MZSP: 1 worker, G-83, USNMENT01126729], [DZUP: 1 worker, G-84, USNMENT01126730], [EMUS: 1 worker, G-84, USNMENT-01126731], [UGCA: 1 worker, G-83, USNMENT01126732].
 * Brazil: Parana State, Edge of Ponto Grossa, median of Rt.PR-513, 20.xi.2015, G. Camacho and D. Gotzek, n. PR15-084 [USNM: 1 male, USNMENT01126733; 1 gyne, USNMENT01126734].

Etymology
This species is named for one of its most common and conspicuous color morphs, the bright, metallic orange phase. It is also one of several authors’ favorite rock bands. The specific epithet is a noun in apposition.

Determination Clarifications
Gotzek et al. (2007) used the name Solenopsis altipunctata , referencing a manuscript name for this species. That name was thus rendered unavailable.