Solenopsis macdonaghi

Other than a few specimen label details regarding habitat, gallery forest edge and Campo cerrado, this species' biology is unknown.

Identification
Pitts et. al. (2018) - A member of the Solenopsis saevissima species-group. Superficially, the lighter gynes of S. macdonaghi look most similar to Solenopsis interrupta and Solenopsis metallica in coloration. However, the coloration does differ by being a somewhat duller yellow orange in S. macdonaghi. Also, the S. macdonaghi gynes lack the large piligerous foveolae on the head and mesosoma, along with interfoveolar striae, which are characters present in S. interrupta and S. metallica. The gynes of these three species also differ slightly to greatly in sculpturing of the postpetiole and can be normally distinguished by this character.

Trager (1991) reported that the heads of S. macdonaghi gynes are typically broader than other species, but this observation was based on a limited number of specimens. Additional measurements have shown this not to be the case.

The males of S. macdonaghi closely resemble other species, but they, along with Solenopsis saevissima, are among the largest males. The males of S. macdonaghi look most similar to Solenopsis quinquecuspis in size, shape and coloration. Although males of S. macdonaghi are normally less coarsely sculptured than S. quinquecuspis, the males of these two species are not easily distinguished. Males of S. macdonaghi are also very similar to Solenopsis megergates, but the CI for males of S. macdonaghi is somewhat smaller than for S. megergates.

The larva of S. macdonaghi is distinct from that of S. saevissima in that it has bifid setae on the head capsule. The larva of S. macdonaghi is virtually indistinguishable from that of S. megergates and S. quinquecuspis, despite the smaller body size and the longer base of the body setae in S. macdonaghi.

Distribution
Pitts et. al. (2018) - Solenopsis macdonaghi is found throughout the floodplains of eastern Argentina and western Uruguay. Several records exist for Paraguay. Trager (1991) reports a population at Cochabamba, Bolivia but this is far removed from the known range of S. macdonaghi and, in fact, may represent an introduction.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Paraguay.

Nomenclature

 *  macdonaghi. Solenopsis saevissima var. macdonaghi Santschi, 1916e: 379 (w.q.) ARGENTINA. Junior synonym of interrupta: Creighton, 1930b: 89. Revived from synonymy and raised to species: Trager, 1991: 179.

Pitts et. al. (2018):

Worker
Head broad, cordate. Head sculpture with small piligerous foveolae, approximately 0.01 mm in diameter. Median frontal streak absent. Median ocellus in largest major workers present. Mandibular costulae obsolescent, except apically, rarely complete. Mesonotum with 20–25 setae. Promesonotal suture in largest major workers angulate medially, sometimes projecting upward. Mesonotum in lateral view weakly convex. Propodeum sculpture glabrous posteroventral to spiracle. Propodeum in largest major workers curves upward from metanotal groove higher than flattened posterior portion, appearing as anterior raised portion in lateral view. Postpetiole shape much broader than high. Postpetiole in posterior view lacking transverse rugae or with rugae medially, normally granulate to dorsum. Color generally red yellow to brown yellow, gaster dark brown, T1 with red yellow to brown yellow maculation.

Queen
Head. Slightly wider than long, quadrate, sides of head convex from eyes to occipital angles, straight to nearly straight ventral to eyes. Eyes sometimes with 3–4 setae protruding from between ommatidia, setal length ≤3X width of ommatidium. Ocelli large, prominent. Median ocellus circular, lateral ocelli slightly ovate. Clypeus projecting, carinal teeth stout and sharp, carinae well defined, slightly divergent ventrally, edge of clypeus between carinae with shallow concave depression, depression deepest between carinal teeth. Paracarinal teeth small, indistinct. Median clypeal tooth poorly developed, usually absent. Approximately 0.50 of eye dorsal to midpoint of head.

Mesosoma. Parapsidal lines present on posterior 0.50 of disk. Mesonotum with indistinct, median furrow present on posterior 0.25 or less. Bidentate median process present on metasternum. Wing venation as in Fig.

Metasoma. Lateral faces of postpetiole straight to weakly convex. Petiolar and postpetiolar spiracles tuberculate in some cases.

Coloration, Sculpturing, and Pilosity. Piligerous foveolae small, sparse, width <0.01 mm in diameter. Pubescence simple, golden and erect, longer and denser on head than elsewhere, longest on anterior edge of clypeus. Mesosoma with longest pubescence (length >0.30 mm) 3X longer than shortest pubescence. Mandible with 10–12 fine, distinct costulae present throughout. Propodeum with fine striae throughout. Petiolar nodewith lower 0.75 of surface finely striate, dorsum polished. Postpetiole node with striations on lower 0.75 of surface somewhat coarser, 7–9 striae, finely granulate, dorsum polished. Remaining integument smooth and polished. Color varies from orange to dark orange and legs orange to yellow orange with T1-T4 brown laterally and apically. Basal orange coloration of T1 blends evenly to brown apically. Mesonotum maculations absent on parapsidal lines, although sometimes present anteromedially. Internal margins of ocelli not dark brown. Median frontal streak absent.

L ~6.9–7.5, HW 1.42–1.46, VW 0.85–0.92, HL 1.22–1.34, EL 0.41–0.46, OD 0.12–0.15, OOD 0.23–0.25, LOW 0.08–0.11, MOW 0.10–0.14, CD 0.15–0.17, MFC 0.18–0.20, EW 0.30–0.34, SL 0.95–1.05, PDL 0.21–0.25, LF1 0.10–0.14, LF2 0.07–0.11, LF3 0.07–0.09, WF1 0.07–0.09, FL 1.20–1.25, FW 0.26–0.27, MW 1.35–1.45, DLM 2.48–2.84, PRH 1.02–1.09, PL 0.73–0.82, PND 0.54–0.70, PH 0.65–0.70, PPL 0.32–0.38, DPW 0.65–0.70, PPW 0.70– 0.75, PHB 0.35–0.40, N=7.

Male
Head. Eyes normally with 2–4 setae protruding from between ommatidia, setal length ≤ 3X width of ommatidium. Ocelli moderate to large, prominent, elliptical.

Mesosoma. Propodeum rounded, declivous face perpendicular, flat except with distinct to indistinct median longitudinal depression, basal face strongly convex transversely and longitudinally. Metapleuron not broad, ~0.66 as wide as high. Wing venation as in Fig.

Metasoma: In cephalic view, dorsum of node with deep median depression, bilobate. Petiolar and postpetiolar spiracles distinctly tuberculate to not tuberculate. Genitalia as in Figs.

Coloration, Sculpturing, and Pilosity. Pubescence short, thin, yellow, erect to suberect and of uniform length over body (0.25–0.30 mm), longest on gena and vertex. Mesonotal pubescence dense. Propodeum with base striato-granulate, medially finely granulate. Area between eye and insertion of antenna, pronotum posteriorly and base of petiolar node coarsely granulate. Posterior surface of postpetiolar node granulate throughout. Area between ocelli and vertex finely striato-granulate to granulate. Areas anterolateral to median ocellus usually glabrous. Gena coarsely granulate, less often rugose anterior to occipital carina, never rugose throughout. Metapleuron and lateral faces of scutellum striato-granulate. Remaining integument smooth and polished. Color red brown to black, antennae and legs yellow brown. Mandibles yellow, extreme apex brown.

L ~5.7–6.6, HW 1.00–1.20, VW 0.34–0.39, HL 0.74–0.89, EL 0.40–0.52, OD 0.08–0.11, OOD 0.15–0.28, LOW 0.10–0.18, MOW 0.13–0.16, CD 0.16–0.22, MFC 0.13–0.18, EW 0.34–0.41, SL 0.14–0.18, SW 0.09–0.11, PDL 0.05–0.08, PEW 0.12–0.15, LF1 0.20–0.24, LF2 0.12–0.15, LF3 0.14–0.18, WF1 0.07–0.10, FL 0.95–1.30, FW 0.15–0.22, MW 1.35–1.62, DLM 2.28–2.80, PRH 0.80–1.10, PL 0.55–0.65, PND 0.50–0.60, PH 0.43–0.63, PPL 0.25–0.34, DPW 0.50–0.74, PPW 0.54–0.79, PHB 0.20–0.29, N=10.

Larva
Fourth instar worker larva.—Head. Large, subpyriform in anterior view (height 0.47 mm, width 0.54 mm). Cranium slightly wider than long. Antenna with 2 or 3 sensilla, each bearing spinule. Occipital setal row with 6–8 setae, median pair simple otherwise bifid, base 0.5–0.66 X total length of seta, 0.06–0.10 mm long. First setal row on vertex with 2 denticulate to simple setae, 0.10–0.11 mm long. Second setal row on vertex with 4 simple setae, 0.10–0.13 mm long, rarely denticulate. Setae ventral to antenna level simple, 0.12–0.16 mm long. Clypeus with transverse row of 4 setae, inner setae shorter than outer setae, 0.10–0.11 mm long. Labrum small, short (breadth 2X length). Labrum with 4–6 sensilla and 2 setae on dorsal surface of each half. Apex with 4–6 sensilla on each half. Each half of epipharynx with 2–3 isolated sensilla. Straight medial portion of mandible with 2–5 teeth that decrease in size dorsally. Maxilla with apex conical, palpus peg-like with 5 sensilla, 1 bears spinule. Galea conical with 2 apical sensilla bearing spinules. Labium with patch of spinules dorsal to each palpus, spinules in 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 (0.06–0.12 mm long) arranged in transverse row of 6–10 on ventral surface of each thoracic somite and on each of 3 anterior abdominal somites, some with short denticulate tips. Bifid setae (0.09–0.14 mm long) occur elsewhere, base 0.66X length. Bifid setae on thoracic dorsum with shorter bases.

Length. 3.4-3.5 mm.

Type Material
Syntype workers, gynes. Argentina. Entre Rios. Estacion Sosa. MacDonagh. .

References based on Global Ant Biodiversity Informatics

 * Santschi F. 1916. Formicides sudaméricains nouveaux ou peu connus. Physis (Buenos Aires). 2: 365-399.
 * Santschi F. 1925. Fourmis des provinces argentines de Santa Fe, Catamarca, Santa Cruz, Córdoba et Los Andes. Comunicaciones del Museo Nacional de Historia Natural "Bernardino Rivadavia" 2: 149-168.
 * Trager J. C. 1991. A revision of the fire ants, Solenopsis geminata group (Hymenoptera: Formicidae: Myrmicinae). Journal of the New York Entomological Society 99: 141-198
 * Wild, A. L. "A catalogue of the ants of Paraguay (Hymenoptera: Formicidae)." Zootaxa 1622 (2007): 1-55.