Solenopsis geminata

In general S. geminata prefers to nest in open fields or sunny glades, avoiding the shade of deep woods. The nests are usually irregular, sandy craters of loose construction but sometimes rotten stumps are utilized as nesting sites. The ferocity of this ant is proverbial, for the activity of the workers when disturbed never fails to attract attention, however callous the observer (Creighton 1930).

Identification
A member of the Solenopsis geminata species-group.

Wetterer (2012) - Although S. geminata minors are very difficult to distinguish from minors of related fire ants, large majors have several distinctive cephalic characteristics that make them simple to identify. These include: (1) a disproportionally large, almost square head with parallel sides, (2) a deep longitudinal groove on the front of the head extending from a distinct medial indentation in the vertex, (3) black mandibles, often with all teeth worn off from use, and (4) short antennal scapes extending only about halfway to the occiput in the largest majors.

Distribution based on Regional Taxon Lists
Afrotropical Region: Cameroun, Gabon, Guinea, Liberia, South Africa, United Arab Emirates. Australasian Region: Australia, New Caledonia. Indo-Australian Region: American Samoa, Borneo, Cook Islands, Fiji, Guam, Hawaii, Indonesia, Kiribati, Malaysia, Marshall Islands, Micronesia (Federated States of), New Guinea, Northern Mariana Islands, Philippines, Samoa, Solomon Islands, Tonga, Vanuatu. Malagasy Region: Madagascar, Mauritius, Réunion. Nearctic Region: Canada, United States. Neotropical Region: Barbados, Belize, Bolivia, Brazil, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, French Guiana, Galapagos Islands, Greater Antilles, Grenada, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Lesser Antilles, Mexico, Netherlands Antilles, Nicaragua, Panama, Puerto Rico, Saint Lucia, Suriname, Trinidad and Tobago, Venezuela. Oriental Region: Bangladesh, Cambodia, India, Laos, Nicobar Island, Sri Lanka, Thailand, Vietnam. Palaearctic Region: Canary Islands, China, Greece, Italy, Japan, Republic of Korea.

Biology
Wheeler (1905), Bahamas - very common on New Providence Island wherever there was soil or sand (West Bay, Nassau, Hog Island, Stanley, etc.). It constructs straggling moundlets with many entrances, garners seeds, but still retains its carnivorous instincts, stings fiercely - in short, exhibits all the traits which have gained for it the name of 'hormiga brava' in Cuba and of 'fire ant' in many other localities.

Deyrup, Davis & Cover (2000): There is no reason why a species could not be imported to a place where it is already native. Normally, one would assume that the native population, having evolved adaptive adjustments to the area, would exclude the representatives of the exotic population, or absorb and dilute the small number of immigrants beyond recognition. If, however, the exotic population has undergone natural selection that makes it better able to coexist with humans and take advantage of the resources and habitat modification that humans offer, the exotic population might be favored. Populations of S. geminata have been transported around the World; we have seen specimens from, among other places, a mid-Pacific islet, Johnson Atoll. Some of the confusing variation found among Florida populations could be due to the occurrence of one or more exotic populations overlaid on native populations.

Solenopsis geminata has been observed forming knotted balls of workers clinging to floating wood when their nests are flooded during the rainy season in the Brazilian Pantanal and the Colombian and Venezuelan Llanos (Jaffe, 1993).

Nipitwattanaphon et al. (2020) examined this species in Thailand. They found all examined colonies were polygynous with only a few queens. Queens from the same colonies were highly genetically related. Population structure was partitioned into two clusters. Pairwise FST values revealed very high genetic differentiation between colonies suggesting low gene flow among populations. This result suggests that queens were locally mated and founded colonies by a budding strategy. Isolation-by-distance among local populations was not significant.

Associations with other Organisms
S geminata is parasitized by numerous species of phorid flies.

Porter et al. (2018) studied the fire ant decapitating fly Brown and Morrison (Diptera: Phoridae) and its host specificity. This fly occurs in Texas and neighboring regions of Mexico (Plowes et al. 2009). This fly is 1 of more than 20 species of Pseudacteon decapitating flies known to parasitize tropical fire ants in their native range (Plowes et al. 2009). We found that P. bifidus was not attracted to non-Solenopsis ants presented in the field. Furthermore, no Pseudacteon species known to parasitize Solenopsis fire ants has been observed to parasitize ants in another genera despite extensive field observations.

Worker
Additional images can be found here

Queen
Additional images can be found here

Nomenclature

 *  geminata. Atta geminata Fabricius, 1804: 423 (q.) CENTRAL AMERICA. Roger, 1862c: 289 (w.m.); Mayr, 1867a: 110 (w.q.m.); Wheeler, W.M. 1900b: 21 (l.); Wheeler, G.C. & Wheeler, J. 1955c: 132 (l.); Crozier, 1970: 116 (k.). Combination in Solenopsis: Mayr, 1863: 453. Senior synonym of clypeata, mandibularis: Roger, 1862c: 289; of cephalotes, paleata: Roger, 1863b: 32; Trager, 1991: 163; of glaber, laboriosus, polita: Mayr, 1863: 453; Mayr, 1886c: 362; Trager, 1991: 163; of drewseni: Mayr, 1870b: 996 (footnote); Mayr, 1886d: 460; of coloradensis: Mayr, 1886c: 365; of lincecumii, saxicola: Emery, 1895c: 276; of innota: Wheeler, W.M. 1922a: 877; of nigra: Creighton, 1930b: 59; of laevissima, mellea: Donisthorpe, 1932c: 463, 455 respectively; of rufa (and its junior synonym diabola): Ettershank, 1966: 141; of eduardi (and its junior synonym perversa), medusa (and its junior synonym bahiaensis), galapageia: Trager, 1991: 163. See also: Smith, D.R. 1979: 1386. Current subspecies: nominal plus micans.
 * paleata. Myrmica paleata Lund, 1831a: 116 (footnote) (w.) BRAZIL. Junior synonym of geminata: Roger, 1863b: 32.
 * mandibularis. Solenopsis mandibularis Westwood, 1840b: 87, pl. 2, fig. 5 (w.) "America aequinoctiali". Junior synonym of geminata: Roger, 1862c: 289.
 * rufa. Atta rufa Jerdon, 1851: 106 (w.q.) INDIA. Bingham, 1903: 158 (m.). Combination in Solenopsis: Emery, 1892b: 166. Junior synonym of geminata: Dalla Torre, 1893: 76. Revived from synonymy as subspecies of geminata: Forel, 1899a: 119; Wheeler, W.M. 1915b: 397; Creighton, 1930b: 66. Senior synonym of diabola: Creighton, 1930b: 66. Junior synonym of geminata: Ettershank, 1966: 141.
 * clypeata. Atta clypeata Smith, F. 1858b: 169 (q.m.) MEXICO. Junior synonym of geminata: Roger, 1862c: 289.
 * cephalotes. Solenopsis cephalotes Smith, F. 1859a: 149 (s.w.) INDONESIA (Aru I.). Junior synonym of geminata: Roger, 1863b: 32; of rufa: Creighton, 1950a: 231; of geminata: Trager, 1991: 163.
 * mellea. Myrmica mellea Smith, F. 1859a: 148 (w.) INDONESIA (Aru I.). Junior synonym of geminata: Donisthorpe, 1932c: 455.
 * laboriosus. Crematogaster laboriosus Smith, F. 1860b: 109 (q.) INDONESIA (Batjan I.). Combination in Solenopsis: Mayr, 1863: 453. Junior synonym of rufa: Creighton, 1950a: 231; of geminata: Trager, 1991: 163.
 * laevissima. Myrmica laevissima Smith, F. 1860b: 108 (w.) INDONESIA (Batjan I.). Junior synonym of geminata: Donisthorpe, 1932c: 463.
 * drewseni. Diplorhoptrum drewseni Mayr, 1861: 73 (diagnosis in key) (w.) ITALY. Junior synonym of geminata: Mayr, 1870b: 996; Mayr, 1886d: 460.
 * glaber. Myrmica glaber Smith, F. 1862b: 34 (w.) PANAMA. Junior synonym of geminata: Mayr, 1886c: 362; Trager, 1991: 163.
 * polita. Myrmica polita Smith, F. 1862b: 34 (w.) PANAMA. [Unresolved junior primary homonym of Myrmica polita Smith, F. 1860b: 108 (now in Pheidologeton).] Junior synonym of geminata: Mayr, 1863: 453; Mayr, 1886c: 362.
 * coloradensis. Atta coloradensis Buckley, 1867: 346 (s.w.) U.S.A. Junior synonym of geminata: Mayr, 1886c: 365.
 * lincecumii. Atta lincecumii Buckley, 1867: 344 (s.w.) U.S.A. Junior synonym of geminata: Emery, 1895c: 276.
 * saxicola. Myrmica (Monomorium) saxicola Buckley, 1867: 341 (w.) U.S.A. Junior synonym of geminata: Emery, 1895c: 276.
 * diabola. Solenopsis geminata var. diabola Wheeler, W.M. 1908e: 424 (w.q.m.) U.S.A. Junior synonym of rufa: Creighton, 1930b: 66.
 * nigra. Solenopsis geminata var. nigra Forel, 1908b: 45 (w.) COSTA RICA. Junior synonym of geminata: Creighton, 1930b: 59.
 * eduardi. Solenopsis eduardi Forel, 1912g: 12 (w.) COLOMBIA. Subspecies of geminata and senior synonym of perversa: Creighton, 1930b: 67. Junior synonym of geminata: Trager, 1991: 163.
 * innota. Solenopsis geminata var. innota Santschi, 1915c: 257, fig. 6 (s.w.q.m.) GABON. Junior synonym of geminata: Wheeler, W.M. 1922a: 877.
 * medusa. Solenopsis geminata subsp. medusa Mann, 1916: 447, pl. 4, fig. 31 (w.) BRAZIL. Creighton, 1930b: 69 (q.). Senior synonym of bahiaensis: Creighton, 1930b: 68. Junior synonym of geminata: Trager, 1991: 163.
 * galapageia. Solenopsis geminata var. galapageia Wheeler, W.M. 1919c: 272 (w.q.) ECUADOR (Galapagos Is). Subspecies of geminata: Creighton, 1930b: 65. Junior synonym of geminata: Trager, 1991: 163.
 * bahiaensis. Solenopsis edouardi var. bahiaensis Santschi, 1925d: 237 (w.) BRAZIL. Junior synonym of medusa: Creighton, 1930b: 68.
 * perversa. Solenopsis edouardi var. perversa Santschi, 1925b: 13 (s.w.q.) BRAZIL. Junior synonym of eduardi: Creighton, 1930b: 67.

Type Material


Crematogaster laboriosus

Holotype queen in. Labelled “Bac. 23.”

Myrmica laevissima

Two worker syntypes in. Labelled “Bac. 7.”

Myrmica mellea

Holotype worker in. Labelled “Aru.”

Solenopsis cephalotes

Three worker syntypes (on a single card) in. Labelled “Aru.” (= Aru I. New Guinea).

Two specimens in, labelled by Donisthorpe as syntypes of cephalotes, have “Men.” (= Menado, Sulawesi) as their locality. Smith gives the type-locality as “Aru.” All the specimens, from both localities, appear to be S. geminata (Fabricius).

Worker
Trager (1991) - MEASUREMENTS AND INDICES: HL 1.06-2.20, HWO.98-2.33, SLO.78-1.l4, EL 0.15-0.29, PW 0.57-1.06, AL 1.18-2.08, CI 92-108, SI 47-84, 01 11-16. N = 34.

WORKER DIAGNOSIS. Head (ffv) subquadrate to subtrapezoidal (sides often divergent or flaring anteriorly, especially in specimens from southern Central America and eastern South America), with sides straight to weakly convex and parallel to weakly divergent anteriad (sides weakly convergent anteriad in specimens from southern Texas), often slightly indented just anterior to eyes; posterior border with deep angular median emargination between two nearly hemispherical lobes ("temples"); emargination 1.0-1.5 x as wide as distance between apices of frontal lobes; median clypeal tooth lacking or (rarely) rudimentary; carinal teeth thick at base, strongly protruding, clypeal border between them concave; mandibles thick and strongly curved mesad, especially in largest individuals; mandibular teeth present in all individuals upon eclosion, but often worn off through seed-milling by larger individuals, such that apices dulled or flattened; mandibular costulae complete in smaller majors, to irregular and largely obsolete in larger majors; eye (lv) appearing small relative to hypertrophied head, greatest diameter with 9-11 facets, least diameter with 7-9; largest majors rarely with median ocellus more or less well developed; scapes (ffv) short, curved, scape failing to reach apices of occipital lobes by 0.3-0.5 x SL; pronotum with rounded, at most faintly angular anterolateral corners; promesonotal suture conspicuous, approximately right-angular to weakly obtuse-angular, raised as a small boss at most anterior point; promesonotal profile (lv) formed of 2 convexities meeting at anterior mesonotal boss, pronotal profile more strongly convex and at most feebly angular; anteroventral border of mesopleuron thickened, often bearing one or more spine-like, triangular, lobate or rectangular projecting flanges; metanotal impression marked, set off by a ridge at its juncture with propodeum; propodeal profile more or less diamond-shaped, with dorsum flat to weakly concave; descending though obtuse, carinate angles to weakly convex declivous face; petiolar peduncle as long as or a little longer than base of node; profile of petiolar node cuneate with a relatively sharp crest; postpetiole 1.02-1.08 x as wide as petiole.

Piligerous foveolae of head and thoracic dorsum conspicuous and abundant, 0.025 or more in diameter, those near mouthparts and on sides ofhead sometimes elongate; on larger specimens, mesopleuron largely unsculptured to feebly rugose, but coarsely rugose along pleural suture and near edges of sclerite, especially anteroventrally (in smaller specimens, mesopleuron striate-punctate to coarsely rugose); dorsum of propodeum with a pair of irregular dorsolateral carinae, these best developed at juncture of dorsal and declivous faces; posteriorly, transverse striae or rugae may occur on dorsal, concave surface between carinae; area surrounding propodeal spiracle encircled by coarse, irregular rugosity; declivous face of propodeum with transverse rugae contiguous with those of metapleuron on lower portion, but on upper part more neatly aligned than, and not always contiguous with those on side of propodeum; lateral carinae usually obsolescent on all but uppermost portion of propodeal declivous face; petiolar peduncle transversely striate; base of node areolate-punctate; petiolar ventral process consisting of 1 or 2 small teeth, or rarely, a very narrow, transparent flange; dorsum and anterior face of petiolar node sparsely punctate foveolate, sometimes dorsum with transverse striation like that on posterior face, dorsal margin weakly scalloped; posterior face of petiolar node transversely striate to weakly rugose-areolate below, sparsely sculptured, or less often sculptured as below near top, though less coarsely; sides of postpetiole rugose-punctate; venter of postpetiole dull, coarsely punctate; dorsum ofpostpetiole weakly scalloped, usually shiny and unsculptured or with a weaker version of sculpture below; posterior face of postpetiole transversely rugose-punctate.

Pilosity of head and promesonotum abundant, 0.13--0.37 mm in length; some pilosity often present on meso- and metapleuron.

Color highly variable, though generally fairly consistent within a colony; ranging from concolorous orange-red with only posterior portion of gaster dark brown (var. rufa), to nearly concolorous brownish black with only head near base of mandibles and appendages (especially distally) reddish-brown (var. nigra). Smaller workers tend to be darker and more uniformly colored than bigger ones. Darker S. geminata are possibly limited to or at least prefer more humid microhabitats, and ecological conditions during rearing may be at least partly responsible for adult coloration, but this needs study. Redder variants often are, or at least appear less sculptured than darker forms, but are more likely to have mesopleural flanges. However, I have studied samples from single colonies with virtually the entire range of color and sculpture described above, and S. geminata individuals may have any possible combination of color and sculpture.

Queen
Creighton (1930) - Length 7.5-8 mm.

Head, exclusive of the mandibles, one-sixth broader than long, quadrate, a little wider behind the eyes than in front of them, the sides very feebly convex from the eyes to the occipital angles, straight or nearly straight in front of the eyes and meeting the anterior border of the head at a sharp angle. Occipital angles well-marked, the occiput flat with a narrow and shallow median impression, occipital furrow clearly defined, frontal furrow short, clearly marked only for about half the distance from the median ocellus to the base of the frontal lobes, thereafter becoming shallow and indistinct. Ocelli large and prominent. Clypeus feebly projecting, carinal teeth very stout and rather blunt, the edge of the clypeus between them with a shallow concave impression ; lateral denticles small, often poorly defined and in some cases represented only by a sinuousity in the edge of the clypeus. Mandibles strongly bent but less so than in the major worker, the masticatory border with three large teeth and usually the rudiment of a fourth. Eyes large, strongly convex, irregularly oval in outline, their posterior border reaching a point half way between the occiput and the anterior border of the head. The antennal scape in repose just reaches the lateral ocellus. Funicular joints and club as in the major worker.

Thorax robust, elliptical, its maximum width three-fifths of its length, only slightly narrower than the head (the eyes excluded). Seen in profile the mesonotum shows a straight posterior half and a convex anterior portion which overhangs the pronotum. Scutellum as high as the mesonotum, slightly convex with a short, perpendicular posterior face. Angle of the epinotum well-defined but very obtuse, the basal and declivious faces of about equal length. Mesosternum large and subglobose beneath.

Petiolar nodes very similar to those of the major worker except that the peduncle is thicker, the node of the petiole slightly lower and the postpetiole bears on either side an obtuse, somewhat conical, ventral projection with a small opening at its summit (this condition is sometimes found in the major worker but in that caste the conical projection is usually absent and the opening occurs as a small tubercle on the side of the node). Seen from above the nodes are very strongly transverse and of approximately equal width. Abdomen as in the major worker. Wings hyaline with yellow veins.

Punctures smaller and less numerous than in the major worker. Somewhat larger on the head than on the thorax and abdomen. Body hairs long, golden and erect, somewhat longer on the head than elsewhere, longest on the anterior edge of the clypeus. Mandibles with a few coarse, indistinct striae, epinotuin almost completely covered with fine wavy striae, petiolar nodes, except their summits which are shining, striato-rugulose. For the rest smooth and shining. The color varies from a clear yellowish brown with the front of the head, the mesosternum and the appendages paler and the mandibles and the posterior half of the abdomen castaneous, to a deep castaneous brown with only the extreme anterior portion of the head yellowish brown.

Male
Creighton (1930) - Length 5.8 mm.

Head trapezoidal, its maximum width (including the eyes) approximately one-fourth greater than its length. Eyes very large, strongly convex and oval in outline, occupying more than one-half the. side of the head, their anterior border reaching the insertion of the mandible. Ocelli very large and prominent, the lateral ocelli which mark the boundary of the occiput with a shallow concave impression between them. Anterior edge of the clypeus approximately straight; seen from the side the clypeus shows a blunt, beak-like central lobe. Mandibles small, linear, bidentate. Antennal scape about one and one-half times as long as broad, roughly cylindrical ; first funicular joint sub globose, broader than the scape or the following joint; second funicular joint more than twice as long as broad, third joint one and one-half times as long as broad, the remaining joints all more than twice as long as broad and progressively decreasing in width.

Thorax bulky, elliptical, its greatest width two-thirds of its length, only slightly less than twice as wide as the head (eyes included). Seen from the side the anterior part of the mesonotum is greatly swollen and overhangs the pronotum which is so much displaced that the head of the insect appears to be attached to the ventral surface of the thorax. Epinotum rather rounded, the basal face strongly convex transversely and slightly convex longitudinally, declivious face flat and virtually perpendicular. Node of the petiole in profile low but*with an acute summit, the anterior face not sharply separated from the thick peduncle, the posterior face perpendicular. Seen from behind the summit of the node shows a broad, shallow median impression. Postpetiole in profile as high as the node of the petiole, about one and one-half times as high as long with a long, backward sloping anterior face, a rounded summit and a very declivious posterior face. The conical lateral projections are even stronger than in the female. Seen from above both nodes are very transverse, the postpetiole is approximately three times as broad as long· and one-sixth wider than. he node of the petiole. First gastric segment truncate at the base but not impressed. Wings hyaline, the veins clear yellow.

Punctures fine and fairly numerous, the hairs which they bear long, thin, golden, erect or sub erect and of uniform length over the body, those on the legs shorter and stiffer; antennae without long hairs but clothed with a dense short pubescence. Base of the epinotum, area between the eye and the insertion of the antenna and the area between the ocelli stria to-granulate. Base of the petiolar nodes granulate. For the rest smooth and shining. Color yellowish brown to piceous brown, the antennae and legs pale yellow.