Solenopsis saevissima

A South American fire ant that utilizes disturbed habitats and has been introduced to areas beyond its native range.

Identification
S. saevissima may be easily distinguished from both Solenopsis invicta and Solenopsis richteri by the characters given in the descriptions and figures. The major points in the separation of saevissima from invicta are in the habitus of the head, the thoracic shapes in major workers, the proportions of the postpetiole, the differences in sculpturing, and the differences in color in major workers. S. richteri and saevissima are not likely to be confused because of the strong differences in color. They are also different in many other ways including head shape, thoracic structure, and sculpturing. (Buren 1972)

Distribution based on Regional Taxon Lists
Afrotropical Region: Guinea. Neotropical Region: Argentina, Bolivia, Brazil, Ecuador, French Guiana, Guyana, Paraguay, Suriname, Uruguay.

Habitat
In French Guiana Solenopsis saevissima is found in riparian forest, forest edges, and meadows. Riparian forest is likely its native habitat and this species is commonly found along naturally disturbed riverbanks of the Amazon Basin. Solenopsis saevissima is also able to quickly colonize areas of rainforest disturbed by man. (Dejean et al. 2015)

Associations with other Organisms
S saevissima is parasitized by numerous species of Phorid Flies.

Nomenclature

 *  saevissima. Myrmica saevissima Smith, F. 1855c: 166, pl. 13, fig. 18 (w.) BRAZIL. Combination in Solenopsis: Mayr, 1862: 751. Goni, Zolessi & Imai, 1983: 365 (k.). Junior synonym of geminata: Mayr, 1865: 109; Mayr, 1886d: 460; Dalla Torre, 1893: 76. Revived from synonymy as subspecies of geminata: Wheeler, W.M. 1915b: 395. Revived status as species: Mann, 1916: 447; Santschi, 1916e: 378; Santschi, 1923c: 265; Creighton, 1930b: 80. Senior synonym of gracilior: Creighton, 1930b: 80; of moelleri (and its junior synonyms incrassata, morosa), perfida: Wilson, 1952b: 55. Material of the unavailable name picea referred here by Trager, 1991: 189. Current subspecies: nominal plus itinerans. See also: Buren, 1972: 15; Trager, 1991: 188.
 * gracilior. Solenopsis moelleri var. gracilior Forel, 1904d: 174 (w.) BRAZIL. Junior synonym of saevissima: Creighton, 1930b: 80.
 * moelleri. Solenopsis moelleri Forel, 1904d: 173 (w.q.m.) BRAZIL. Subspecies of saevissima and senior synonym of incrassata, morosa: Creighton, 1930b: 83. Junior synonym of saevissima: Wilson, 1952b: 55.
 * incrassata. Solenopsis geminata var. incrassata Forel, 1908c: 362 (w.) BRAZIL. Subspecies of pylades: Forel, 1909a: 268; of saevissima: Gallardo, 1919b: 247. Junior synonym of moelleri: Creighton, 1930b: 83.
 * morosa. Solenopsis saevissima var. morosa Santschi, 1916e: 380 (w.) BRAZIL. Santschi, 1923c: 265 (q.). Junior synonym of moelleri: Creighton, 1930b: 83.
 * perfida. Solenopsis saevissima var. perfida Santschi, 1923c: 266 (w.) BRAZIL. Junior synonym of saevissima: Wilson, 1952b: 55.

Worker
Buren (1972) - Head length .76 to 1.36 mm, width .64 to 1.37 mm; about 1.27 to 1.36 mm long, and 1.22 to 1.37 mm wide in majors. Scape length 1.00 to 1.04 mm in majors. Thoracic length 1.63 to 1.75 mm in majors.

Head wider behind the eyes as in Solenopsis invicta but lacking the subcordate appearance, occipital lobes not well developed, and occipital excision weak. Sides of head weakly convex, sometimes nearly straight. Scapes reaching or nearly reaching peaks of occipital lobes in majors. Pronotum with weakly to moderately developed shoulders in majors. Promesonotal suture always very weak, even in majors; pronotal surface anteromedially to this suture may be flattened, but never appearing actually sunken as in Solenopsis richteri. Promesonotum in profile rather evenly and moderately convex. Base of propodeum straight or very weakly convex and longer than the declivity. Petiole with a high, ovate scale, usually as wide or nearly as wide as narrow postpetiole; postpetiole little if any wider than long except in larger majors; in posterodorsal view postpetiole in majors with convex anterior border and straight sides. Transverse impression or rear dorsal surface of postpetiole often distinct.

In medium and small sized workers, head wider in front than behind; scapes reaching or surpassing hind borders of head; pronotum without trace of humeri or flattened area; postpetiole small, with sides slightly converging to rear but maintaining approximate equality in length to width ratio.

Sculpture weakly etched, most surfaces smooth and shining; genae with weak, irregular striae in front of eyes; piligerous punctures weak and inapparent on nearly all surfaces; striate area of mesopleura consisting of very fine and usually weakly etched striae, in very large workers these occasionally somewhat obliterated; wide smooth shining areas usually apparent on all sides of propodeal spiracle. Sculpture nearly absent on petiole, rear face of scale appearing free of shagreen throughout the size range. Postpetiole in major workers with subopaque areas on sides caused by minute puncturing; posterodorsal face largely smooth and shining even in majors; some weak transverse punctostriae largely confined to small area behind transverse impression; in very large majors dorsal surface may be somewhat shagreened, a few punctostriae may occur in front of impression.

Pilosity not appreciably different from that of richteri and invicta, possibly a little sparser than in those species.

Colors largely pale to darker yellow or light yellowish brown in medium to large workers; small workers may show considerable infuscation. The color may fade with time in preserved specimens.

Mandibles and often antennae dark brown and distinct from yellowish head; occiput and vertex faintly to more definitely banded with brown. Thorax and large spot on 1st segment of gaster yellowish to yellowish brown in large workers. Remainder of gaster brown. Petiole, postpetiole, and legs usually a little darker in color. Medium and small workers with gastric spot usually absent, thorax and rear third or more of the head considerably darker in some workers. No median dark mark on front of head, contrasting with the condition in invicta.