Solenopsis xyloni

This species nests in open areas in soil or under stones, it may build unsightly nests of loose soil on lawns. Reproductives are found in the nest throughout the year, nuptial flights occur from May through September. Flights occur in the afternoon and are usually announced by large numbers of very aggressive ants milling around the nest entrance. These ants are aggressive with a painful sting, although not nearly as aggressive as the introduced red fire ant, Solenopsis invicta. They derive the name “native fire ant” from their sting. The species causes considerable damage to seed banks, kills newly hatched birds, girdles agricultural plants, attacks agricultural products, attacks electrical equipment, and is a serious, stinging kitchen pest. (Mackay and Mackay 2002)

Identification
A member of the Solenopsis geminata species-group.

These ants are often concolorous dark in color, although they are also bicolored with a red head and mesosoma, and a black gaster. The gaster rarely has any light brown areas.

Distribution
In Nevada this species is restricted to the Hot Desert region in the southern tip. Elevation range is from -160 ft. in Death Valley, California to 4500 ft. near Beatty, Nevada (Wheeler & Wheeler, 1986).

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Mexico.

Biology
In Nevada, Wheeler & Wheeler (1986) examined 18 records. Five nests where under stones, 1 under rotten wood, 2 at the base of desert shrubs, 1 in chaff beside a nest of Pogonomyrmex rugosus, 1 in exposed soil with a crack as an entrance. One colony was described as populous and aggressive; the sting was annoying; seeds were found in the nest. Rissing (personal communication) reported that ants of this species raided colonies of Pheidole gilvescens, Pogonomyrmex californicus (numerous), Pogonomyrmex rugosus and Veromessor pergandei (numerous) on his study site in Boulder City, Nevada.

Hill (2007) provides the following notes on a raid by the army ant Neivamyrmex swainsonii:

On 27 June 2006, while on a collecting trip in west Texas, a colony of N. swainsonii was observed raiding a colony of Solenopsis xyloni. These observations were made just outside of Alpine, in Brewster County, Texas (30°20’46”N 103°41’39”W) at 1,548 m, behind a pavilion along a fencerow separating a hotel parking lot and a pasture. The activity occurred in an area measuring approximately 1x1.5 m that consisted of mostly bare soil and gravel with some forbs and Cynodon dactylon (L,) Pers (Poaceae) (Bermuda grass). The observations were made between 7:55 P.M.-9:10 P.M., and the temperature was 28.8°C.

While collections of ants were being made in the area, a large number of S. xyloni were observed, apparently relocating their colony from an old nest site to a new one approximately one meter away. Many N. swainsonii workers were emerging from three holes in the ground between these two locations, whereupon they attacked the S. xyloni workers and took their brood (eggs and pupa). In most cases, the S. xyloni workers only minimally defended their brood, before dropping it and running away. In other cases, the N. swainsonii took the brood from the mandibles of the S. xyloni workers after a brief skirmish. Several S. xyloni workers carrying brood apparently tried to evade the onslaught of their attackers by climbing onto a small forb. When a N. swainsonii worker ventured up the forb, the S. xyloni moved further up the plant until they were at the top. When the N. swainsonii neared them, the Solenopsis dropped their brood, and fell to the ground. The N. swainsonii workers also were observed also attacking male and female S. xyloni alates and carrying them underground after they were subdued. One S. xyloni worker also was observed being carried underground. Additionally, several N. swainsonii workers were seen entering and exiting the S. xyloni colony, but none of those exiting were observed carrying anything.

During the course of these observations, the movement trail of the Solenopsis became more obtuse as the Neivamyrmex pushed further into their ranks. A couple of workers of two other ant species, Pogonomyrmex rugosus and Novomessor cockerelli, were also moving throughout the area. The S. xyloni attacked both of these larger species when encountering them with seemingly greater aggressiveness than they exhibited for the more similar sized N. swainsonii, and in one case were able to kill one of the P. rugosus workers.

The observations ceased near sundown. The next morning the site was visited again, but there was no sign of either the Neivamyrmex or the Solenopsis. It would be interesting to know whether the Solenopsis were already moving their colony at the time and the Neivamyrmex took advantage of their vulnerability, or if the Solenopsis were moving because the Neivamyrmex already had attacked their original colony.

Nomenclature

 *  xyloni. Solenopsis xyloni McCook, 1879: 188, figs. 37, 38 (s.w.q.) U.S.A. Wheeler, W.M. 1915b: 396 (m.); Wheeler, G.C. & Wheeler, J. 1955c: 133 (l.); Taber & Cokendolpher, 1988: 95 (k.). Junior synonym of geminata: Mayr, 1886d: 460; Dalla Torre, 1893: 76. Revived from synonymy as subspecies of geminata: Wheeler, W.M. 1910g: 563; Wheeler, W.M. 1915b: 395. Revived status as species: Creighton, 1930b: 98; Creighton, 1950a: 232; Snelling, R.R. 1963: 9. Senior synonym of maniosa, pylades: Trager, 1991: 166.
 * pylades. Solenopsis geminata r. pylades Forel, 1904d: 172 (q.) MEXICO. Forel, 1909a: 267 (w.); Forel, 1911c: 297 (m.); Bruch, 1916: 315 (m.). Raised to species: Forel, 1909a: 267; Bruch, 1914: 223; Forel, 1916: 459. Subspecies of saevissima: Santschi, 1923c: 267. Junior synonym of geminata: Emery, 1922e: 198; of saevissima: Wheeler, W.M. 1915b: 395; Wheeler, W.M. 1916g: 143; Wheeler, W.M. 1919c: 272; Creighton, 1930b: 70; of xyloni: Trager, 1991: 166.
 * maniosa. Solenopsis geminata subsp. maniosa Wheeler, W.M. 1915b: 396 (w.q.m.) U.S.A. Subspecies of xyloni: Creighton, 1930b: 102. Junior synonym of xyloni: Creighton, 1950a: 232. Revived from synonymy and raised to species: Wheeler, G.C. & Wheeler, J. 1986g: 13. Junior synonym of xyloni: Trager, 1991: 166.