Strumigenys margaritae

In Trinidad Mark Deyrup and Lloyd Davis observed workers of S. margaritae mingled in a foraging column of Wasmannia auropunctata moving along a piece of plastic irrigation pipe on an open hillside each morning for three consecutive days. Returning to the site two years later, Lloyd Davis (personal communication) found this mixed foraging column still occurring. (Deyrup and Cover 1998)

Strumigenys margaritae is an infrequently collected non-native (Neotropical) ant that has established along a wide southern USA swath (Ivanov et al. 2019; Bolton 2000). This species is collected over a wide range of habitats but is often found in more arid sites such as prairie remnants, scrub, and grassy areas –predicting further spread throughout other more western states with similar habitats (Mississippi Entomological Museum 2020). Strumigenys margaritae has often been collected using sweep nets off low vegetation (Mississippi Entomological Museum 2020). Although observed to forage above ground, it appears S. margaritae nests in the ground from limited observations. According to the few USA collections from flight traps (n=4 from Louisiana and Mississippi) mating flights occur between July and August. I found a nest in an open pasture-edged woodland near Athens, Georgia, in mid-September, and males and alate queens were still present. In addition, Strumigenys subnuda is a rarely collected social parasite thought to be associated with S. margaritae. Although not collected in Texas, it occurs in Louisiana and there is no reason to think it might not also co-occur with S. margaritae elsewhere. (Booher, 2021)

Identification
Bolton (2000) - A member of the Strumigenys schulzi-group. The entirely densely sculptured first gastral tergite seen in margaritae is shared only with the Peruvian Strumigenys pholidota. However, in margaritae the first sternite is also weakly sculptured, standing hairs are present on the first gastral tergite, the head lacks dense longitudinal rows of appressed scale-like hairs, the mandibles and scapes are longer (compare measurements), and the dentition is quite different.

Strumigenys margaritae was the only species of this group known to occur north of Mexico. Strumigenys subnuda was described in 2010 from queens collected in Mississippi and Louisiana. In the U. S. A. margaritae has been recorded from Alabama, Florida, Georgia and Texas (M. R. Smith, 1931; Brown, 1953a; Brown, 1964; D. R. Smith, 1979; G. C. Wheeler & J. Wheeler, 1985; Deyrup, Johnson, et al., 1989).

Longino (Ants of Costa Rica) - Mandibles in side view straight, not broadly curved ventrally; mandibles relatively short, subtriangular, much of the apical portion meeting along a serially toothed masticatory margin when closed (former Smithistruma); leading edge of scape with a row of conspicuous projecting curved hairs, of which those distal to the subbasal bend distinctly curve toward the base of the scape; pronotal humeral hair absent; dorsal surfaces of middle and hind tibiae with decumbent to appressed short spatulate hairs; color red-brown; face punctate; sides of posterior half of mesosoma completely and densely punctulate; ventral petiolar spongiform appendages entirely obsolete; disc of postpetiole sculptured; gaster with more than 10 erect, somewhat spoon-shaped setae; propodeal teeth slender and acutely tapered, their infradental lamellae obsolete and represented only by fine carinae; basal tergite of gaster finely striolate-punctulate over entire surface, with no or very short coarse striae at postpetiolar insertion.

Distribution
This species has been introduced into Florida. It is a rare species known from a few sites in north Florida: Marion, Leon, Okaloosa and Escambia counties. Pest status: none. First published Florida record: Deyrup et al. 1989; earlier specimen: 1983. (Deyrup, Davis & Cover, 2000.)

USA to Suriname and most Caribbean Islands; in eastern USA from Florida to Virginia, west to Missouri; in western USA occurs in Oklahoma and Texas (Booher, 2021).

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Anguilla, Antigua and Barbuda, Bahamas, Barbados, Belize, British Virgin Islands, Colombia, Costa Rica, El Salvador, Greater Antilles, Grenada, Guadeloupe, Guatemala, Honduras, Lesser Antilles, Mexico, Netherlands Antilles, Panama, Puerto Rico, Saint Lucia, Trinidad and Tobago.

Biology
Longino (Ants of Costa Rica) - I rarely encounter this species because I tend to concentrate my collecting in forested habitats. I have never obtained it by sifting litter. In a study of ant visitors to extrafloral nectaries of Passiflora pittieri at Sirena, Corcovado National Park, I observed many species of ants on thousands of shoots on hundreds of plants. Among these observations, I observed margaritae only twice, both times on shoots of one plant. In another study, collecting ants in scrubby roadside vegetation along the road to Monteverde (120m, La Pita), I found specimens of margaritae in sweep net samples. Finally, I found a worker while collecting in a city park in the middle of San Jose, the capital city of Costa Rica.

Brown (1953) - According to H. H. Smith (in Forel, loc. cit. 1893), margaritae is a rather common ant on St. Vincent, usually nesting in the sod layers covering rocks. The colonies at this locality were estimated to contain up to 250 individuals. One of the nests "as taken in an open place at the foot of a tree. In Alabama, Mr. Wilson took the two solitary dealate females in October and November, and also captured a stray worker from leaf litter. Dr. Goodnight found this species in soil samples in Chiapas. Thus it appears that margaritae docs not share the arboreal tendencies by other similar species with large, protruding eyes and other characters which would seem to fit it for life in epiphytes.

Atchison & Lucky (2022) found that this species, as expected, does not remove seeds.

Nomenclature

 *  margaritae. Strumigenys margaritae Forel, 1893g: 378 (w.q.m.) ANTILLES. Combination in S. (Cephaloxys): Emery, 1924d: 325; in S. (Trichoscapa): Smith, M.R., 1947f: 587; in Smithistruma: Smith, M.R. 1951a: 827; Brown, 1953g: 108; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 123. See also: Bolton, 2000: 221.

Worker
Bolton (2000) - TL 1.9-2.1, HL 0.52-0.58, HW 0.36-0.42, CI 69-73, ML 0.10- 0.12, MI 17-20, SL 0.26-0.30, SI 68-72, PW 0.24-0.26, AL 0.48-0.56 (10 measured).

Counting from base of mandible teeth 1, 3, 5, and 7 are narrow and acute, and relatively high; teeth 2, 4, and 6 are blunt apically and each is only half the height of the preceding tooth. First gastral tergite conspicuously densely sculptured everywhere, densely striolate-punctulate to shagreenate with superimposed dense striolae. Basigastral costulae very short and inconspicuous, restricted to extreme base of tergite and frequently masked by the prevalent tergal sculpture. First gastral stemite also sculptured but less strongly so, usually finely shagreenate to punctulate at least basally and laterally. Remainder of body finely densely reticulate-punctate on every surface. Apicoscrobal hair and pronotal humeral hair absent. Cephalic dorsum behind highest point of vertex without a transverse row of standing hairs. Cephalic ground-pilosity of curved narrowly spatulate hairs; between level of frontal lobes and highest point of vertex these hairs mostly directed medially. Standing hairs entirely absent from dorsal alitrunk but ground-pilosity of curved spatulate hairs distinct. Posteriorly curved or inclined short standing hairs, that are thickened apically to weakly remiform, are present on first gastral tergite. Eyes large, with 5-6 ommatidia in the longest row. Propodeum armed with a pair of narrowly triangular spines, each subtended by a very narrow lamella that may be reduced to a mere carina. Base of first gastral sternite in profile sometimes with a curved transverse carinula but without a pad of spongiform tissue.

Type Material
Bolton (2000) - Syntype workers, queens and males, ANTILLES IS: St Vincent I., Palmyra Estate, 1000 ft, 3.xi.; Golden Grove Estate, 500 ft, ix.; Hermitage Estate, Cumberland Valley, 1000 ft, 2.xii. (all coll. H. H. Smith) [examined].

References based on Global Ant Biodiversity Informatics

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