Strumigenys eggersi

An unusual Dacetine in its tolerance for inhabiting relatively dryer habitats.

Identification
Bolton (2000) - A member of the gundlachi-complex in the Strumigenys gundlachi group. Among the species closest related to Strumigenys gundlachi, eggersi is isolated by the characters in its description. It separates from Strumigenys denticulata, with which it shares the characters of extreme reduction or absence of postpetiolar appendages, by its shorter mandibles (MI 58 - 65 as opposed to MI 72 - 85 in denticulata), presence of a pair of standing hairs anteriorly on the pronotum, and more strongly sculptured gaster. Pyramica eggersi and P. gundlachi are the only species of the gundlachi-group to have been recorded from the U.S.A., where they are apparently restricted to Florida (Brown, 1960a; D. R. Smith, 1979; Deyrup, Johnson, et al., 1989).

Longino (Ants of Costa Rica) - Mandibles in full-face view linear, elongate and narrow; leading edge of scape with freely projecting hairs; inner margin of mandible without a tooth or distinctly enlarged denticle at or near the midlength; labral lobes short, trigger hairs at apices of lobes long; apical fork of mandible small, with two tiny intercalary denticles; mandibles straight, with weakly convex inner borders, each bearing 4-8 minute denticles on distal 1/3 to 1/2; spongiform appendages of petiole and postpetiole obsolete; first gastral tergum superficially reticulate-punctulate and opaque in front, becoming indefinitely shagreened and weakly shining behind.

Distribution
A common species in Florida, where it has been introduced, as far north as Union County. Pest status: none. First published Florida record: Brown 1960. (Deyrup, Davis & Cover, 2000.)

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Barbados, Belize, Bolivia, Brazil, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, Greater Antilles, Guatemala, Haiti, Honduras, Lesser Antilles, Mexico, Paraguay, Peru, Puerto Rico, Saint Lucia, Trinidad and Tobago, Venezuela.



Biology
Deyrup (1997) - Among the snap-trap ants this is an unusually drought-tolerant species that also thrives in disturbed conditions. The queens are often relatively abundant, giving the impression that this species lives in small colonies that produce many new queens that can found new colonies. This would be a useful adaptation for living in frequently disturbed habitats, where occupied nest sites are often destroyed and new ones created.

Caribbean
Brown (1960) - Weber found specimens in a compost heap in the Botanical Garden at Roseau, Dominica, and in an island of vegetation growing in the Pitch Lake of Trinidad; also on Trinidad, he took a sample from low-growing epiphytes in second-growth forest. Kempf sifted specimens from humus in Sao Paulo. Indications are that this species can stand more dryness than many dacetines, and its presence in many culture areas suggests that it is spreading rapidly through nursery stock transport and other human commerce.

Costa Rica
Longino (Ants of Costa Rica) - In Costa Rica this species appears rare, although my collecting has not emphasized dry and/or synanthropic habitats. I have encountered it in Winkler samples from Finca La Pacifica (riparian forest in seasonally dry region), and La Selva Biological Station (lowland rainforest).

Florida (USA)
Deyrup, Davis & Cover (2000) - In Florida this species is found in both moist and dry woods, as well as shaded yards and gardens. Nests are in leaf litter, or in hollow twigs or nuts in the litter. The species Strumigenys eggersi and Strumigenys emmae are the only dacetine ants that are commonly found in dry and mesic habitats of south and central Florida. There is little evidence that native dacetines were ever common in these areas, but if these two exotics continue their northward expansion we may be able to get some idea of their effect on native ants, since we have records of hundreds of litter samples from north Florida. These species are probably more or less specialized predators on entomobryiid Collembola. If they have not had an impact by reducing or replacing the populations of native predators of Collembola in south Florida, they must be a novel predator of the Collembola themselves in this area.

Nomenclature

 *  eggersi. Strumigenys eggersi Emery, 1890b: 69, pl. 7, fig. 9 (w.q.) ANTILLES. Combination in S. (Pyramica): Brown, 1948e: 110; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 119. See also: Brown, 1960b: 46; Bolton, 2000: 184.

Worker
Bolton (2000) - TL 1.6 - 2.0, HL 0.40 - 0.45, HW 0.32 - 0.37, CI 81 - 86, ML 0.23 - 0.28, MI 58 - 65, SL 0.20 - 0.24, SI 58 - 64, PW 0.20 - 0.23, AL 0.40 - 0.46 (20 measured). Characters of Strumigenys gundlachi group; see also notes under Strumigenys gundlachi. Inner margin of mandible feebly convex, with 4 - 8 preapical small denticles on the distal one-third to one-half of the length. Dorsum of pronotum with a single pair of erect hairs (as well as the humeral pair), located on anterior half, usually between the humeral pair. Pair of mesonotal erect hairs short and stiff. On postpetiole ventral spongiform appendage vestigial to absent; lateral lobe absent or at most represented by a narrow marginal non-spongiform carina. First gastral tergite strongly reticulate to reticulate-punctate basally; this sculpture may cover the entire sclerite or tend to diminish in intensity posteriorly.

Type Material
Bolton (2000) - Syntype workers and queens, ANTILLES IS: St Thomas I. (Eggers) [examined].