Strumigenys emmae

This species has spread throughout tropical and subtropical regions of the world. Longino (Ants of Costa Rica) - "This species has a distribution and habitat preference typical of tropical tramp species (Brown 1954). It occurs widely in many tropical and subtropical regions of the world, including oceanic islands such as Hawaii, and it is found most often in highly disturbed habitats such as beach margins and agricultural areas. The geographic origin of emmae is apparently Australia, where several related species occur (Bolton 2000)."

Identification
Bolton (2000) - Within the Strumigenys emmae-group, emmae is recognised by its combination of short mandibles, broad head, short 4-merous antennae with distinctly angular leading edge on the scape, presence of orbicular hairs on the promesonotum as well as on the cephalic dorsum, absence of erect hairs on the occipital margin and lack of a strong second preapical tooth located between the apicodorsal tooth and the long spiniform preapical tooth.

Distribution
Bolton (2000) - This very successful pantropical tramp species was described and discussed by Brown (1949a) and Bolton (1983). Previous distribution records include Hawaii, Guam, U.S.A., Puerto Rico, West Indies, Cuba, Bahamas, Surinam, Ghana, Equatorial Guinea, India, West Malaysia, Sumatra, Singapore, Philippines, Sulawesi, New Guinea, Solomon Islands, Australia, Vanuatu, Samoa (Brown, 1949a; Wilson & Taylor, 1 967; Kempf, 1972; Taylor, 1976; Bolton, 1983; Deyrup, 1997). A recent survey of Florida by Deyrup & Deyrup (1999) and Deyrup, Davis & Cover (2000) shows that emmae is widely distributed in the state.

Distribution based on Regional Taxon Lists
Afrotropical Region: Comoros, Equatorial Guinea, Ghana, United Republic of Tanzania, Yemen. Australasian Region: Australia, New Caledonia. Indo-Australian Region: Borneo, Guam, Hawaii, Indonesia, Malaysia, Marshall Islands, Micronesia (Federated States of), New Guinea, Northern Mariana Islands, Philippines, Samoa, Solomon Islands, Tonga, Vanuatu. Malagasy Region: Madagascar, Mayotte, Réunion, Seychelles. Nearctic Region: United States. Neotropical Region: Anguilla, Aruba, Barbados, Belize, British Virgin Islands, Cayman Islands, Colombia, Costa Rica, Cuba, Dominican Republic, Ecuador, Galapagos Islands, Greater Antilles, Grenada, Guadeloupe, Mexico, Netherlands Antilles, Puerto Rico, Saint Lucia, Suriname. Oriental Region: India, Sri Lanka, Vietnam. Palaearctic Region: China, Japan.



Biology
This species occurs in both dry and mesic woods, and in disturbed areas such as gardens (Deyrup, Davis & Cover, 2000), and is often found in relatively dry leaf litter. Dealate queens are notable common in leaf litter with small groups of workers, giving the impression that the colonies are producing new queens while the colony is small. This impression, if correct, would fit the strategy of a weedy inhabitant of frequently disturbed sites (Deyrup 1997).

Deyrup and Deyrup (1999) - Two colonies were examined. One was in a hollow acorn in leaf litter in a mesic forest at Spruce Creek Preserve, Volusia Co.; this nest had one queen, 14 workers, and brood. A second colony was found in a hollow, buried acorn of Quercus chapmanii in xeric scrub forest at the Archbold Biological Station. Highlands Co. This colony had one queen, 42 workers, and brood. When the acorn from Highlands Co. was opened, there was one dead, white mite with one leg detached, and a shriveled entombryid collembolan that was being eaten by a larva. This colony was offered sifted leaf-litter and the next day there were 7 dead entomobryids in the colony inside the acorn, including one collembolan that was being eaten by a larva. The next day two larvae were seen feeding on entomobryids. It appears that entomobryid Collembola are a preferred prey of S. emmae.

Deyrup, Davis & Cover (2000) - 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.

Brown (1949) - Nothing is known of the food preferences. Many of the collecting records are of single females taken under objects lying on sea beaches; workers have been taken with the sieve and Berlese funnel in both forested and agricultural areas, usually near the sea. This ant seems to show tolerance for a wider range of environmental conditions than most dacetines.

Tang et al. (2019) - In Hong Kong, this introduced species is found mostly in disturbed habitats, including managed grasslands, isolated patches of urban trees, and with a single record from a secondary forest but located slightly over 100 m from urban habitations. Common in the Mai Po Nature Reserve, a heavily disturbed landscape managed for bird populations. Known elevation range in Hong Kong is from 1 to 407 m. A single alate gyne was collected between June 27 and July 11 in a Malaise trap located within a mangrove area.

Nomenclature

 *  emmae. Epitritus emmae Emery, 1890b: 70, pl. 8, fig. 6 (w.) ANTILLES. Wheeler, W.M. 1908a: 149 (q.). Combination in Quadristruma: Brown, 1949b: 48; in Strumigenys: Bolton, 1999: 1674. Senior synonym of clypeatus, malesiana, wheeleri: Brown, 1949b: 48. See also: Bolton, 1983: 400; Bolton, 2000: 950.
 * clypeatus. Epitritus clypeatus Szabó, 1909: 27, fig. 1 (w.) NEW GUINEA. Junior synonym of emmae: Brown, 1949b: 48.
 * malesiana. Epitritus clypeatus var. malesiana Forel, 1913k: 83 (w.q.) INDONESIA (Sumatra). Junior synonym of emmae: Brown, 1949b: 48.
 * wheeleri. Epitritus wheeleri Donisthorpe, 1916a: 121 (w.) HAWAII. Junior synonym of emmae: Brown, 1949b: 48.

Worker
Bolton (2000) - TL 1.5 - 1.9, HL 0.40 - 0.46, HW 0.33 - 0.39, CI 80 - 88, ML 0.11 - 0.16, MI 26 - 35, SL 0.18 - 0.24, SI 56 - 62, PW 0.21 - 0.25, AL 0.40 - 0.48 (33 measured). Exposed length of fully closed mandible less than width of anterior clypeal margin. Preapical dentition of mandible somewhat variable: inner margin between the spiniform preapical tooth and the apicodorsal tooth may be unarmed, may have a low blunt tubercle or welt, or may have a tiny denticle (intermediates between these are known). Intercalary and preapical dentition may be obscured by the principal teeth when the mandibles are fully closed. Antenna with 4 segments; second funicular segment not obviously much longer than broad. Cephalic dorsum with orbicular hairs; upper scrobe margin fringed with similar hairs and with a clavate apicoscrobal hair. Occipital margin of head without short erect hairs. Leading edge of scape flattened and expanded into an obtuse angle or broad but shallowly convex lobe in the median third of its length. Pronotal humeral hair stiff, stout. Ground-pilosity of pronotal dorsum orbicular but the hairs tending to be smaller than on head. Mesonotum usually with a single pair of short erect hairs but these sometimes absent. Promesonotal dorsum reticulate-punctate, without longitudinal striae. Disc of postpetiole usually with weak sculpture at least in part, only rarely entirely smooth; sides of disc in dorsal view with projecting spongiform tissue. First gastral tergite with short suberect to erect stubbly hairs that are simple to feeble expanded apically. Basigastral costulae at least equal in length to postpetiole disc.

Type Material
Bolton (2000):

Holotype worker, ST THOMAS I. (Antilles).

Epitritus clypeatus Szabó, 1909: 1, figs. la, c. Syntype workers, NEW GUINEA: Berlinhafen (L. Biró); and SINGAPORE (L. Biró) [not seen].

Epitritus clypeatus var. malesiana Forel, 1913e: 83. Syntype workers and queen, INDONESIA: Sumatra (Buttel-Reepen) [not seen].

Epitritus wheeleri Donisthorpe, 1916: 121. Holotype worker, HAWAII: Oahu, Honolulu (R.C.L. Perkins) [not in, holotype lost].

Etymology
Named after Emma Forel, the wife of ant taxonomist Auguste Forel.