Strumigenys nigrescens

Inhabits dry coastal forest, an unusual affinity for a Dacetine. Strumigenys nigrescens can also be found in many other habitats as well and its broad ecological tolerances are surely one reason this Strumigenys is relatively well collected from areas within its range.

Identification
Bolton (2000) - The unique dentition (see description below) is immediately diagnostic of nigrescens within the alberti-group., and will immediately separate smaller individuals of this species from Strumigenys furtiva.

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 present; ventral surface of petiole in profile with a deep, conspicuous and very obviously spongiform curtain, its maximum depth at least half that of the peduncle and usually more; disc of postpetiole completely unsculptured and glassy smooth; anterior border of clypeus broadly rounded; basal lamella of mandible immediately followed distally by the tooth-row, without a second lamella that extends forward for half the exposed length of the fully closed mandible; mandibles short, MI 19-24; eye with ten or more ommatidia in total; promesonotal dorsum with a fine median longitudinal carina through most or all of its length; pronotal dorsum partially to mostly sculptured; propodeal dorsum weakly to strongly reticulate-punctate; in full-face view anterior clypeal margin transverse to extremely shallowly convex between points where outer margins of fully closed mandibles intersect the clypeal margin; basal tooth-row of mandible consisting of alternating high narrow acutely triangular teeth and lower bluntly rounded broader teeth; tooth four from base particularly broad and rounded; disc of petiole node in dorsal view much broader than long, roughly transversely rectangular, the sides not converging anteriorly. Similar to Strumigenys fridericimuelleri and Strumigenys parsauga.

Distribution based on Regional Taxon Lists
Neotropical Region: Belize, Costa Rica, Cuba, Dominican Republic, El Salvador, Greater Antilles, Guatemala, Haiti, Honduras, Jamaica, Lesser Antilles, Mexico, Nicaragua, Trinidad and Tobago.

Biology
This species has been found in dry coastal forests and the beach in Costa Rica (Longino, Ants of Costa Rica), and I found a colony in sea grape litter on Long Island, Bahama (Deyrup 1997).

Brown (1953) - A very common ant in Cuba, occurring in all sort of habitats. It is known from one end of the island to the other in agricultural as well as wilder districts. Many of the reported colonies were found nesting under stones. (Brown 1953).

Longino (Ants of Costa Rica) - Occurs in coastal areas, dry forest, and disturbed habitats. My collections are from Winkler samples of sifted leaf litter. Its geographic distribution and habitat preference suggest it could be a tramp species dispersed by commerce.

Nomenclature

 *  nigrescens. Strumigenys alberti var. nigrescens Wheeler, W.M. 1911a: 28 (w.) JAMAICA. Brown, 1953g: 98 (q.); Wheeler, G.C. & Wheeler, J. 1955a: 143 (l.). Combination in S. (Cephaloxys): Emery, 1924d: 325; in Smithistruma: Brown, 1953g: 96; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 125. Raised to species and senior synonym of longipilis, nana: Brown, 1953g: 96. See also: Bolton, 2000: 157.
 * nana. Strumigenys (Cephaloxys) alberti var. nana Santschi, 1930e: 80 (w.) CUBA. Junior synonym of nigrescens: Brown, 1953g: 97.
 * longipilis. Strumigenys (Cephaloxys) alberti subsp. longipilis Weber, 1934a: 50 (w.) CUBA. Combination in Smithistruma: Brown, 1948e: 106. Junior synonym of nigrescens: Brown, 1953g: 97.

Worker
Bolton (2000) - TL 1.8 - 2.0, HL 0.46 - 0.52, HW 0.36 - 0.42, CI 71 - 76, ML 0. 10 - 0.12, MI 21 - 24, SL 0.23 - 0.25, SI 60 - 65, PW 0.22 - 0.26, AL 0.42 - 0.52 (10 measured). Masticatory margin of mandible with characteristic dentition: basal lamella is followed by a small blunt first (basal) tooth; teeth 2, 4, and 6 are low, broad and broadly rounded apically; teeth 3, 5 and 7 are taller and narrower, triangular and acute. No secondary lamella present immediately distal of the basal lamella. Anterior clypeal margin broadly and very shallowly convex between the points where the outer margins of the closed mandibles intersect the clypeal margin, sometimes almost transverse. Apicoscrobal hair flagellate, long and fine, sometimes looped. Eye with 4 - 5 ommatidia in the longest row. Promesonotum with a variably developed median longitudinal carina. At maximum the carina distinct through entire length of pronotum and most of mesonotum; at minimum conspicuous only posteriorly on pronotum and anteriorly on mesonotum. Pronotum dorsally usually completely sculptured with fine costulae, punctation, or both. Occasionally the sculpture weak or even partially effaced anteromedially. Petiole node in dorsal view distinctly broader than long.

Queen
Brown (1953) - TL 2.27, HL 0.5 1, WL 0.58, CI 80, MI 24, forewing Lca. 1 .8 mm. Differs from the worker in the usual ways. Erect feebly spatulate hairs of the head present in the normal Strumigenys pattern, with a pair straddling the ocellar triangle and a transverse row of four on the posterior occiput. Flagelliform hairs as in the worker, similarly placed. Scutum feebly longitudinally rugulose in the center, with a median carinula; scutal hairs subflagellate, curved posteriorly. Color bright ferrugineous; ocellar triangle deeply infuscated.

Type Material
Bolton (2000):

Holotype worker, JAMAICA: Mandeville (A.G. Wight) [examined].

Strumigenys (Cephaloxys) alberti var. nana Santschi, 1930: 80. Holotype worker, CUBA: Havana (A. Bierig) [not seen].

Strumigenys (Cephaloxys) alberti subsp. longipilis Weber, 1934a: 50. Holotype worker, CUBA: Cayamas, 6.3 (E.A. Schwarz). [examined].

References based on Global Ant Biodiversity Informatics

 * Alayo D. P. 1974. Introduccion al estudio de los Himenopteros de Cuba. Superfamilia Formicoidea. Academia de Ciencias de Cuba. Instituto de Zoologia. Serie Biologica no.53: 58 pp. La Habana.
 * Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
 * Branstetter M. G. and L. Sáenz. 2012. Las hormigas (Hymenoptera: Formicidae) de Guatemala. Pp. 221-268 in: Cano E. B. and J. C. Schuster. (eds.) 2012. Biodiversidad de Guatemala. Volumen 2. Guatemala: Universidad del Valle de Guatemala, iv + 328 pp
 * Brown W. L. 1964. The ant genus Smithistruma: a first supplement to the world revision (Hymenoptera: Formicidae). Transactions of the American Entomological Society 89: 183-200.
 * Brown W. L., Jr. 1953. Revisionary studies in the ant tribe Dacetini. Am. Midl. Nat. 50: 1-137.
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
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 * Field Museum Collection, Chicago, Illinois (C. Moreau)
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 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
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 * Longino J. et al. ADMAC project. Accessed on March 24th 2017 at https://sites.google.com/site/admacsite/
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 * Smith, Marion R. 1954. American Museum Novitates. Ants of the Bimini Island Group, Bahamas, British West Indies (Hymenoptera, Formicidae). 1671:1-16
 * Smith, Marion R. 1954. Ants of the Bimini Island Group, Bahamas, British West Indies. American Museum of Natural History. 1671. 1-16.
 * Solomon, S.E. and A.S. Mikheyev. 2005. The ant (Hymenoptera: Formicidae) fauna of Cocos Island, Costa Rica. Florida Entomologist 88(4):415-423
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Weber N. A. 1934. Notes on neotropical ants, including the descriptions of new forms. Revista de Entomologia (Rio de Janeiro) 4: 22-59.
 * Wheeler W. M. 1913. The ants of Cuba. Bulletin of the Museum of Comparative Zoology 54: 477-505.