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Species: Pseudomyrmex gracilis   (Fabricius, 1804) 

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Current Valid Name:

Taxonomic History (provided by Barry Bolton, 2023)

Extant: 1 valid subspecies

Formica gracilis Fabricius, 1804 PDF: 405 (w.) GUYANA. Neotropic. Primary type information: Primary type material: lectotype worker (by designation of Ward, 1989a PDF: 439). Primary type locality: lectotype Guyana: Essequibo (no collector’s name). Primary type depository: ZMUC. Secondary type information: Secondary type material: paralectotype workers (number uncertain). Secondary type locality: same as for lectotype. Secondary type depositories: ZMUC, ZMUK. Type notes: 1) Original locality data: “Habitat in America meridionali. Dom. Smidt. Mus. Dom. Lund”; the Essequibo locality is cited by Ward, 1989a PDF: 439; 2) According to Zimsen, 1964 PDF: 425, there are 3 specimens in ZMUC, and 1 in ZMUK, but Ward, 1989a PDF: 439 (in text), says that one ZMUC specimen is not conspecific with the lectotype. AntCat AntWiki HOL

Taxonomic history

Lectotype designation: Ward, 1989a PDF: 439.
Combination in Leptalea: Erichson, 1839 PDF: 309.
Combination in Pseudomyrma: Roger, 1862c PDF: 289.
Combination in Pseudomyrmex: Kusnezov, 1953f PDF: 214.
Status as species: Erichson, 1839 PDF: 309; Roger, 1862c PDF: 289; Roger, 1863b PDF: 25; Mayr, 1863a PDF: 452; Mayr, 1870a PDF: 408; Smith, 1877b PDF: 60; Emery, 1878a PDF: ix (in list); Emery, 1890b PDF: 65; Cameron, 1891: 95; Dalla Torre, 1893 PDF: 57; Forel, 1895b PDF: 122; Emery, 1896h PDF: 625; Pergande, 1896 PDF: 874; Forel, 1899b PDF: 90; Forel, 1899j: 274; Forel, 1907d PDF: 26; Forel, 1907h PDF: 7; Forel, 1908c PDF: 60; Forel, 1908 PDF: 382; Wheeler, 1908h PDF: 421; Forel, 1909a PDF: 250, 260; Wheeler, 1911a PDF: 22; Forel, 1912h PDF: 19; Bruch, 1914 PDF: 224; Donisthorpe, 1915f PDF: 336; Mann, 1916 PDF: 426; Crawley, 1916b PDF: 369; Wheeler, 1916c PDF: 3; Luederwaldt, 1918 PDF: 46; Wheeler, 1918b PDF: 24; Emery, 1921c PDF: 29; Wheeler, 1922e PDF: 4; Mann, 1922 PDF: 20; Wheeler, 1923a PDF: 3; Wheeler, 1925a PDF: 10; Borgmeier, 1927c PDF: 72; Donisthorpe, 1927c: 387; Menozzi, 1927c PDF: 267; Gallardo, 1932a PDF: 47 (redescription); Menozzi, 1935b PDF: 191; Eidmann, 1936a PDF: 37; Wheeler, 1942 PDF: 166; Enzmann, 1944 PDF: 61; Weber, 1948b PDF: 81; Brown, 1949a PDF: 43; Creighton, 1950a PDF: 80; Kusnezov, 1953c PDF: 337; Kusnezov, 1953f PDF: 214; Kempf, 1961a PDF: 370; Kempf, 1961b PDF: 498; Kempf, 1972b PDF: 219; Kempf & Lenko, 1976 PDF: 63; Zolessi et al., 1988: 5; Ward, 1989a PDF: 439; Brandão, 1991 PDF: 375; Ward, 1992 PDF: 80 (in table); Ward, 1993 PDF: 155 (redescription); Bolton, 1995b: 373; Ward, 1999b PDF: 521 (redescription); Deyrup et al., 2000: 295; Deyrup, 2003 PDF: 46; Ward, 2007b PDF: 40, 55; Branstetter & Sáenz, 2012 PDF: 264; Bezděčková et al., 2015 PDF: 125; Wetterer et al., 2016 PDF: 23; Deyrup, 2017: 41; Ward, 2019 PDF: 1102.
Senior synonym of Pseudomyrmex canescens: Ward, 1993 PDF: 155; Bolton, 1995b: 373.
Senior synonym of Pseudomyrmex dimidiata: Mayr, 1870a PDF: 408; Ward, 1993 PDF: 155; Bolton, 1995b: 373.
Senior synonym of Pseudomyrmex mexicana: Ward, 1993 PDF: 155; Bolton, 1995b: 373.
Senior synonym of Pseudomyrmex pilosula: Ward, 1993 PDF: 155; Bolton, 1995b: 373.
Senior synonym of Pseudomyrmex sericata: Ward, 1993 PDF: 155; Bolton, 1995b: 373.
Senior synonym of Pseudomyrmex volatilis: Ward, 1993 PDF: 155; Bolton, 1995b: 373.
Material of the unavailable name Pseudomyrmex gracilis mexicana guayaquilensis referred here by Ward, 1993 PDF: 156; Bolton, 1995b: 373.
// Distribution


  Geographic regions (According to curated Geolocale/Taxon lists):
    Americas: Argentina, Barbados, Belize, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Honduras, Jamaica, Mexico, Nicaragua, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, United States, Uruguay, Venezuela
    Oceania: Hawaii
  Biogeographic regions (According to curated Bioregion/Taxon lists):
    Nearctic, Neotropical, Oceania
  Native to (according to species list records):
    Nearctic, Neotropical bioregions

Distribution Notes:

Pseudomyrmex gracilis is a widespread New World species, ranging from southern United States to Argentina and Uruguay. It is present as an introduced species in Hawaii and Florida.


Befitting its wide distribution and variable phenotype, P. gracilis can be found in a variety of habitats from mangroves and thorn scrub to rainforest. It is often particularly common in disturbed situations such as old fields, roadsides, and secondary forest. Nests are usually located in dead twigs or small branches, belonging to a great variety of woody plants. In Central America (Mexico to Panama) there are a substantial number of records of colonies occupying swollen-thorn acacias. In a few localities P. gracilis is a common acacia inhabitant and under these circumstances it may exhibit local adaptation and phenotypic differentiation (Ward, 1993).


  • masticatory margin of mandible with 7-10 teeth
  • median clypeal lobe laterally rounded
  • eyes large and elongate (REL2 0.54-0.60)
  • pronotum dorsolaterally submarginate
  • petiole long and slender (PLI 0.46-0.57) with a well developed anterior peduncle
  • head and mesosoma densely and finely punctulate-coriarious to coriarious-imbricate, subopaque to sublucid (not matte) in appearance
  • standing pilosity abundant, fine, predominantly pale silvery-white (not black), common on mesosoma dorsum and on external faces of tibiae
  • size and color extremely variable (HW 1.39-2.07), varying from unicolorous black (appendages lighter) to unicolorous orange-brown, with many intermediate and bicoloured combinations

Taxonomic Notes:

Pseudomyrmex gracilis presents one of the more taxonomically challenging problems in the genus Pseudomyrmex. The concept of P. gracilis adopted here encompasses an impressive amount of phenotypic variability. Collections from single regions often give the impression that this variation is distributed bimodally or multimodally, as more or less discrete morphs. For example, nest samples from Costa Rica can be segregated on the basis of worker morphology into (i) a large (HW > 1.80), usually lighter-colored form (with orange mesosoma, petiole, and postpetiole, and black head and gaster), (ii) a smaller, bicolored, usually more heavily infuscated form, and (iii) an all-black form of variable size. The first two are typically found in open or xeric habitats while the third is more common in closed forest, suggesting some ecotypic differentiation. Yet when large enough sample sizes are obtained all degrees of intermediacy in size and color are encountered, and the variation in color (less so size) can be seen among individuals (workers and alate queens) from the same nest. Thus, if there are ecotypes they do not appear to be reproductively isolated.


(Dutch vernacular name: zwarte acaciamier)


Beardsley, J. W. 1979. Notes on Pseudomyrmex gracilis mexicanus (Roger). Proceedings of the Hawaiian Entomological Society 23: 23.

Ward, P. S. 1985. The Nearctic species of the genus Pseudomyrmex (Hymenoptera: Formicidae). Quaestiones Entomologicae 21: 209-246.

Ward, P. S. 1993. Systematic studies on Pseudomyrmex acacia-ants (Hymenoptera: Formicidae: Pseudomyrmecinae). Journal of Hymenoptera Research 2: 117-168.

Ward, P. S. 1999. Systematics, biogeography and host plant associations of the Pseudomyrmex viduus group (Hymenoptera: Formicidae), Triplaris- and Tachigali-inhabiting ants. Zoological Journal of the Linnean Society 126: 451-540.

Wetterer, J. K. 2010. Worldwide spread of the graceful twig ant, Pseudomyrmex gracilis (Hymenoptera: Formicidae). Florida Entomologist 93: 535-540.

Taxonomic Treatment (provided by Plazi)

Scientific Name Status Publication Pages ModsID GoogleMaps
Pseudomyrmex gracilis   Wild, A. L., 2007, A catalogue of the ants of Paraguay (Hymenoptera: Formicidae)., Zootaxa 1622, pp. 1-55: 40, (download) 40 21367
Pseudomyrmex gracilis   Wild, A. L., 2007, A catalogue of the ants of Paraguay (Hymenoptera: Formicidae)., Zootaxa 1622, pp. 1-55: 55, (download) 55 21367

Specimen Habitat Summary

Found most commonly in these habitats: 62 times found in tropical dry forest, 56 times found in rainforest, 42 times found in rainforest edge, 43 times found in edge of second-growth rainforest, 32 times found in roadside vegetation, 41 times found in montane wet forest, 21 times found in roadside, 26 times found in roadside edge, 26 times found in tropical moist forest, 18 times found in second-growth rainforest, ...

Found most commonly in these microhabitats: 144 times on low vegetation, 75 times ex dead twig, 33 times beating vegetation, 32 times Malaise trap, 10 times ex dead twig of Gliricidia sepium, 10 times on tree trunk, 7 times ex dead twig of vine, 9 times ex dead weed stalk, 13 times strays, 12 times nest in twig above ground, 7 times ex swollen-thorn Acacia, ...

Collected most commonly using these methods: 66 times Malaise, 58 times Fogging, 51 times search, 39 times Beating, 32 times Malaise trap, 34 times canopy fogging, 29 times direct collection, 12 times hand collecting, 12 times sweeping, 9 times blacklight trap, 9 times beating vegetation (1 hour), ...

Elevations: collected from 1 - 2480 meters, 356 meters average

Collect Date Range: collected between 1903-03-02 00:00:00.0 and 2020-01-24 00:00:00.0

Type specimens: Holotype of Pseudomyrma canescens: casent0902843; Holotype of Pseudomyrma sericata: casent0902845; Holotype of Pseudomyrma volatilis: casent0902846; Lectotype of Pseudomyrma pilosula: casent0902844; Lectotype of Pseudomyrma variabilis: casent0902842; syntype of Pseudomyrma gracilis atrinoda: casent0915509; syntype of Pseudomyrma gracilis glabriventris: casent0915507; type of Pseudomyrma bicolor: focol0524; Type of unavailable quadrinomial: Pseudomyrma gracilis mexicana guayaquilensis: casent0907478

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