Pseudomyrmex nigropilosus

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Pseudomyrmex nigropilosus
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Pseudomyrmecinae
Genus: Pseudomyrmex
Species: P. nigropilosus
Binomial name
Pseudomyrmex nigropilosus
(Emery, 1890)

Pseudomyrmex nigropilosus casent0005846 profile 1.jpg

Pseudomyrmex nigropilosus casent0005846 dorsal 1.jpg

Specimen labels


Ward (1993) - Among the Pseudomyrmex species recorded from swollen-thorn acacias, P. nigropilosus is easily identified by its elongate eyes and head (REL 0.55-0.59, CI 0.84-0.90), short petiole (PU 0.69-0.77), and conspicuous black pilosity.


Western Mexico to Costa Rica.

Distribution based on Regional Taxon Lists

Neotropical Region: Costa Rica (type locality), Mexico.

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb


Ward (1993) - Restricted to nesting in swollen-thorn acacias (including Acacia collinsii, A. cornigera and A. hindsii). It is a member of the P. gracilis group and therefore not closely related to the principal group of acacia-ants (P. ferrugineus group). Janzen (1975) points out that P. nigropilosus is essentially a parasite of the Pseudomyrmex/Acacia mutualism. It occupies abandoned or otherwise uninhabited plants and reaps the benefits of this association without protecting the acacia from herbivores or competing plants.



The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • nigropilosus. Pseudomyrma nigropilosa Emery, 1890b: 62, pl. 5, fig. 24 (w.) COSTA RICA. [Also described as new by Emery, 1894k: 51.] Combination in Pseudomyrmex: Kempf, 1958f: 453. See also: Ward, 1993: 159.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.


Ward (1993) - With the traits of the P. gracilis group (see couplet 6 of key) and the following more specific features. Head longer than broad (CI 0.84-0.90); anterior margin of median clypeal lobe convex, conspicuously protruding; dorsolateral margination of pronotum usually blunt; mesonotum more steeply inclined than basal face of propodeum; petiole relatively robust (PU 0.69- 0.77) with a short anterior peduncle; head and mesosoma densely punctulate to coriarious-imbricate, and subopaque; standing pilosity conspicuous on most of the body including the outer faces of the tibiae, consisting largely of black hairs, those on the petiole and Propodeum long (> 0.20 mm) and curved. Color varying from concolorous orange-brown to bicolored orange and black to (western Mexico) predominantly black with orange mottling on the head, mesosoma, and appendages.

Type Material

Ward (1993) - Syntype workers, Liberia, Costa Rica (A. Alfaro) (Museo Civico di Storia Naturale, Genoa, Musee d'Histoire Naturelle Genève) [Examined].


  • Emery, C. 1890b. Voyage de M. E. Simon au Venezuela (Décembre 1887 - Avril 1888). Formicides. Ann. Soc. Entomol. Fr. (6)(10): 55-76 (page 62, pl. 5, fig. 24 worker described)
  • Emery, C. 1894l. Estudios sobre las hormigas de Costa Rica. An. Mus. Nac. Costa Rica 1888- 1889: 45-64 (page 51, also described as new)
  • Kempf, W. W. 1958f. Estudos sôbre Pseudomyrmex. II. (Hymenoptera: Formicidae). Stud. Entomol. (n.s.) 1: 433-462 (page 453, Combination in Pseudomyrmex)
  • Ward, P. S. 1993. Systematic studies on Pseudomyrmex acacia-ants (Hymenoptera: Formicidae: Pseudomyrmecinae). J. Hym. Res. 2: 117-168 (page 159, see also)