Formica pacifica

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Formica pacifica
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Formicini
Genus: Formica
Species: F. pacifica
Binomial name
Formica pacifica
Francoeur, 1973

Formica pacifica casent0005372 profile 1.jpg

Formica pacifica casent0005372 dorsal 1.jpg

Specimen labels

Formica pacifica is a brightly coloured, aggressive species of Formica occupying the west coast of the United States and Canada. This species is a host for the temporary social parasite Formica obscuripes, and potentially more temporarily parasitic and slave raiding Formica species (J. Roth, pers. comm., 2019).


Keys including this Species


Distribution based on Regional Taxon Lists

Nearctic Region: United States (type locality).

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb



Alate brood is produced after hibernation, and, in British Columbia, nuptial flights occur from July to the middle of September (on particularly warm days). Male sexuals are released first, in the early afternoon. Female alates fly soon after. Dealate queens often overwinter before laying their first eggs.

Nesting Habits

Unlike most species from the F. fusca group, Formica pacifica colonies prefer their nests moderately dry. Pupae are stored at the top of the nest, often underneath a rock or another solid surface. Larvae and eggs are usually stored deeper underground, in the additionally moistened parts of the nest.


Formica pacifica collects honeydew. These ants are also scavengers, primarily collecting dead arthropods. Dead, dried out worms are collected in particularly high numbers. Foraging activity primarily occurs in the daytime, with the peak amount of workers dispatched in the afternoon. These ants generally forage alone, but will form trails to plants containing aphids. Once food is found, workers will often recruit others to help feed, or pull food back to the nest.

Association with Other Organisms

This species is a host for the temporary parasite Formica obscuripes in British Columbia, Canada (J. Roth, pers. comm., 2019) and is enslaved by Polyergus mexicanus.



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

  • pacifica. Formica pacifica Francoeur, 1973: 131, figs. 190-197 (w.q.) U.S.A.

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


Francoeur 1973. Figures 190-197.


  • Bolton, B. 1995b. A new general catalogue of the ants of the world. Cambridge, Mass.: Harvard University Press, 504 pp. (page 200, catalogue)
  • Francoeur, A. 1973. Révision taxonomique des espèces néarctiques du groupe fusca, genre Formica (Formicidae, Hymenoptera). Mém. Soc. Entomol. Qué. 3: 1-316 (page 131, figs. 190-197 worker, queen described)