Formica difficilis

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Formica difficilis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Formicini
Genus: Formica
Species group: microgyna
Species: F. difficilis
Binomial name
Formica difficilis
Emery, 1893



Specimen Label


Formica difficilis is an ecologically conservative grassland ant species of eastern USA, which once was common in prairies and natural meadows, but now is rare and very sporadic due to nearly total destruction or degradation of suitable habitat. It is a member of the F. microgyna group and is generally found in areas where there are large populations of its temporary host, Formica incerta. It is one of the more heat-tolorant species within the microgyna species group.

At a Glance • Temporary parasite  

Photo Gallery

  • Formica difficilis tending aphids on an oak sapling, eastern Missouri USA. Photo by James Trager.
  • Formica difficilis workers within their nest in 35-year-old reconstructed prairie vegetation in eastern Missouri. Photo by James Trager.


Posterior margin of head and pronotum with sparse short, spatulate or distally flattened and broadened hairs and head slightly shinier than mesosoma.

The scape of workers of this species are without erect or suberect hairs (except at the apex). The tibiae lack erect hairs, except for a row of bristles along the flexor surface. The pronotum and mesonotum have several, erect, blunt-tipped hairs, the propodeum may lack hairs or may have a few. The petiole always has at least a few hairs on the apex and on the sides, the gaster has several scattered hairs.

The queens are tiny, yellow specimens, slightly smaller than the largest workers. The scapes are without erect hairs, the tibiae are without erect hairs except for a row of bristles on the flexor surface. The dorsum of the head has a number of erect hairs, the ventral surface has few erect hairs the dorsum of mesosoma has numerous erect hairs as does the petiole and the gaster. Most hairs are sharp-tipped, except for a few on the mesosoma that have blunt tips.

This species could be confused with Formica querquetulana, but differs in that the head is slightly more shiny than the mesosoma, and their are at least a few hairs present on the posterior lateral corner of the head. It is difficult to separate this species from Formica indianensis, and Formica postoculata, both of which may be synonyms. It can usually be separated on the basis of several erect hairs on the apex of the petiole, which are missing in the other two species. It differs from F. indianensis as there are a number of erect hairs on the dorsum of the head, which are reduced in number in F. indianensis (to 6 of fewer).

Keys including this Species


Eastern United States, roughly co-extensive with its usual temporary host (during colony foundation), Formica incerta.

Latitudinal Distribution Pattern

Latitudinal Range: 47.705° to 35.450576°.

Tropical South

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

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.

Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.


This species occurs in native loamy or sandy grasslands, old fields, lightly grazed pasture and barrens. It avidly tends aphids and membracids and visits extrafloral nectaries on prairie plants, as well as preying on (mostly) small, soft-bodied invertebrates. It is attracted to both sweet and meat baits.

New colonies are established when the small F. difficilis queen invades an existing colony of Formica incerta (whose workers they somewhat resemble), or when it re-entering an established colony of its own species followed by colony fission.

It is a host for the slave-maker Formica pergandei.

Association with Other Organisms

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  • This species is a prey for the Microdon fly Microdon tristis (a predator) (Quevillon, 2018).



Images from AntWeb

Formica difficilis casent0102161 head 1.jpgFormica difficilis casent0102161 profile 1.jpgFormica difficilis casent0102161 dorsal 1.jpgFormica difficilis casent0102161 label 1.jpg
Worker. Specimen code casent0102161. Photographer April Nobile, uploaded by California Academy of Sciences. Owned by MSNG, Genoa, Italy.




The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • difficilis. Formica rufa subsp. difficilis Emery, 1893i: 651, pl. 22, figs. 9, 14 (w.q.m.) U.S.A.
    • Wheeler, G.C. & Wheeler, J. 1953c: 164 (l.).
    • Status as species: Wheeler, W.M. 1904e: 305; Wheeler, W.M. 1904f: 348; Wheeler, W.M. 1906b: 16; Wheeler, W.M. 1913f: 477 (redescription); Cole, 1943a: 389; Creighton, 1950a: 500; Smith, D.R. 1979: 1462; Bolton, 1995b: 194; Coovert, 2005: 152; Ellison, et al. 2012: 151.
    • Senior synonym of consocians, habrogyna: Cole, 1943a: 389.
  • consocians. Formica difficilis var. consocians Wheeler, W.M. 1904f: 371 (w.q.m.) U.S.A.
    • Subspecies of difficilis: Wheeler, W.M. 1906b: 16; Wheeler, W.M. 1913f: 479 (redescription); Wheeler, W.M. 1916m: 597.
    • Junior synonym of difficilis: Cole, 1943a: 389.
  • habrogyna. Formica habrogyna Cole, 1939: 413, figs. A-D (w.q.) U.S.A.
    • Junior synonym of difficilis: Cole, 1943a: 389.



References based on Global Ant Biodiversity Informatics

  • Cole A. C. 1940. A Guide to the Ants of the Great Smoky Mountains National Park, Tennessee. American Midland Naturalist 24(1): 1-88.
  • Cole A. C., Jr. 1943. Synonyms of Formica difficilis Emery (Hymenoptera: Formicidae). Annals of the Entomological Society of America 35: 389.
  • Davis W. T., and J. Bequaert. 1922. An annoted list of the ants of Staten Island and Long Island, N. Y. Bulletin of the Brooklyn Entomological Society 17(1): 1-25.
  • Ellison A. M. 2012. The Ants of Nantucket: Unexpectedly High Biodiversity in an Anthropogenic Landscape. Northeastern Naturalist 19(1): 43-66.
  • Guénard B., K. A. Mccaffrey, A. Lucky, and R. R. Dunn. 2012. Ants of North Carolina: an updated list (Hymenoptera: Formicidae). Zootaxa 3552: 1-36.
  • Ivanov, K. 2019. The ants of Ohio (Hymenoptera, Formicidae): an updated checklist. Journal of Hymenoptera Research 70: 65–87.
  • Ivanov K., L. Hightower, S. T. Dash, and J. B. Keiper. 2019. 150 years in the making: first comprehensive list of the ants (Hymenoptera: Formicidae) of Virginia, USA. Zootaxa 4554 (2): 532–560.
  • Longino, J.T. 2010. Personal Communication. Longino Collection Database
  • Lynch J. F. 1988. An annotated checklist and key to the species of ants (Hymenoptera: Formicidae) of the Chesapeake Bay region. The Maryland Naturalist 31: 61-106
  • MacGown, J.A. and JV.G. Hill. Ants of the Great Smoky Mountains National Park (Tennessee and North Carolina).
  • Smith M. R. 1962. A new species of exotic Ponera from North Carolina (Hymenoptera, Formicidae). Acta Hymenopterologica 1: 377-382.
  • Sturtevant A. H. 1931. Ants collected on Cape Cod, Massachusetts. Psyche (Cambridge) 38: 73-79
  • Van Pelt A., and J. B. Gentry. 1985. The ants (Hymenoptera: Formicidae) of the Savannah River Plant, South Carolina. Dept. Energy, Savannah River Ecology Lab., Aiken, SC., Report SRO-NERP-14, 56 p.
  • Wesson L. G., and R. G. Wesson. 1940. A collection of ants from southcentral Ohio. American Midland Naturalist 24: 89-103.
  • Wheeler W. M. 1904. A new type of social parasitism among ants. Bulletin of the American Museum of Natural History. 20: 347-375.
  • Wheeler W. M. 1904. The ants of North Carolina. Bulletin of the American Museum of Natural History. 20: 299-306.
  • Wheeler W. M. 1906. On the founding of colonies by queen ants, with special reference to the parasitic and slave-making species. Bulletin of the American Museum of Natural History 22: 33-105.
  • Wheeler W. M. 1913. A revision of the ants of the genus Formica (Linné) Mayr. Bulletin of the Museum of Comparative Zoology 53: 379-565.
  • Wheeler W. M. 1928. Ants of Nantucket Island, Mass. Psyche (Cambridge) 35: 10-11.
  • Wheeler, William Morton. 1928. Ants of Nantucket Island, Mass. Psyche. 35(1):10-11.