Formica incerta

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Formica incerta
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Formicini
Genus: Formica
Species: F. incerta
Binomial name
Formica incerta
Buren, 1944



Specimen Label

This species strongly favors open habitats such as natural grasslands and pastures. It is the host of the temporary social parasite Formica difficilis and is enslaved by Formica pergandei and Polyergus lucidus.

Photo Gallery

  • Worker. Photo by Tom Murray.
  • Worker. Photo by Tom Murray.
  • Worker returning to its nest with a caterpillar. Photo by Tom Murray.
  • Workers visiting microscopic nectar glands on the petioles of Maximillian sunflower, Helianthus maximillianii. Photo by James Trager.
  • Worker with brood.
  • Worker returning with prey.
  • These ants can be found in virtually every natural and reconstructed prairie in Missouri, and even in lawns and parks. Shaw Nature Reserve. Photo by James C. Trager
  • Polyergus lucidus returning from a raid to acquire Formica incerta pupae. The browner individuals are F. incerta workers already living in the mixed nest of this socially parasitic ant. July 2010, eastern Missouri, USA. Photo by James Trager.
  • Myrmica worker drags a Formica incerta worker killed by Polyergus mexicanus in a rare, and lethal, raid on a non-host species. Photo by James Trager, taken in Missouri.


A member of the Formica pallidefulva group.

Metrically, F. incerta is distinguished from the other species in the group by a relatively broad head and short scapes. In the Northeast, more pilose F. incerta individuals may be confused with Formica dolosa, and F. incerta specimens with little pilosity may be confused with Formica pallidefulva. The geographic range of F. pallidefulva completely overlaps that of F. incerta, and most places where they are found together in the field, F. incerta appears lighter in color and less shiny than F. pallidefulva, due to some faint tessellation on the mesosoma and somewhat longer, denser pubescence on the gastral dorsum of F. incerta. Mesosomal and gastral pilosity is usually much less abundant than in F. dolosa and averages slightly less abundant than in Formica biophilica. Also, F. incerta is darker and shinier than sympatric F. dolosa. See F. biophilica account for the differences between F. incerta and that species. (Trager et al. 2007)

Keys including this Species


This species occurs from New England and the Great Lakes States west to Minnesota, Nebraska and low elevation grasslands of Colorado (and New Mexico?). It extends south in eastern US to the balds, meadows and old fields of the southern Appalachians. F. incerta is especially abundant in native mesic and dry-mesic grasslands, but also occurs in parks, campuses and lawns. Field and forest clear-cuts. In the Northeast, it occurs in heathland and sand barrens, and in the Midwest it is characteristic and abundant in prairie remnants, botanically diverse old fields and meadows, and native prairie reconstructions. (Trager et al. 2007)

Latitudinal Distribution Pattern

Latitudinal Range: 45.006065° to 35.585°.

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.


Trager et al. (2007) - Nests are in bare soil, or beneath a grass clump, in the latter case often with a small, irregular, conical (5-15 cm wide, 10-20 cm tall) mound of soil and plant fragments. This is often the first Formica species to become abundant on restored native grasslands, “Conservation Reserve Program” grassland plantings on former farmland and cut-over forests. A healthy population of F. incerta may facilitate colonization by its parasites Formica difficilis and Formica pergandei, if these occur nearby. It is less abundant than Formica pallidefulva in lawns, campuses and parks.

This is often the most abundant Formica species in mesic tallgrass prairies from central Illinois, Nebraska and south to Oklahoma and northeast Arkansas, and also in balds, meadows and old fields at higher elevations of the southern Appalachian Mountains. Sweepnet samples from all these types of habitats rarely fail to include F. incerta, and thus insect collections housed at institutions near them may be rife with samples of individuals so captured. In the Great Lakes Region and New England, this species is more associated with sandy soils and pastureland and often nests under rocks. In the northern glaciated prairie region, F. incerta can be a dominant ant in sand prairies, but is largely displaced from sites with moister, finer-textured soils, which are dominated by aggressive, mound-building Formica species.

F. incerta appears to be the only host of Polyergus lucidus lucidus collections examined from New England states, New Jersey, southern Ontario, Wisconsin and Missouri. F. incerta is also frequent among the many hosts of Formica pergandei and in western Missouri prairies commonly occurs as a slave of this species, either alone or in mixed populations with Formica subsericea. F. incerta appears to be the primary host of alloparasitic (dispersing) queens of Formica difficilis Emery, the queen of which bears a superficial resemblance to F. incerta workers. Indeed, Wheeler (1904) first used the term “temporary social parasitism” to describe the relationship he elucidated between F. difficilis (as var. consocians) and F. incerta in Connecticut.

This ant often visits extrafloral nectaries of sunflowers, partridge peas and other prairie plants. It also tends aphids and membracids on a variety of plants. F. incerta workers defend these sugar sources from non-nest mates of their own species, from other, smaller ant species and from some parasitoids. However, in areas where there are greater numbers of aggressive mound-building prairie Formica species (e.g. Formica montana, Formica obscuripes Forel), F. incerta becomes more furtive and opportunistic in its honeydew gathering, as described below for F. pallidefulva. Foraging strategy and recruitment to food sources has been well studied in F. incerta (and incidentally, in F. dolosa) by Robson and Traniello (1998 and included references to their earlier work). These authors identified their study subject as F. schaufussi in the articles, but vouchers sent by Robson were examined for this revision. These were mostly F. incerta, but also included a sample of F. dolosa.

In recently burned grasslands, flickers prey heavily on Formica species, including F. incerta, especially on sunny, late winter days when workers migrate intranidally toward the surface, seeking warmth.

Alates occur in the nests in July and August in New England and the northern prairies, and a few weeks earlier in the unglaciated prairie region and southern Appalachians. It is worth noting that the maturation of alates of F. pallidefulva may precede that of F. incerta in by two or three weeks, suggesting a possible temporal mechanism for reproductive isolation. Flights have not been observed, but several mated queens have been captured walking about in mid to late morning in Missouri. In the lab, these recently mated queens are “nervous” in captivity and often fail to rear their first workers, in contrast to the ready adaptability to captive conditions of F. pallidefulva queens. Worker pupae are typically enclosed in a light tan cocoon and sexual pupae have darker tan cocoons. This is in contrast to the frequently naked worker pupae of F. pallidefulva, as was earlier noted by both Wheeler (1904) and Talbot (1948).

Association with Other Organisms

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  • This species is a mutualist for the aphid Rhopalosiphum nymphaeae (a trophobiont) (Jones, 1927; Saddiqui et al., 2019).


  • This species is a host for the  Microdon ocellaris (a predator) in Maine, Massachusetts, New York, Pennsylvania (type), South Carolina (Curran, 1924).


  • This species is a host for the fungus Laboulbenia formicarum (a parasite) (Quevillon, 2018) (encounter mode primary; direct transmission; transmission within nest).
  • This species is a host for the fungus Laboulbenia formicarum (a pathogen) (Espadaler & Santamaria, 2012).

Flight Period

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec


Life History Traits

  • Queen number: polygynous (Rissing and Pollock, 1988; Frumhoff & Ward, 1992)



Mcz-ent00669877 Formica incerta hef.jpgMcz-ent00669877 Formica incerta hal.jpgMcz-ent00669877 Formica incerta had.jpgMcz-ent00669877 Formica incerta lbs.JPG
Worker. . Owned by Museum of Comparative Zoology.

Images from AntWeb

Formica incerta casent0172883 head 1.jpgFormica incerta casent0172883 profile 1.jpgFormica incerta casent0172883 dorsal 1.jpgFormica incerta casent0172883 label 1.jpg
Worker. Specimen code casent0172883. Photographer April Nobile, uploaded by California Academy of Sciences. Owned by MCZ, Cambridge, MA, USA.
Formica incerta casent0172884 head 1.jpgFormica incerta casent0172884 profile 1.jpgFormica incerta casent0172884 dorsal 1.jpgFormica incerta casent0172884 label 1.jpg
Worker. Specimen code casent0172884. Photographer April Nobile, uploaded by California Academy of Sciences. Owned by MCZ, Cambridge, MA, USA.
Formica incerta casent0172881 head 1.jpgFormica incerta casent0172881 profile 1.jpgFormica incerta casent0172881 dorsal 1.jpgFormica incerta casent0172881 label 1.jpg
Worker. Specimen code casent0172881. Photographer April Nobile, uploaded by California Academy of Sciences. Owned by MCZ, Cambridge, MA, USA.


Images from AntWeb

Formica incerta casent0172885 head 1.jpgFormica incerta casent0172885 profile 1.jpgFormica incerta casent0172885 dorsal 1.jpgFormica incerta casent0172885 label 1.jpg
Queen (alate/dealate). Specimen code casent0172885. Photographer April Nobile, uploaded by California Academy of Sciences. Owned by MCZ, Cambridge, MA, USA.


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

  • incerta. Formica (Neoformica) pallidefulva subsp. incerta Buren, 1944a: 309 (w.q.m.) U.S.A. [First available use of Formica pallidefulva subsp. schaufussi var. incerta Emery, 1893i: 655; unavailable name.] Junior synonym of nitidiventris: Creighton, 1950a: 551. Revived from synonymy and raised to species: Trager, MacGown & Trager, 2007: 621.

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



Trager et al. (2007) - A relatively shiny grassland Formica with a relatively broad head (mean CI = 86.77), sides of head more convex (Figure 3c) and scapes relatively short (mean SI = 132.99). Head and gaster rich, dark brown (northeast) to brownish-yellow with darker tip (prairie region). Mesosoma and legs yellowish-brown to light yellowish-brown. Mesosoma often a little lighter than head, and both lighter than gaster. Specimens in the Great Plains portion of the range are nearly concolorous brownish yellow except for the darker gastral apex. Mesosomal macrochaetae of F. incerta typically often conspicuously shortest on propodeum. Erect pilosity on gaster relatively short, straight or only slightly curved, if curved, usually below the mid-point of the length of the macrochaetae. Gaster shiny, but its sheen dulled by faint tessellation and medium density pubescence (Figure 2c) composed of pale grayish appressed microchaetae.


Trager et al. (2007) - Color, gastral pubescence and shininess like the workers’, with the usual differences in size. Color pattern differing from workers’ and from that of queens of all other species in that there are three distinct, dark spots on the mesoscutum, one anteromedian and two lateral over the parapsidal sulci. These may may cover most of the mesoscutal area or may be reduced to longitudinal dark elliptical marks. Upper portion of head, pronotum, sides of mesothorax, propodeum and gastral dorsum with faint tessellation. Wings, when present, clear brownish to clear smoky gray.


Trager et al. (2007) - Pubescence and pilosity abundant; mesosomal dorsum dull-punctate; entire body uniform black or dull blackish brown, legs reddish brown; wings clear brownish to clear smoky gray. Averages smaller than the nearly similar Formica dolosa and smaller and of more uniform blackish color than males of Formica biophilica.

Type Material

Trager et al. (2007) - Formica (Neoformica) pallidefulva subsp. incerta: Buren, 1944 [First available use of incerta] Syntype workers, District of Columbia, iv-13-1886 (Museo Civico di Storia Naturale, Genoa) [Examined. Five workers on three pins labeled paratypes by A. Francoeur]


This name was coined by Emery from the Latin adjective incertus meaning uncertain. This seems appropriate to describe Emery’s own and subsequent authors’ doubts regarding the validity of this species. (Trager et al. 2007)


References based on Global Ant Biodiversity Informatics

  • Amstutz M. E. 1943. The ants of the Kildeer plain area of Ohio (Hymenoptera, Formicidae). The Ohio Journal of Science 43(4): 165-173.
  • Clark A. T., J. J. Rykken, and B. D. Farrell. 2011. The Effects of Biogeography on Ant Diversity and Activity on the Boston Harbor Islands, Massachusetts, U.S.A. PloS One 6(11): 1-13.
  • 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. 1936. An annotated list of the ants of Idaho (Hymenoptera; Formicidae). Canadian Entomologist 68(2):34-39
  • 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.
  • Del Toro I., K. Towle, D. N. Morrison, and S. L. Pelini. 2013. Community Structure, Ecological and Behavioral Traits of Ants (Hymenoptera: Formicidae) in Massachusetts Open and Forested Habitats. Northeastern Naturalist 20: 1-12.
  • Downing H., and J. Clark. 2018. Ant biodiversity in the Northern Black Hills, South Dakota (Hymenoptera, Formicidae). Journal of the Kansas Entomological Society 91(2): 119-132.
  • Ellison A. M., and E. J. Farnsworth. 2014. Targeted sampling increases knowledge and improves estimates of ant species richness in Rhode Island. Northeastern Naturalist 21(1): NENHC-13–NENHC-24.
  • Emery C. 1893. Beiträge zur Kenntniss der nordamerikanischen Ameisenfauna. Zoologische Jahrbücher. Abteilung für Systematik, Geographie und Biologie der Tiere 7: 633-682.
  • Francoeur A. 2010. Liste des especes de fourmis (Formicides, Hymenopteres). Entomofaune du Quebec. Document Faunique no. 1, Version 5, 0. 1-10 pp.
  • General D. M., and L. C. Thompson. 2011. New Distributional Records of Ants in Arkansas for 2009 and 2010 with Comments on Previous Records. Journal of the Arkansas Academy of Science 65: 166-168.
  • 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.
  • Headley A. E. 1943. The ants of Ashtabula County, Ohio (Hymenoptera, Formicidae). The Ohio Journal of Science 43(1): 22-31.
  • Ivanov K. 2015. Checklist of the ants (Hymenoptera: Formicidae) of Ohio. Conference: Ohio Natural History Conference, At Columbus OH
  • 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.
  • Kittelson P. M., M. P. Priebe, and P. J. Graeve. 2008. Ant Diversity in Two Southern Minnesota Tallgrass Prairie Restoration Sites. Jour. Iowa Acad. Sci. 115(1–4): 28–32.
  • Menke S. B., E. Gaulke, A. Hamel, and N. Vachter. 2015. The effects of restoration age and prescribed burns on grassland ant community structure. Environmental Entomology
  • Menke S. B., and N. Vachter. 2014. A comparison of the effectiveness of pitfall traps and winkler litter samples for characterization of terrestrial ant (Formicidae) communities in temperate savannas. The Great Lakes Entomologist 47(3-4): 149-165.
  • Ouellette G. D. and A. Francoeur. 2012. Formicidae [Hymenoptera] diversity from the Lower Kennebec Valley Region of Maine. Journal of the Acadian Entomological Society 8: 48-51
  • Sturtevant A. H. 1931. Ants collected on Cape Cod, Massachusetts. Psyche (Cambridge) 38: 73-79
  • Tanquary M. C. 1912. A preliminary list of ants from Illinois. Trans. Ill. Acad. Sci. 4: 137-142.
  • Trager J. C., J. A. MacGown, and M. D. Trager. 2007. Revision of the Nearctic endemic Formica pallidefulva group. Memoirs of the American Entomological Institute 80: 610-636
  • Wheeler W. M. 1906. Fauna of New England. 7. List of the Formicidae. Occasional Papers of the Boston Society of Natural History 7: 1-24.
  • 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. 1916. Formicoidea. Formicidae. Pp. 577-601 in: Viereck, H. L. 1916. Guide to the insects of Connecticut. Part III. The Hymenoptera, or wasp-like insects, of Connecticut. Connecticut State Geological and Natural History Survey. Bulletin 22: 1-824.