Formica incerta

Strongly favors open habitats such as natural grasslands and pastures.

Identification
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)

Key to US Formica pallidefulva group species

Distribution
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)

Distribution based on Regional Taxon Lists
Nearctic Region: United States.



Biology
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).

Nest Associates
Microdon ocellaris is a primitive syrphid fly that as a larva is a specific predator on ant brood of Formica incerta.

Nomenclature

 *  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.

Worker
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.

Queen
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.

Male
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 [Examined. Five workers on three pins labeled paratypes by A. Francoeur]

Etymology
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)