Key to US Formica pallidefulva group species

The following key is based on [[Media:Trager MacGown Trager 2007.pdf|Trager, MacGown & Trager, 2007]]. See also the description of the Formica pallidefulva group.

1

 * Mesosomal dorsum without erect setae or with a small cluster on the mesonotum and/or a few erect hairs elsewhere; gaster shiny with sparse, short appressed pubescence and relative short, sparse, blunt pilosity (Figures 4a, 6a); color highly variable, ranging from bright tawny or coppery yellow (southern United States) to very dark brown (mountains in northern and western United States) and including many intermediate colorations; mesic habitats, from gardens, parks and prairies to closed-canopy forests, or more shaded parts of drier sites . . . . . Formica pallidefulva


 * Mesosomal dorsum with several to many erect setae on pronotum, mesonotum and propodeum; gastral tergite I shiny to dull with appressed pubescence of medium to high density (Figures 4b-e, 4b-e); the average distance between the individual appressed setae approximately equaling the average length of setae to much less; various open grassland, heath, or barrens and open dry woodland habitats (mesic forests or forest edge in the extreme southern U.S.) . . . . . 2

2
return to couplet #1
 * Mesosomal and gastral integument dulled by fine, but notable sculpture; mesosomal dorsum feebly or (at some viewing angles) not shining; gaster usually with dense pubescence (Figures 4d-e, 6d-e), appressed setae on gastral tergite I separated by about 0.5× (or less) the average setal length (if gastral setae less abundant, then mesosomal and gastral integument dulled by fine sculpture); propodeum usually with visible pubescence . . . . . 3


 * Mesosomal and gastral integument somewhat shining, with fainter sculpture; gaster less densely pubescent (Figures 4b-c, 6b-c); gastral tergite I with appressed setae separated by about 0.5-1.0× their average length; propodeum with sparse pubescence or none . . . . . 4

3
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 * Reddish, often weakly bicolored; mesosoma with visible pubescence and gastral integument dulled or even velvety looking due to dense pubescence; larger workers’ integument appearing matte in dorsal or oblique dorsal view; numerous erect macrochaetae on all dorsal surfaces, those on first tergite usually long, tapering and typically curved (Figure 6e); size generally larger, HL 1.31-2.06, HW 1.05-1.70, and WL 2.12-3.48; eyes proportionally smaller to head size (OI 28.58); widely distributed in eastern United States (rare west of 100th meridian); reddish-brown (northeastern United States) to light reddish (southeastern and midwestern United States) . . . . . Formica dolosa


 * Dark brown to blackish brown; with fine coriaceous sculpture on mesosoma and foveolae on gastral dorsal surface; erect setae shorter and fewer, at least on mesosoma, erect setae often blunt-tipped and without notable curvature, even on gastral tergite I (Figure 6d); size smaller, HL 1.31-1.58, HW 1.03-1.39, and WL 2.08-2.65; eyes proportionally larger (OI 31.26); found in long-leaf pine sandhills and scrub or sand pine woodlands in southeastern United States (Alabama, Florida, and Georgia) . . . . . Formica archboldi

4
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 * Length of the longest macrochaetae of gastral tergite I, 0.15-0.22 mm (Figure 4c, 6c, Table 2); color dingy yellowish or reddish brown with gaster or head and gaster a little to significantly darker (midwestern United States, Great Plains) or more uniformly brown with only the mesosoma a bit more yellow (northeastern United States); overall size averages smaller (HL 1.15-1.64, HW 1.01-1.43, and WL 1.86-2.67); head wider and scapes shorter (See CI and OI, Table 1, also Figures 2 & 3); queen with three distinct dark spots on mesoscutum, one anteromedian and two lateral over parapsidal sulci (spots may be reduced to longitudinal dark elliptical marks) . . . . . Formica incerta


 * Erect setae of first gastral tergite long and curved, longest macrochaetae 0.20 – 0.30 mm (Figure 4b, 6b, Table 2); color bright reddish-yellow or with gaster only slightly darker (Beware: Gaster of this species sometimes stains black in mounted specimens.); mesosomal dorsal integument a little more shining to quite smooth except in largest workers; overall size averages larger (HL 1.37-1.82, HW 1.05-1.56, and WL 2.22-2.93); head more narrow in smaller specimens and scapes longer (See CI and OI, Table 1, also Figures 2 and 3) in smaller specimens (larger workers tend to have wider heads and shorter scapes); queen lacking dark spots on mesoscutum . . . . . Formica biophilica