Formica pallidefulva

Identification
A member of the Formica pallidefulva group.

Most, if not all records of pallidefulva within the northern part of its range, where the color form “nitidiventris” occurs, are Formica biophilica (usually) or occasionally, lighter color morphs of Formica incerta. The short, sparse, gastral pubescence, lack or sparseness of pilosity on the mesosomal dorsum, and the short, straight and flattened gastral pilosity of F. pallidefulva are distinctive for this species in any of its color variants. The difference in SI strongly discriminates this species from F. incerta. The setal characteristics, the shininess and “globose” gaster of this species were expressly mentioned by Latreille (1802) in his original Latin description. Among the species in the group, F. pallidefulva is the only one to frequently lack detectable macrochaetae on the pronotum (34 of 57 specimens) and propodeum (33 of 57 specimens). When mesosomal dorsal pilosity is present in F. pallidefulva, the macrochaetae average shorter than in other species and are usually most numerous on the mesonotum rather than on the pronotum or on the propodeum. Bright-colored southern F. pallidefulva may be distinguished from less pilose nanitic and small workers of F. biophilica by the nearly perfectly rounded propodeum and straight, flattened gastral macrochaetae of F. pallidefulva (versus often faintly right-angular propodeum and narrowly curviconical gastral macrochaetae in F. biophilica). (Trager et al. 2007)

Distribution
Abundant and certainly the most widely distributed species of the group, F. pallidefulva occurs farther north, west and south than others in the group, except that Formica archboldi perhaps extends farther south in Florida. F. pallidefulva occurs throughout the eastern United States and southeastern Canada, then west across the US Great Plains to the lower-elevation Rocky Mountains from Wyoming to New Mexico. F. pallidefulva also has considerable habitat latitude. This ant lives in a variety of native and anthropogenic plant communities and soil types, including dry-mesic to mesic grasslands, woodlands and forests, thickets, lawns, campuses and parks. It is most abundant in mesic, wooded or partially wooded areas, from city parks to closed-canopy forests. In the lower rainfall areas of the Great Plains, it is uncommon and probably restricted to riparian woodlands (Milford, 1999). In the Rocky Mountains, it occurs at lower elevations in meadows, mixed mesophytic forests and in parks and suburbs. F. pallidefulva does not occur in bogs, wet meadows or fens, where it is replaced, in the South by F. biophilica and in the North by Formica montana, Formica glacialis Wheeler, and others. (Trager et al. 2007)

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

Biology
Trager et al. (2007) - Nests of F. pallidefulva may be located in bare soil of grassland and forest footpaths, beneath leaf litter, under small diameter (<10 cm) fallen tree limbs, or under bark of a decomposing stump. Less often the nest occupies a larger, punky, rotten log, especially during late spring when the sexual brood is being reared. F. pallidefulva is the only species in this group which normally inhabits closed-canopy mesic forests and which commonly nests in rotting wood. In non-wooded settings F. pallidefulva may build a small mound nestled in or beside a grass clump.

In the northern and Rocky Mountain parts of its range, at least, the dark brown form of F. pallidefulva is the host to the slavemaker Polyergus lucidus montivagus Wheeler. We have seen F. pallidefulva with this slavemaker in colonies from New York (Long Island), New Jersey, southern Ontario, central Illinois, northern Missouri and Rocky Mountain foothill locales in Colorado and New Mexico. We have seen specimens that look like this Polyergus in the South (northern Mississippi) and we suspect it uses the reddish, southern form of F. pallidefulva there, but have not yet been able to confirm this with a nest collection. Formica creightoni raids this ant in northern Missouri oak woodlands, where its usual Formica neogagates group hosts are lacking. F. pallidefulva is the most frequent of the many hosts of Formica pergandei in Midwest woodlands and savannas.

In the lawns and gardens of the St. Louis MO area, F. pallidefulva is among the native ants most sensitive to subterranean invasion and extermination by the introduced and rapidly spreading invasive ant Tetramorium tsushimae (Steiner et al., in press). However, throughout much of the Southeast, F. pallidefulva often manages to coexist with low-density Solenopsis invicta Buren, Solenopsis richteri Forel, and Solenopsis richteri X invicta populations.

Occasionally, workers and sexuals become covered with a mite (Oplitis sp.?) that reduces their energy level and may cause the demise of the colony. In eastern Missouri, F. pallidefulva colonies are commonly raided by the slavemaker/ant-predator F. rubicunda Emery, which uses F. pallidefulva as prey only (Formica rubicunda “enslaves” only Formica subsericea). When nesting in rotting wood, F. pallidefulva colonies may sometimes be pillaged by pileated woodpeckers. F. pallidefulva often gathers honeydew beneath homopteran-infested plants or from their leaf surfaces, but they have not often been observed to gather honeydew directly from the homopterans. Furthermore, F. pallidefulva makes little effort to defend homopterans, in contrast to F. incerta and Formica archboldi, which often tend and defend them.

Sexuals are present in the nests as early as April in Florida, but not until July in New England and Canada. Males were observed to gather around the nest entrance around sunset in Florida, and males are often lured to lights (but winged females are not) throughout the range. In Missouri, J. Trager observed males, followed by females, flying from the nest, one by one, shortly after sunrise. Despite rather frequent capture of males at lights after dusk, the actual mating flight period is in the morning. In eastern Missouri, J. Trager has over the years caught numerous recently mated females walking about in late morning or early afternoon. Dates of these captures occur from 26 June into early July.

Unlike in other species of this group, worker pupae most often lack cocoons in F. pallidefulva. Wheeler (1904) first noted this contrast between F. pallidefulva and F. incerta in Connecticut, and it was also later noted by Talbot (1948) in Michigan. This difference holds true in numerous colonies of the two species sampled in Missouri by J. Trager. In some colonies of F. pallidefulva, male pupae may also lack cocoons, but queen pupae nearly always are enclosed in cocoons.

Nomenclature

 *  pallidefulva. Formica pallidefulva Latreille, 1802c: 174 (w.) U.S.A. Mayr, 1866b: 889 (q.); Emery, 1893i: 657 (m.). Combination in F. (Neoformica): Wheeler, W.M. 1913a: 82. Senior synonym of succinea: Creighton, 1950a: 550; of nitidiventris, schaufussi: Trager, MacGown & Trager, 2007: 624. See also: Wheeler, W.M. 1913f: 548.
 * schaufussi. Formica schaufussi Mayr, 1866a: 493, fig. 6 (w.) U.S.A. Mayr, 1886d: 427 (q.m.). Combination in F. (Neoformica): Wheeler, W.M. 1913f: 552. Subspecies of pallidefulva: Emery, 1893i: 654; Wheeler, W.M. 1908g: 408. Revived status as species: Creighton, 1950a: 551. Junior synonym of pallidefulva: Trager, MacGown & Trager, 2007: 625.
 * nitidiventris. Formica pallidefulva subsp. nitidiventris Emery, 1893i: 656, pl. 22, figs. 13, 19 (w.q.m.) U.S.A. Wheeler, G.C. & Wheeler, J. 1953c: 159 (l.). Combination in F. (Neoformica): Wheeler, W.M. 1913f: 555. Raised to species: Francoeur, 1977b: 208. Senior synonym of delicata, fuscata, incerta: Creighton, 1950a: 551. Junior synonym of pallidefulva: Trager, MacGown & Trager, 2007: 625.
 * succinea. Formica pallidefulva var. succinea Wheeler, W.M. 1904f: 369 (diagnosis in key) (w.) U.S.A. Wheeler, W.M. 1913f: 551 (q.m.). Junior synonym of pallidefulva: Creighton, 1950a: 550.
 * delicata. Formica pallidefulva subsp. delicata Cole, 1938c: 369 (w.q.) U.S.A. Junior synonym of nitidiventris: Creighton, 1950a: 551.

Worker
Trager et al. (2007) - Includes conventional reddish or brownish yellow F. pallidefulva, as well as darker populations known as F. p. nitidiventris and its synonyms F. p. fuscata and F. p. delicata. This is the shiniest Formica of this group (though smaller workers of Formica biophilica and some series of Formica incerta are also quite shiny). The mesosoma often lacks either appressed pubescence or erect pilosity, or has relatively few, short, erect macrochaetae (Figure 4a). Pubescence, even on gaster, short and sparse (Figure 2a). Sculpture faint to nearly smooth, best developed (to the point of slightly weakening the sheen) in the northeastern part of the range, where the form fuscata occurs. The gaster appears more voluminous than in other members of the group, and is quite shiny, as reflected in the name nitidiventris. Color is highly variable, generally uniform dark brown in Canada and New England, the Black Hills and western mountain areas, and concolorous coppery yellow or weakly bicolored (gaster a little browner) in the deep South. Various intermediate conditions occur in a broad band of territory from southern Missouri and northern Arkansas, across the upper South to the foothills of the southern Appalachians in Georgia and the Carolinas, in the Rocky Montain foothills, and occasionally elsewhere. The transition area between typical pallidefulva and typical nitidiventris is a 300-mile wide band straddling the Mason-Dixon Line. In it, one may occasionally find single-queen colonies containing nearly the full range of color variation. The extreme color forms are weakly distinguished morphometrically, with far northern populations having slightly shorter scapes, but the variation is clinal through the zone of transition (mean SI = 143.08 in the South, 140.94 in transition zone, 139.68 in the North).

Queen
Trager et al. (2007) - Color, gastral pubescence and shininess like the workers’, with the usual differences in size. Sculpture very faint; pubescence short and sparse; pilosity sparse; wings, when present, clear to amber. Mesoscutum lacking the three dark spots characteristic of incerta queens, or these weakly distinct.

Male
Trager et al. (2007) - Pubescence sparse; surface more shining than other species; rarely concolorous dark brown (in those colonies with the most uniformly dark workers), most commonly in north and Rocky Mountains with head and gaster black, mesosoma a little lighter to clear yellowish brown; wings clear to amber ranging in the south and Great Plains to uniform, to only the head black or head concolorous with the honey-colored mesosoma and gaster.

Etymology
This name was coined by Latreille from the Latin adjectives “pallidus” plus “fulvus” meaning pale reddish yellow. This neatly describes the southern, lighter colored variants of this species. Northeastern, Midwestern and western mountain populations of this species are predominantly of darker, black-coffee-brown coloration, but even in these locations many individuals and colonies are bicolored and some may have coloring closer to that of southern populations. (Trager et al. 2007)