Stigmatomma pallipes

In California this species has been found in chaparral, riparian woodland, oak woodland and mixed forest (with oak, douglas fir and pine). Isolated workers or nest fragments have been collected in litter samples and under stones. Because of their subterranean habits the workers are infrequently encountered, but males are not uncommon at light in late summer in some foothill localities. Foraging behavior is probably similar to that of S. pallipes workers from eastern United States, which have been reported feeding on centipedes and other soil arthropods. (Ward 1988)

Identification
Worker: inner border of mandible and anterior clypeal margin broadly convex in outline; California specimens smaller in size than those of Stigmatomma oregonense (HW 0.99-1.15), with narrower heads (CI 0.86-0.90).

Stigmatomma pallipes in the eastern United States is not a common ant but it can be discovered by turning over stones and searching carefully through rotten wood on the ground. These small, dark reddish-brown ants are about 1/4 inch in length. The eyes are very small, with only one or two facets. There is a row of small teeth on the anterior margin of the clypeus and the mandibles are long and linear with a row of bi-dentate teeth on the inner margin. The petiole is broadly joined to the gaster.


 * Key to Stigmatomma of the New World
 * Key to Stigmatomma of the United States

Distribution
This species is widely distributed in the United States. It has been reported from most eastern states except Maine and Pennsylvania. It is also known from California and is found sporadically in the mountains of Arizona.

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



Habitat
The small colonies are most common in wooded areas where they are found in rotten logs and under stones. In New England these ants are often found nesting under rock walls.

Abundance
This ant species is seldom if ever abundant. Due to their small colony size and nest location under rocks and in logs in forests, this ant species is difficult to find.

Biology
The workers are slow moving and not regularly encountered. The pupae are covered with a brown silk case that helps in identification in the field. The queen is worker-like and inconspicuous. The males and females mate during the late summer months. Females mate with males on rocks on the ground in forested areas during the first week of September in New England.

Nests are small, often far fewer than 100 workers, and diffuse. In the eastern United States workers have been found collecting centipedes and other soil arthropods. Prey are captured and held in the worker's heavily toothed mandibles, then paralyzed by a powerful sting. The crytpic foragers are not regularly seen above ground as they prefer to search for food in the same places where this species' forms their nests - in the soil, litter and decaying wood. Amblyopone pallipes is a forest dweller throughout most of its range. In California this species has been found in chaparral, riparian woodland, oak woodland and mixed forest (oak, Douglas fir and pine) habitats. Isolated workers or nest fragments have been collected in litter samples and under stones.

Haskins (1924) provides this account of their nesting biology: ....ordinarily found in thick, damp woodlands, the typical localities in which most timid hypogeaic forms find refuge. Although the majority of these forms seem dependent for their continued existence upon these forests, with their concomitant opportunity of escape from more dominant types, it is certain that pallipes has not become entirely so, nor has it completely lost the ability to exist in proximity with glade or even field forms. In Petersham, Massachusetts, a colony taken under a broad stone in an open clump of young white pine, which was nesting beside two species of open-woods ants (Lasius alienus and Aphaenogaster picea).

New Mexico
This species nests under stones in moist areas. Colonies apparently consist of only a few workers. They prey primarily on chilopods. These secretive ants are rarely collected, but well worth the search (Mackay and Mackay 2002)

Foraging/Diet
The highly modified mandibles appear to be specialized for hunting centipedes. Predators of centipedes and beetle larvae in forest litter.

Associations with other Organisms
It is possible that Strumigenys species are most often found under the same stone.

Common Name
Pale Footed Primitive Ant

Nomenclature

 *  pallipes. Typhlopone pallipes Haldeman, 1844: 54 (w.) U.S.A. Emery, 1895c: 261 (q.m.); Wheeler, G.C. & Wheeler, J. 1952a: 114 (l.). Combination in Amblyopone: Haldeman, 1849a: 201 (footnote); in Stigmatomma: Roger, 1863b: 20; in Amblyopone: Brown, 1960a: 169; in Stigmatomma: Yoshimura & Fisher, 2012: 19. [Stigmatomma pallidipes: Dalla Torre, 1893: 14, unjustified emendation.] Senior synonym of serratum: Mayr, 1886d: 439; of binodosus: Emery, 1895c: 261; of arizonense, wheeleri: Creighton, 1940b: 3; of montigena: Brown, 1949c: 84; of subterranea: Brown, 1960a: 169. See also: Whelden, 1958: 1; Traniello, 1982: 65.
 * serratum. Stigmatomma serratum Roger, 1859: 251 (w.) U.S.A. Junior synonym of pallipes: Mayr, 1886d: 439.
 * binodosus. Arotropus binodosus Provancher, 1881a: 206, figs. 32, 33 (q.) CANADA. Provancher, 1887: 240 (w.). Combination in Amblyopone: Provancher, 1887: 240; in Stigmatomma: Dalla Torre, 1893: 14. Junior synonym of pallipes: Emery, 1895c: 261.
 * wheeleri. Stigmatomma pallidipes [sic] var. wheeleri Santschi, 1914a: 429 (w.q.m.) U.S.A. Junior synonym of pallipes: Creighton, 1940b: 3.
 * arizonense. Stigmatomma pallipes subsp. arizonense Wheeler, W.M. 1915b: 389 (w.) U.S.A. Junior synonym of pallipes: Creighton, 1940b: 3.
 * montigena. Stigmatomma pallipes subsp. montigena Creighton, 1940b: 7 (w.q.) U.S.A. Subspecies of pallipes: Creighton, 1950a: 33. Junior synonym of pallipes: Brown, 1949c: 84; Brown, 1960a: 169.
 * subterranea. Stigmatomma pallipes subsp. subterranea Creighton, 1940b: 8 (w.) U.S.A. Raised to species: Brown, 1949c: 85. Junior synonym of pallipes: Brown, 1960a: 169.

Worker
Minutely punctured, dull reddish-brown, terminal segments of the abdomen, antennae, and mandibles, paler; legs testaceous. 6 mill. long. Head subquadrate, narrowing posteriorly; mandibles widest in the middle, direct, with the tip incurved, inner margin coarsely serrate-dentate: pronotum inflated, with an impressed mesial line : abdomen divided into three principal segments, of which the first is subglobular, the second considerably larger, conical, largest posteriorly, terminal segment of equal diameter with the preceding, but twice as long, with a dark indistinct transverse band about the middle: provided with a sting.

Queen
Emery (1895) - Das ♀ ist nicht grosser als die ♀♀, ja sogar kleiner als mein grösster ♀ sonst, abgesehen von den grösseren Augen sowie der Anwesenheit der Punktaugen und der Flügel, vom ♀ nicht verschieden

Male
Emery (1895) - Das ♂ ist dem von Forel beschriebenen S. gheorgieffi sehr ähnlich und nur in folgenden Punkten von der Beschreibung abweichend: der Clypeus hat eine grössere Zahl sehr kleiner Zähne; die Fühler sind weniger schlank, nur das 2. Geisselglied ist mehr als doppelt so lang wie dick, die übrigen weniger als zweimal so lang wie dick; das Mesonotum ist durchaus matt, die Seiten des Thorax wenig glänzend, das Scutellum glänzend, die seitlich gerandete, flache, abschüssige Fläche des Metanotums kaum glänzend. Das Stielchen des Abdomens ziemlich grob runzlig punktirt, daher minder glänzend als diefolgenden Segmente. Pechschwarz. Mundtheile, Fühler, Beine und Genitalien gelbbraun, die Schenkel etwas dunkler.

Etymology
Pale-footed