Brachymyrmex depilis

Colonies or nest chambers that form part of a nest of Brachymyrmex depilis can be found in the soil under stones or in rotting wood in a wide variety of habitats: open forest, dense moist forest, grasslands, and fields. The workers lead almost wholly subterranean lives. In addition to being general scavengers workers also tend root aphids and coccids in underground galleries. The gastral tergites of Brachymyrmex depilis workers have flexible connections that permit their gaster to easily expand and contract. Their crops can be filled with a large amount of liquid, at least relative to the overall size of a worker.

Identification
Very small yellow ants. Their color distinguishes this species from other named North American Brachymyrmex, which vary from grey to dark brown. The genus can be readily separated from other Formicinae by the combination of their small size, hair fringed acidophore, and 9 segmented antenna.

Distribution
Range United States, S Canada, Mexico. Most U.S. states and south into Mexico. This species is putatively wide ranging. A badly needed taxonomic revision of the North America forms will likely reveal Brachymyrmex depilis is a number of distinctive species.

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

Biology
Brachymyrmex depilis are opportunistic nesters, making galleries in downed wood, at the base of living vegetation, under bark, under stones, in litter, along roots and in the soil. Their small size and thin integument means individuals desiccate quickly, leading colonies to settle in places where they can have humid nest chambers.

Headley (1943) reported finding nests of Brachymyrmex depilis in Oak acorns.

Nomenclature

 *  depilis. Brachymyrmex heeri subsp. depilis Emery, 1893i: 635 (w.q.) U.S.A. Wheeler, G.C. & Wheeler, J. 1953c: 139 (l.). Raised to species: Santschi, 1923b: 663. Senior synonym of nanellus: Creighton, 1950a: 359; of flavescens: Cole, 1953g: 266.
 * nanellus. Brachymyrmex nanellus Wheeler, W.M. 1903b: 102, fig. 7b (w.m.) U.S.A.
 * Junior synonym of depilis: Creighton, 1950a: 359; Ortiz-Sepulveda et al., 2019: 46.
 * flavescens. Brachymyrmex depilis subsp. flavescens Grundmann, 1952: 117 (w.) U.S.A.
 * Junior synonym of depilis: Cole, 1953g: 266; Ortiz-Sepulveda et al., 2019: 46.

Etymology
Descriptive. depilis = "without hair"