Crematogaster depilis

This species nests at base of desert shrubs (Eriogonum, Larrea, Opuntia, Yucca, Dasylirion, Hamatocactus, Franseria, Ephedra) or in the branches of mesquite. Nests are occasionally found under stones or under cattle manure. Brood is present in nests in August and September. It is primarily an individual forager which collect nectar from flowers, or tends scale insects. They are often found foraging on cholla (Opuntia spp.), and occasionally on oaks. (Mackay and Mackay 2002)

Identification
Morgan & Mackay (2017) - The key characteristic of C. depilis is the complete lack of erect hairs on the entire dorsum of the mesosoma. Crematogaster depilis is distinctly punctate on both dorsum and sides of the mesosoma. The worker has a postpetiole with well-defined hemilobes, is relatively large for this genus, and can generally be found nesting in the roots of desert shrubs such as Opuntia sp. and Larrea tridentata.

Crematogaster depilis could be easily confused with Crematogaster opaca, as the mesosomata of both species are punctated and opaque. They can be easily separated as the dorsal surface of the head of C. depilis is partially smooth and shiny, and is completely or mostly punctate and opaque in C. opaca. It might be confused with Crematogaster corvina, which has at least 2 erect hairs on the mesosoma.

Distribution
Southern California and east to Texas, south to northern Mexico.

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

Habitat
Mackay and Mackay (2002) - Desert communities, except grasslands without shrubs, creosotebush scrub, mesquite forests, up into pinyon-juniper and oak woodlands (2100 meters elevation).

Biology
Nevada, Wheeler and Wheeler (1986) - One nest was under a stone; for all other records (when data were given) the workers were at the base of desert plants (1 Eriogonum, 4 Larrea, 1 Opuntia, 1 Yucca).

Morgan & Mackay (2017) - Mackay and Mackay (unpublished) have collected extensive data on this species. Crematogaster depilis nests in the lower branches and roots of small desert shrubs, sotol and cacti (especially cholla), and especially in those of the creosotebush Larrea tridentata (Mackay et al., 1984), in the larval galleries of wood and stem boring beetles. It is also found under stones and in yucca logs. Occasionally it simply nests in open soil, usually with a small mound. To find this ant, look in shrubs (especially creosotebush) that have dead branches that come from the base of the plant.

Brood were found in nests in June and August, sexuals in June and July. Sexuals were attracted to blacklights in June and July, founding females found in March and June. Workers are usually timid, but large nests can be aggressive, although the workers do not often bite.

Crematogaster depilis forages diurnally and nocturnally, on the ground and in vegetation including cholla, creosotebushes, and oak (Quercus arizonica). It is very common foraging on Larrea tridentata and Opuntia sp. in the late afternoon and can be found on the extrafloral nectaries of Opuntia sp. These ants readily come to baits on the soil surface, subterranean and in the vegetation, including Vienna sausage (cholla, Yucca, Prosopis) or cookie baits and are often found in pitfall traps. They also feed on dead insects.

They commonly visit the extrafloral nectaries of the barrel cactus Ferocactus acanthodes (Ruffner and Clark, 1986) and F. gracilis and nest near the base of the cactus (Blom and Clark, 1980). They also visit extrafloral nectaries of the senita cactus Pachycereus schottii (Chamberlain and Holland, 2008) as well as Cylindropuntia arbuscula and C. bigelovii (Chamberlain and Holland, 2009). It is the dominant consumer in a guild of 14 ant species (Holland et al., 2009, 2010). They are usually subordinate to ants of the subfamily Dolichoderinae, but achieve dominance where the latter are poorly represented (Bestelmeyer, 2005).

They are found in grasslands, creosotebush scrub, thorn scrub, mesquite shrublands, riparian shrubland, sagebrush, oak forests, pinyon juniper and pine forests (Mackay and Mackay, unpublished). Bestelmeyer and Wiens, (2001a) reported them from shrublands, associated with creosote bush plants (Bestelmeyer and Wiens, 2001b). Whitford et al., (1999) found them in creosote bush communities as well as shrubland mosaics and tarbush shrubland.

Crematogaster depilis is found in several soil types ranging from red clay, purple-gray fine sand/clay, red-purple fine sandy loam, rocky loam, light brown sand, light brown rocky sand to red and light brown rocky gravel.

Myrmecophila sp. crickets and various beetles are found in nests (Mackay and Mackay, unpublished).

Nomenclature

 *  depilis. Crematogaster opaca var. depilis Wheeler, W.M. 1919g: 111 (w.) U.S.A.
 * [First available use of Crematogaster lineolata subsp. opaca var. depilis Wheeler, W.M. 1908e: 478; unavailable name.]
 * Wheeler, G.C. & Wheeler, J. 1973a: 28 (l.).
 * Combination in C. (Acrocoelia): Emery, 1922e: 141.
 * Combination in C. (Crematogaster): Buren, 1968b: 93.
 * Subspecies of punctulata: Enzmann, J. 1946c: 93.
 * Raised to species: Creighton, 1950a: 209; Buren, in Smith, M.R. 1958c: 126.
 * Senior synonym of larreae: Junior synonym of depilis: Morgan & Mackay, 2017: 155.
 * larreae. Crematogaster (Crematogaster) larreae Buren, 1968b: 117 (w.q.m.) U.S.A.
 * Junior synonym of depilis: Morgan & Mackay, 2017: 155.

Crematogaster larreae
The type locality of this new species is El Paso, Tex., where it may be found commonly nesting in the lower stems and roots of the desert plant, Larrea divaricata Cav., growing on the compacted rocky aluvial washes surrounding the bases of the Franklin Mts. I have found C. larreae in numerous specimens of this plant on a number of occasions at El Paso and have taken males and females at lights in El Paso. I have also captured the species at Van Horn, Tex., 10 mi. E. of Gila Bend, Ariz., and at Yucca Grove, Calif., all of these specimens from lower stems and roots of Larrea. I have chosen a male taken with workers at El Paso to be the holotype and all the other specimens, including the winged forms at lights, are marked as paratypes.

Holotype and several paratypes of each sex will be deposited in the National Musem, but I will retain most of the paratypes.

Taxonomic Notes
Morgan & Mackay (2017) - We have examined the original series of C. larreae collected by William Buren from the west slope of Mt. Franklin in El Paso, Texas and found the series to be a mixture of C. depilis and C. larreae. Some were definitely concolorous dark brown, some were definitely bicolored with lighter colored head, mesosoma, petiole and postpetiole and dark gaster. Some, however, could be placed in either group where the distinction between light head and dark gaster were not very profound. Some specimens had a small sternopetiolar tooth, but it was absent on other specimens. Types of these two taxa are indistinguishable and we have examined nest series that are mixtures from the Indio Mountains Research Station. These observations lead us to conclude that Crematogaster larreae is a junior synonym of Crematogaster depilis.