Temnothorax

The workers of Temnothorax species are generally small. Colonies are typically monogynous, although facultative polygyny has been documented in several species (Alloway et al. 1983, Buschinger 1974, Buschinger and Linksvayer 2004, Rüppell et al. 1998). Colony populations are usually quite small, often with less than 100 workers (Beckers et al. 1989). However, several studies have found colonies of some species to be widely dispersed with several to many satellite nests (Alloway et al. 1983, Foitzik and Heinze 2001, Partridge et al. 1997). Many species are arboreal, living within hollow stems, old beetle or termite galleries, or in galls (Mackay 2000). Temnothorax species appear to be trophic generalists, feeding on a wide variety of scavenged items, including the elaiosomes of seeds (Espadaler 1997, Fokuhl et al. 2012). None have been documented to be active or aggressive predators. (Snelling et al. 2014)

The socially parasitic species formerly placed in the genus Myrmoxenus (synonymised with Temnothorax by Ward et al., 2014) vary strongly in fundamental life history traits, such as queen-worker ratio, the timing of sexual production, and mating behavior. Queens of these species generally take over nests of other Temnothorax species, kill the resident queen by throttling, and force the workers to take care of the social parasite’s brood. Young queens of Temnothorax ravouxi and other species produce large numbers of workers, which during “slaveraids” pillage host pupae from neighboring Temnothorax host colonies to increase the workforce in their own nests. Other species, such as Temnothorax corsicus, have lost caste polyphenism and rear only male and female sexual offspring. (Heinze et al., 2015.)

Identification
Antennal count is typically twelve segments but there are a small number of species with only eleven.

New World Temnothorax species groups

Eguchi, Bui and Yamane (2011) - The worker of Temnothorax is similar to that of Vombisidris and Cardiocondyla.

Biology
Matthew Prebus is actively investigating the systematics and biology of the genus. The following is from a recent study (Prebus 2017, see this publication for citations):

General Biology
While the biology of most species of Temnothorax is poorly known, several taxa are frequently used as model organisms for social insect behavior and ecology. Studies on this genus have led investigators to discover new forms of social learning and inspired hypotheses about speciation and the origins of parasitism.

Temnothorax has a primarily Holarctic distribution, but notable exceptions include several species in Sub-Saharan Africa and many species in Mesoamerica, including the islands of the Caribbean. Generally, Temnothorax ants are encountered in the mesic forests of the Northern hemisphere at mid-to-high elevations, where they are typically found under rocks, in leaf litter, or as arboreal foragers. However, these ants have adapted to a broad variety of habitats, from arid deserts to tropical rain forests, and are found at elevations from sea level up to 4000 m. The workers of most species in the Holarctic region are diminutive, timid, slow moving, and cryptically colored. Because of their inconspicuous nature, these ants are often overlooked despite their broad geographical distribution. The islands of the Greater Antilles harbor many Temnothorax endemics, however, that provide an exception to this habitus: the islands Cuba and Hispaniola, for example, have more than thirty described endemic species, which are large, brightly colored, and capable of delivering powerful stings.

Temnothorax ants are believed to be trophic generalists, and have been observed scavenging for a variety of food items, including dead insects, honeydew on leaves without tending aphids, honeydew from tended aphids and membracids, the axillary nectaries of bracken ferns and Baccharis (an Asteraceae genus), seeds, and elaiosomes. In competitions at baits, they appear to be opportunistic foragers, often absconding as more aggressive species arrive, and occasionally insinuating themselves into baits dominated by other species (Prebus, pers. obs.). Recruitment of workers to food and nest sites often appears to involve tandem running.

Nests of Temnothorax are generally small, often with fewer than 200 workers, which may be distributed among several satellite nests. With the worker caste of most species measuring less than four millimeters in length, these ants often take advantage of small cavities for their nesting sites, such as crevices in rocks, hollow nut shells, dead twigs, or directly in the soil. Temnothorax colonies tend to be monogynous, with only one queen per nest. This is hardly the rule, however: this genus displays a remarkable diversity of sociometry, with many species being either functionally monogynous (with several queens present, but only one actively producing eggs), or facultatively polygynous, both within and among species.

Many species appear to be arboreal specialists, nesting in dead hollow twigs on live trees, under bark, in galls, or under the roots of epiphytes.

Several taxa have intriguing life histories: it appears that Temnothorax and its sister group, the Leptothorax genus group (composed of Formicoxenus, Harpagoxenus, and Leptothorax) are unusually prone to developing a set of interrelated lifestyles collectively known as ‘social parasitism’.

Phylogeny and Biogeography
Molecular analyses suggested the genus first arose 35Ma, with an initial succession of rapid diversification into distinctive clades. Early diversification occurred in the Neartic with large scale dispersal (Carribean, Neotropical mainland, Palearctic) following soon after the formation of the initial clades. The phylogeny clarifies and resolves numerous long standing problems with various past generic, subgeneric and species-group hypotheses. The data show support for Temnothorax originating as a terrestrial nesting species that later evolved arboreal species. Parasitism appears to have arisen numerous times, as it is not confined to a single node of the phylogeny.

Eguchi, Bui and Yamane (2011) - Temnothorax species are rare in Vietnam where they have been collected around or above 1000 m alt. in northern Vietnam.

Nomenclature

 *  TEMNOTHORAX [Myrmicinae: Formicoxenini]
 * Temnothorax Mayr, 1861: 68. Type-species: Myrmica recedens, by monotypy.
 * Temnothorax junior synonym of Leptothorax: Forel, 1890a: lxxii.
 * Temnothorax revived from synonymy as subgenus of Leptothorax: Forel, 1892i: 315; maintained as subgenus: Emery, 1915g: 24; Forel, 1915d: 27; Bondroit, 1918: 117; Wheeler, W.M. 1922a: 679; Emery, 1924d: 259.
 * Temnothorax junior synonym of Leptothorax: Baroni Urbani, 1971c: 96; Bolton, 1982: 319; Bolton, 1994: 105.
 * Temnothorax revived status as genus: Bernard, 1967: 185; Arnol'di & Dlussky, 1978: 543; Dlussky & Fedoseeva, 1988: 79; Atanasov & Dlussky, 1992: 125; Bolton, 2003: 252, 270.
 * Temnothorax senior synonym of Antillaemyrmex, Croesomyrmex, Dichothorax, Icothorax, Macromischa, Myrmammophilus, Myrafant: Bolton, 2003: 252, 270.
 * Current subgenera of Temnothorax: nominal plus  Gonepimyrma. 
 * ANTILLAEMYRMEX [junior synonym of Temnothorax]
 * Antillaemyrmex Mann, 1920: 408 [as subgenus of Macromischa]. Type-species: Macromischa (Antillaemyrmex) terricola, by original designation.
 * Antillaemyrmex raised to genus: Wheeler, W.M. 1931b: 4 (in text).
 * Antillaemyrmex junior synonym of Macromischa: Smith, M.R. 1937: 849; Smith, M.R. 1939e: 502.
 * Antillaemyrmex junior synonym of Leptothorax: Snelling, R.R. 1986: 154.
 * Antillaemyrmex junior synonym of Temnothorax: Bolton, 2003: 253, 271.
 * CHALEPOXENUS [junior synonym of Temnothorax]
 * Chalepoxenus Menozzi, 1923a: 257. Type-species: Chalepoxenus gribodoi (junior synonym of Leptothorax muellerianus), by monotypy.
 * [Name of type-species initially misspelled gridoboi, p. 257; correct spelling as gribodoi, p. 258.]
 * Chalepoxenus senior synonym of Leonomyrma: Buschinger, 1987: 117.
 * Chalepoxenus junior synonym of Temnothorax: Ward et al., 2014: 15.
 * CROESOMYRMEX [junior synonym of Temnothorax]
 * Croesomyrmex Mann, 1920: 408 [as subgenus of Macromischa]. Type-species: Macromischa (Croesomyrmex) wheeleri, by original designation.
 * Croesomyrmex raised to genus: Wheeler, W.M. 1931b: 4 (in text).
 * Croesomyrmex junior synonym of Macromischa: Smith, M.R. 1937: 849; Smith, M.R. 1939e: 502.
 * Croesomyrmex junior synonym of Temnothorax: Bolton, 2003: 253, 271.
 * DICHOTHORAX [junior synonym of Temnothorax]
 * Dichothorax Emery, 1895c: 323 [as subgenus of Leptothorax]. Type-species: Leptothorax (Dichothorax) pergandei, by subsequent designation of Wheeler, W.M. 1911f: 161.
 * Dichothorax raised to genus: Ashmead, 1905b: 383.
 * Dichothorax subgenus of Leptothorax: Wheeler, W.M. 1910g: 139.
 * Dichothorax junior synonym of Leptothorax: Bolton, 1982: 319.
 * Dichothorax junior synonym of Temnothorax: Bolton, 2003: 253, 271.
 * EPIMYRMA [junior synonym of Myrmoxenus]
 * Epimyrma Emery, 1915a: 262. Type-species: Epimyrma kraussei, by original designation.
 * Epimyrma senior synonym of Myrmoxenus (and its junior synonym Myrmetaerus): Buschinger, 1990: 245 (provisional synoynym); Bolton, 1994: 105 [incorrect seniority].
 * Epimyrma junior synonym of Myrmoxenus: Schulz & Sanetra, 2002: 162.
 * ICOTHORAX [junior synonym of Temnothorax]
 * Icothorax Hamann & Klemm, 1967: 415 [as subgenus of Leptothorax]. Type-species: Leptothorax (Icothorax) megalops, by monotypy.
 * Icothorax junior synonym of Myrafant: Baroni Urbani, 1978b: 556; Bolton, 1995b: 32.
 * Icothorax junior synonym of Chalepoxenus: Hölldobler & Wilson, 1990: 13.
 * Icothorax junior synonym of Temnothorax: Bolton, 2003: 253, 271.
 * LEONOMYRMA [junior synonym of Chalepoxenus]
 * Leonomyrma Arnol'di, 1968: 1809. Type-species: Leonomyrma spinosa, by original designation.
 * Leonomyrma junior synonym of Chalepoxenus: Buschinger, 1987: 117.
 * MACROMISCHA [junior synonym of Temnothorax]
 * Macromischa Roger, 1863a: 184. Type-species: Macromischa purpurata, by subsequent designation of Wheeler, W.M. 1911f: 166.
 * Macromischa subgenus of Leptothorax: Baroni Urbani, 1978b: 398.
 * Macromischa revived status as genus: Smith, D.R. 1979: 1390.
 * Macromischa senior synonym of Antillaemyrmex, Croesomyrmex: Smith, M.R. 1937: 849; Smith, M.R. 1939e: 502; Baroni Urbani, 1978b: 398.
 * Macromischa junior synonym of Leptothorax: Snelling, R.R. 1986: 154; Bolton, 1994: 105; Bolton, 1995b: 34.
 * Macromischa junior synonym of Temnothorax: Bolton, 2003: 252, 271.
 * MYRAFANT [junior synonym of Temnothorax]
 * Myrafant Smith, M.R. 1950: 30 [as subgenus of Leptothorax]. Type-species: Leptothorax curvispinosus, by original designation.
 * Myrafant senior synonym of Icothorax: Baroni Urbani, 1978b: 556.
 * Myrafant junior synonym of Leptothorax: Bolton, 1982: 319.
 * Myrafant junior synonym of Temnothorax: Bolton, 2003: 253, 271.
 * MYRMAMMOPHILUS [junior synonym of Temnothorax]
 * Myrmammophilus Menozzi, 1925d: 29 [as subgenus of Leptothorax]. Type-species: Leptothorax (Myrmammophilus) finzii, by monotypy.
 * Myrmammophilus junior synonym of Leptothorax: Bolton, 1982: 319.
 * Myrmammophilus junior synonym of Temnothorax: Bolton, 2003: 253, 271.
 * MYRMETAERUS [junior synonym of Myrmoxenus]
 * Myrmetaerus Soudek, 1925a: 33. Type-species: Myrmetaerus microcellatus (junior synonym of Myrmoxenus gordiagini), by monotypy.
 * [Myrmetaerus also described as new by Soudek, 1925b: 14.]
 * Myrmetaerus junior synonym of Camponotus: Snelling, R.R. 1981: 404 (error).
 * Myrmoxenus junior synonym of Epimyrma: Bolton, 1994: 105.
 * Myrmetaerus junior synonym of Myrmoxenus: Buschinger, Winter & Faber, 1984: 336; Bolton, 2003: 248.
 * MYRMOXENUS [junior synonym of Temnothorax]
 * Myrmoxenus Ruzsky, 1902b: 474. Type-species: Myrmoxenus gordiagini, by monotypy.
 * Myrmoxenus senior synonym of Myrmetaerus: Buschinger, Winter & Faber, 1984: 336.
 * Myrmoxenus junior synonym of Epimyrma: Bolton, 1994: 105 [incorrect seniority].
 * Myrmoxenus senior synonym of Epimyrma: Schulz & Sanetra, 2002: 162.
 * Myrmoxenus junior synonym of Temnothorax: Ward et al., 2014: 15.
 * PROTOMOGNATHUS [junior synonym of Temnothorax]
 * Protomognathus Wheeler, W.M. 1905a: 3 [as subgenus of Tomognathus]. Type-species: Tomognathus americanus, by monotypy.
 * Protomognathus junior synonym of Harpagoxenus: Emery, 1924d: 265.
 * Protomognathus revived from synonymy and raised to genus: Cover, in Hölldobler & Wilson, 1990: 65.
 * Protomognathus junior synonym of Temnothorax: Ward et al., 2014: 15.