Odontomachus clarus

Identification
Brown (1976) - Odontomachus clarus is like Odontomachus insularis, and it also shares with insularis the dark-colored male and 4, 3 palpal segmentation. In fact, the only reliable worker character I can find to separate the two is the different development of the acute apex of the petiolar node. In insularis, the node narrows fairly abruptly (in side view) to a long, thin, backcurved spine, which may occupy a quarter or more of the total height of the node. In O. clarus, the node as seen from the side tapers rapidly to a much shorter spine, which often is not really a spine at all, but simply a sharp conical apex. The shortest and most stumpy nodes tend to occur in small, pale yellowish-brown individuals from the northern limits of the species in Central Texas, and especially in the mountains of southeastern Arizona (Huachuca, Chiricahua and Santa Rita Mountains at altitudes of 1000- 1500 m., for example).

Distribution
Southwestern North America from Arizona and New Mexico to southern Mexico and a disjunct occurrence in Florida.

This taxon was described from U.S.A.

Biology
Nests are often found under rocks or in grasses associated with both arid and mesic habitats. They have also been located under downed trees in fine sand and gravel soils (Smith 1939, Cokendolpher & Francke 1990, Deyrup and Cover 2004).

Louisiana
Adams et al. (2010) - "On 11 August 2009 two head capsules were collected in the midden pile of a colony of Dorymyrmex flavus McCookon the road near the Corral Camp area of the Kisatchie National Forest in Central Louisiana (31°31.774’N 093°03.510’W Elev. 323’). The head capsules were missing the recognizable jaws but the converging dorsal furrows on the capsules matched the characters of Odontomachus (Deyrup et al. 1985, Brown 1976). Coloration and head size indicated a species other than the non-native Odontomachus haematodus (Linnaeus), already known to exist in southeastern Louisiana. Presence of the capsules within the midden pile indicate possible predation of Odontomachus by Dorymyrmex. Aggressive interaction between Dorymyrmex bureni (Trager) and O. brunneus has previously been reported by Wild (in Deyrup and Cover 2004). An Odontomachus colony was located on 26 March 2010 in the Kisatchie district of Kisatchie National Forest on the Long Leaf Vista trail (31°28.576’N 092°59.683’W Elev. 238’). Three workers were collected under a rock in sandy soil at the base of a rock bluff. Workers were hand collected and stored in ethanol. Another colony was located on 18 June 2010 near Corral Camp (31°32.105’N 093°03.403’W Elev. 270’) under a large rock next to a rotting stump near the road. The entire colony was collected, including workers and male and female alates. Vouchers are deposited in the Louisiana State Arthropod Museum."

Nomenclature

 *  clarus. Odontomachus clarus Roger, 1861a: 26 (w.) U.S.A. Patton, 1894: 618 (m.); Wheeler, W.M. 1908e: 407 (q.); Petralia & Vinson, 1980: 381 (l.). Subspecies of haematodus: Emery, 1911d: 115; Wheeler, W.M. 1914b: 40; Smith, M.R. 1939d: 129. Revived status as species: Taylor & Wilson, 1962: 142; Brown, 1976a: 136. Senior synonym of clarionensis: Taylor & Wilson, 1962: 142; of coninodis, desertorum: Brown, 1976a: 103; of texana: Wheeler, W.M. 1902f: 26. See also: Deyrup, Trager & Carlin, 1985: 192.
 * texana. Odontomachus texana Buckley, 1867: 335 (w.) U.S.A. Junior synonym of insularis: Emery, 1895c: 268; of clarus: Wheeler, W.M. 1902f: 26.
 * coninodis. Odontomachus haematodus subsp. coninodis Wheeler, W.M. 1915b: 391 (w.q.) U.S.A. Junior synonym of clarus: Brown, 1976a: 103. See also: Smith, M.R. 1939d: 128.
 * desertorum. Odontomachus haematoda subsp. desertorum Wheeler, W.M. 1915b: 391 (w.) U.S.A. Junior synonym of clarus: Brown, 1976a: 103. See also: Smith, M.R. 1939d: 128.
 * clarionensis. Odontomachus haematoda subsp. clarionensis Wheeler, W.M. 1934f: 141 (w.) MEXICO. Junior synonym of clarus: Taylor & Wilson, 1962: 142.

Brown (1976) - In Odontomachus clarus, the node as seen from the side tapers rapidly to a much shorter spine, which often is not really a spine at all, but simply a sharp conical apex. The shortest and most stumpy nodes tend to occur in small, pale yellowish-brown individuals from the northern limits of the species in Central Texas, and especially in the mountains of southeastern Arizona (Huachuca, Chiricahua and Santa Rita Mountains at altitudes of 1000- 1500 m., for examples). The mountain samples have been considered as a separate subspecies coninodis, but I see no need to give a formal name to these depauperate ecotypes or ecophenotypes occurring at the upland range boundary of a variable species. Samples from nearby Tucson, taken at lower altitudes in the desert (types of subsp. desertorum) are large, richly colored, and similar to samples of O. clarus from much farther south in Mexico; I do not hesitate to call them conspecific without making further distinction. A transect of collections taken from the Sonoran desert flats up into the mountains should establish clines connecting the lowland and upland forms. Until this transect is properly established, there will of course remain some doubt as to whether the upland form might be a local species. The subspecies clarionensis is based on a worker from Clarion Island, far out in the Pacific of Mexico. This worker proves to be a rather typical specimen of O. clarus, as already indicated by Taylor and Wilson (1961) without comment.

Additional References

 * B. J. Adams, X. Chen and L. M. Hooper-Bùi, "Odontomachus clarus Roger (Hymenoptera: Formicidae) reported in Kisatchie National Forest, Louisiana," [Midsouth Entomologist, vol. 3, no. pp. 104-105, 2010].