Odontomachus relictus

Described from specimens collected in scrub and sandhill habitats on several ancient sand ridges in Florida. It appears to be a relict species from dry periods in the Pleistocene (Deyrup and Cover 2004).

Identification
Distinguished from other U.S. Odontomachus by the following combination of character states: conspicuous striae present on basalar lobe (oval sclerite at dorsal posterior corner of mesopleuron); posterior side of petiole without transverse striae; appressed hair on first gastral tergite sparse, short, spaces between hairs often as wide as the length of hairs. Male - Distinguished from other U.S. Odontomachus by the following combination of character states: ocelli very large, wider than the distance between the lateral ocelli and the eyes; body color medium brown, antennae yellowish. (Deyrup and Cover 2004)

Identification Keys including this Taxon

 * Key to US Odontomachus species

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



Biology
Deyrup and Cover (2004) - This species is a subterranean nester, and found only in areas of deep, unconsolidated, silica sand. These areas may be covered with Florida scrub vegetation, consisting of scattered pines, small oaks and other small trees and shrubs. Sometimes there are areas of bare sand, especially in the first few years following a fire. Alternatively, areas where relictus occurs may be sandhill vegetation, consisting of scattered pines above a low layer of grasses and forbs. For descriptions of these habitats, see Myers (1990). Nest entrances are not marked by a mound, but by scattered pellets of sand. Digging into a nest may produce a few workers, sometimes with brood, but no large aggregation of workers.

Odontomachus relictus is known from the Lake Wales Ridge, the southern Brooksville Ridge and the Orlando Ridge. It has not been found in scrub or sandhill habitats on the Atlantic Coastal Ridge, the Northern Brooksville Ridge, or the sandy uplands of northern Florida. The inland south-central sand ridges of the Florida Peninsula are over a million years old, and are known to have many plants and animals found nowhere else (Deyrup 1989, 1990). Some of these species appear to be remnant populations of species that were once more widespread, others are probably true (autochthonous) endemics. Up to the discovery of the distinct status of O. relictus, it seemed that this ant was an example of a series of remnant populations; now it appears that this species could just as easily be a true endemic of south-central Florida.

The restricted range and habitat of O. relictus might raise questions about its conservation status. About twenty-five years ago, its prospects would have seemed poor. At that time there were only two protected populations, one on the Lake Wales Ridge (Archbold Biological Station), the other on the southern Brooksville Ridge (Withlacoochee State Forest). Upland areas were being converted rapidly to housing and agriculture, and it seemed that few scrub and sandhill areas would remain within the range of O. relictus. Since that time, development and habitat destruction have occurred at an unprecedented rate, but the establishment of ecological preserves also has been remarkably fast, especially on the Lake Wales Ridge. This species now appears to be adequately protected, unless it is subjected to some widespread environmental threat that pervades natural areas. Odontomachus relictus is a good example of a species that seemed destined for the endangered species list, with all the trouble and expense implied in such listing, but was preemptively protected by more general conservation programs.

Nomenclature

 *  relictus. Odontomachus relictus Deyrup & Cover, 2004b: 137, figs. 1, 2A (w.q.m.) U.S.A.

Worker
Holotype - Features visible in lateral view described from left side. Measurements in mm. Total length (length of head excluding mandibles + length of mesosoma + length of petiole + length of gaster): 7.48; head length: 2.12; width of head at rear margins of eyes: 1.80; width of head at widest part of occipital lobes: 1.62; length of left mandible: 1.20; maximum width of eye: 0.30; maximum width of clypeal area: 0.30; length of mesosoma: 2.67; length of petiole: 0.52; length of gaster: 2.17. Head: fine striae diverging from frontal lobes, covering frontal aspect of head, disappearing before occipital area, covering only the upper quarter of the extraocular furrow; posterior lateral corners, occipital area, underside of head smooth and shining. Mesosoma: pronotum with roughly circular concentric striae, without longitudinal striae reaching the hind margin; mesonotum and propodeum with transverse striae; striae present on basalar lobe; mesopleuron smooth, shining, with longitudinal striae along dorsal and ventral margins. Petiole: apically spinose; in profile anterior face convex, posterior face bisinuate; posterior face in posterior view smooth and shining, without hairs. Gaster: shining, no surface sculpture except for minute punctures from which hairs emerge; first tergite sparsely covered with short, appressed, pale hairs, spaces between hairs usually as wide as length of hairs; first tergite with sparse, scattered, suberect long hairs, including an uneven subapical row. Color: head, antennae, mesosoma, petiole dark reddish brown, contrasting with blackish-brown gaster; legs dark yellow, contrasting with mesosoma.

Queen
Paratype - Measurements in mm. Total length (length of head excluding mandibles + length of mesosoma + length of petiole + length of gaster): 8.37; head length: 2.15; width of head at rear margins of eyes: 1.77; width of head at widest part of occipital lobes: 1.70; length of left mandible: 1.20; maximum width of eye: 0.27; maximum width of clypeal area 0.25; length of mesosoma: 2.75; length of petiole: 0.52; length of gaster: 2.95. Structural character states and color as in worker, except for occurrence of ocelli and expansion of the mesosomal dorsum (pronotum, mesonotum, scutellum) associated with flight; pronotum transversely striate, mesonotum longitudinally striate.

Male
Paratype - Measurements in mm. Total length (length of head excluding mandibles + length of mesosoma + length of petiole + length of gaster): 6.66; head length: 1.07; width of head at widest part, including eyes:1.45; length of mesosoma: 2.25; length of forewing: 4.95; length of petiole: 0.47; length of gaster: 2.57. Head: in frontal view, eyes longer than the distance between them dorsally; median ocellus wider than the distance between a lateral ocellus and the margin of the eye; clypeus in profile not strongly protuberent. Mesosoma: pronotum, mesopleural area above and below episternal suture feebly shining, not striate; mesonotum finely striate, transversely on anterior quarter, remainder longitudinally; scutellum convex, shining, lacking a median carina; propodeum without a raised carina, feebly shining, with weak, fine striae in the following patterns: a median series of concentric ovals, posterior portion with transverse bisinuate lines, obliquely longitudinal lines laterally ventral to spiracle; propodeum in profile long and low, without a declivitous posterior portion; gaster shining, tergites without surface sculpture except for fine, hair-bearing punctures, evenly covered with long, fine, sub-appressed hairs.

Type Material
Holotype, 3 paratype dealate queens, 32 paratype workers, 12 paratype males: Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts; 6 paratype workers, 4 paratype males: The Natural History Museum, London; 7 paratype workers, 4 paratype males: Los Angeles County Museum, Los Angeles, California; 10 paratype workers, 4 paratype males: Florida State Collection of Arthropods, Gainesville, Florida; remaining type material in the arthropod collection of the Archbold Biological Station, Lake Placid, Florida.

Holotype Worker. FL: Highlands Co., Archbold Biological Station, 15-IV-1996, M. Deyrup, recently burned mature scrub, Red Hill, nest in sand. Paratype dealate queen used for description of queen (designated on label). Same locality, collector as holotype, 18-I-1983, Florida scrub habitat with Ceratiola ericoides, E. side of Tract 7. Paratype male used for description of male (designated on label). Same locality, collector as holotype, 8-XI-1990, at window, main building. Paratype workers and queens (all from Florida). The following specimens all have the same locality and collector as the holotype: 18 workers: same data as holotype (nest series with holotype).

Etymology
relictus, past participle of relinquo: left behind, referring to the distribution of the species on relict patches of Florida scrub and sandhill vegetation on high sand ridges in south-central Florida.