Leptanilloides chihuahuaensis

The specimens of L. chihuahuaensis were collected in Townes style Malaise traps (Townes 1972) at two locations within Davis Mountains State Park. The first location was on the south (north-facing) slope of Keesey Canyon adjacent to a hillside drainage area. The vegetation at this site was dominated by short grasses but also included scattered forbs and a few low trees and shrubs. The noncalcareous soil, of igneous origin, was shallow, well drained, and extremely rocky (Turner 1977). The second location was in Limpia Canyon on the dry floodplain of the intermittent Limpia Creek. The soils here were similar to the first site, but the vegetation differed in having taller grasses and forbs, with grasses being less dominant, and with forbs, shrubs, and small trees being more numerous. Many rocky, unvegetated areas were also scattered through this habitat. The Malaise trap at this site was located only 20 m from the north (south-facing) slope of Limpia Canyon, which had similar habitat to the first site, so it is possible that the ants in this trap originated from the canyon slope rather than the floodplain. (MacGown 2015)

Identification
MacGown et al. (2015) - Male Of the six males that have been described in the Leptanilloides genus-group, L. chihuahuaensis is most similar to “Leptanilloidinae male 1” from southern Mexico described by Borowiec & Longino (2011). Leptanilloides chihuahuaensis differs from “Leptanilloidinae male 1” by having finer and sparser pilosity, in dorsal view the petiole being widened anteriorly and posteriorly, parameres being narrower and incurved, and the hindwing having three hamuli (instead of two). Males of L. chihuahuaensis differ from males of Leptanilloides golbachi by lacking submarginal cells and a stigma in the forewing, possessing a free M vein, and having a larger paramere (about as long as petiole); from Leptanilloides mckennae by lacking submarginal cells and a stigma in forewing and having a much shorter paramere (in side view) (Ward 2007); from Leptanilloides nubecula by being light to medium brown instead of dark brownish-black and being much smaller (HL 0.22–0.24 in L. chihuahuaensis vs. HL 0.32 in L. nubecula), and from both “Leptanilloidinae male 2 and male 3” (Borowiec & Longino 2011) by the much smaller size (HL 0.22–0.24 vs. HL 0.30–0.33 of “Leptanilloidinae male 2 and male 3”) and by lacking submarginal cells and stigma in the forewing. Five other male morphotypes unassociated with workers were briefly discussed by Ward & Brady (2009). Leptanilloides chihuahuaensis differs from each of these by lacking submarginal cells and a stigma in the forewing. Geographically, L. chihuahuaensis is the only species thus far know to occur in the United States.

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

Castes
Known from males only.

Nomenclature

 *  chihuahuaensis. Leptanilloides chihuahuaensis MacGown, Schiefer & Branstetter, 2015: 394 (m.) USA.

Despite the fact that males of all species in the Leptanilloides genus-group have not been described and that males collected in Texas were unassociated with a colony, we believe there is sufficient evidence for describing L. chihuahuaensis as a new species. First, L. chihuahuaensis has a very disjunct distribution and occurs in a markedly different habitat than other species. Second, there are obvious morphological features that distinguish L. chihuahuaensis from other described males. And lastly, COI sequence divergence, as compared to several other species with data in GenBank, including L. gracilis, exceeds 8%. Although we do not think that this divergence level by itself is sufficient for species status - it has been shown that intraspecific divergence can be quite high (e.g. Meyer and Paulay 2005, Wiemers and Fiedler 2007) – we do believe that the result strengthens our argument.

Male
Holotype: HW 0.24, HL 0.24, EL 0.11, MDL 0.13, SL 0.08, PedL 0.06, FlaLI 0.04, FlaLII 0.04, FlaLXI 0.12, MH 0.29, ML 0.46, PrW 0.20, PW 0.09, PL 0.07, AIIIW 0.14, AIIIL 0.07, AIVW 0.20, AIVL 0.09, FFeW 0.05, FFeL 0.23, HFeL 0.24, HTiL 0.26, FWL 1.46, CI 100, MI 63, PI 128.

HW 0.24, HL 0.22, EL 0.09–0.11, MDL 0.13, SL 0.09, PedL 0.06–0.07, FlaLI 0.04, FlaLII 0.04, FlaLXI 0.11–0.12, MH 0.30–0.31, ML 0.45–0.46, PrW 0.18, PW 0.07–0.08, PL 0.06–0.07, AIIIW 0.15, AIIIL 0.07–0.10, AIVW 0.18–0.19, AIVL 00.10, FFeW 0.05, FFeL 0.21, HFeL 0.23, HTiL 0.26, FWL 1.38, CI 109, MI 65–69, PI 114–117.

Body size minute. Color light yellowish-brown, head and margins of abdominal segments IV–VII darker, appendages (antennae, mandibles, legs) lighter. Integument mostly smooth and shiny, with simple curved to strongly curved suberect to decumbent setae; pilosity on head, mesosoma, petiole, and first gastral tergite (AIII) scattered and not obscuring the shininess of the integument; pilosity denser on remainder of gaster and appendages. Head in full-face view excluding eyes about as long as wide, widest above eyes; posterior corners of head evenly rounded. Eyes large, bulging, occupying almost half the side of head. Ocelli small, protruding slightly, arranged in almost an equilateral triangle, but with distance between lateral ocelli slightly greater than distance between lateral ocellus and median ocellus; distance between median ocellus and eye approximately the length of eye. Clypeus short, tranverse, lacking lamelli; lateroclypeal teeth and hypostomal teeth lacking. Mandible slender, falcate; apex  blunt;  masticatory  margin  edentate;  external  margin  of  mandible  mostly  evenly  curved  along  its  length; mandible tips overlap at closure.

Antennal sockets circular and exposed, located at the anterior clypeal margin with anterior edge of sockets slightly overlapping anterior clypeal margin. Antenna 13-merous; scape, pedicel, and each flagellomere longer than wide. Scape length about twice the length of the first flagellomere, and about the combined length of the first and second flagellomere; scape subequal to the length of ultimate flagellomere; pedicel thickened, length about 1.5 times width; flagellomeres 1-11 each at least twice as long as wide; first and second flagellomeres subequal in length.

Pronotum U-shaped in dorsal view, reduced anteromedially to a thin horizontal strip, set below the level of the dorsally protruding mesonotum; pronotum triangular in lateral view, with pointed posterior apex directed toward wing base. Mesoscutum lacking notauli; parapsidal lines not discernable. Axillae depressed, not meeting medially connected by a narrow furrow. Tegula, or tegula-like structure present at wing base, minute, inconspicuous, with 2-3 erect setae. Mesopleuron lacking oblique transverse sulcus, not divided into anepisternum and katepisternum. Mesoscutellum prominently bulging, as seen in lateral view. Metapleural gland not discernable. Propodeum with dorsal and  declivious  surfaces  not  differentiated,  evenly  rounded. Propodeal spiracle  small,  ovate,  positioned  slightly  below  midheight  of  propodeum  and  slightly  posterior  to  the  midlength. Legs slender,  mesotibia  and  metatibia each with two simple spurs, pretarsal claw lacking preapical tooth.

Wings with  reduced  venation;  clear;  fringed  with  short  to  longer  fine  setae;  with  numerous  short,  fine  microsetae evenly distributed across wing surfaces and with scattered longer setae present. Fore wing: Costal (C) vein present,  about  1/2  the  length  of  wing,  tubular  basally  for  less  than 1/4 the  length  of  wing,  then  becoming  nebulous before fading out completely. Pterostigma not present. Subcostal and radial veins fused forming Sc+R; located just below and parallel to costal vein, approximately the same length as costal vein and similarly tubular for about 1/2 of its length before becoming nebulous. Medial (M) and cubital (Cu) veins fused (M+Cu), nebulous, slightly less than 1/4 of the wing length. Anal (A) vein present beneath M+Cu, about the same length as M+Cu, tubular for slightly more than half of its length before becoming nebulous; apically M+Cu connected to A by nebulous crossvein cu-a; subbasal cell present between M+Cu and A. Branching upward from the top of Cu-a is the tubular abscissa Rs+M (the joined veins M·f1 and Rs+M). Radial sector (Rs), tubular, branches upward from Rs+M, then becomes nebulous just past the nebulous/spectral crossvein 2r-rs (1r-rs is absent). M branches off of Rs+M just before Rs, appearing spectral basally then continuing as a nebulous vein that does not reach the wing margin. Cu is present as a nebulous vein that branches off near the apex of A; Cu does not reach the wing margin. Posterior margin of fore wing with narrow, conspicuous fold where hamuli attach.

Hind wing with Sc+R present, tubular basally before becoming nebulous, less than ¼ the length of wing. No other veins present. Anterior margin of hind wing past midlength with a thin, but conspicuous dark stigma. Three hamuli present in the region of the stigma. Jugal lobe absent.

Petiole (abdominal segment II) subquadrate in lateral view, about as long as high or wide, not constricted posteriorly; in dorsal view anterior corners widened, sides slightly constricted, appearing shallowly concave before widening posteriorly; petiole broadly joined to abdominal segment III; petiolar spiracle located on anterior third of the segment, near anterodorsal extremity. Abdominal segment III larger than petiole, not developed as postpetiole, and not separated from abdominal segment IV by a constriction. Abdominal spiracles III, IV, V, and VI located on anterior third  of  tergites  (abdominal  spiracle  VII  not  visible  in  examined  specimens). Abdominal tergite  VIII (pygidium) small, simple and visible dorsally, not entirely covered by abdominal tergite VII. Pygostyli absent. Abdominal sternite IX (subgenital plate) with posterior margin broadly concave, but with a median subtriangular process. Paramere (basimere + telomere) small (about the length of petiole); basimere roughly triangular, widest at base, narrowing  to  incurved  falcate  telomere  that  terminates  in  a  blunt  apex. Volsella triangular,  with  slightly  rounded apex; volsella not differentiated into digitus and cuspis. Penisvalva elongate triangular, extending to about as far as paramere apex.

Type Material
Holotype male: [United States] TEXAS, Jeff Davis Co., Davis Mts. St. Pk., 5118', 30°35'27"N 103°56'26"W, 22– 25 July 2014, T.L. Schiefer, Malaise trap on hillside on highland grassland, W.H. Cross Expedition. [Holotype deposited in Harvard Museum of Comparative Zoology, Cambridge, MA]. Specimen code MEM 207971. Paratype males: Two point-mounted specimens with the same data as the holotype but with unique specimen code: MEM 207972 and MEM 207973 (both specimens in ; and three specimens, one point-mounted and two in 95% ethanol, with the following collection data: [United States] TEXAS, Jeff Davis Co., Davis Mts. St. Pk., 4915', 30°36'08"N 103°54'55"W, 21–25 July 2014, T.L. Schiefer, Malaise trap in riparian area in desert scrub/grassland, W.H. Cross Expedition with unique specimen codes: MEM 207974 [point mounted specimen deposited in MEM], MEM 207975 [preserved in 95% ethanol for DNA study, deposited in MEM] and MEM 207976 [preserved in 95% ethanol for DNA study, deposited in MEM].

Etymology
Named for the Chihuahuan Desert region where specimens were collected.

References based on Global Ant Biodiversity Informatics

 * MacGown J. A., T. L. Schiefer, and M. G. Branstetter. 2015. First record of the genus Leptanilloides (Hymenoptera: Formicidae: Dorylinae) from the United States. Zootaxa 4006 (2): 392–400.