Leptanilloides chihuahuaensis

Macgown, Joe A., Schiefer, Terence L. & Branstetter, Michael G., 2015, First record of the genus Leptanilloides (Hymenoptera: Formicidae: Dorylinae) from the United States, Zootaxa 4006 (2), pp. 392-400 : 394-398

Leptanilloides chihuahuaensis

( Figs. 1 , 2 )

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 (MCZC), 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 Mississippi Entomological Museum (MEM), Mississippi State, MS, USA]; 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].

Holotype measurements and indices: 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.

Additional paratype measurements and indices (two males): 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 0 0.10, FFeW 0.05, FFeL 0.21, HFeL 0.23, HTiL 0.26, FWL 1.38, CI 109, MI 65–69, PI 114–117.

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

Diagnosis (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 Amyrmex golbachi Kusnezov, 1953 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 L. mckennae Longino 2003 by lacking submarginal cells and a stigma in forewing and having a much shorter paramere (in side view) (Ward 2007); from L. nubecula Donaso, Vieira & Wild, 2006 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.

Description (male): 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 ½ the length of wing, tubular basally for less than ¼ 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 ½ of its length before becoming nebulous. Medial (M) and cubital (Cu) veins fused (M+Cu), nebulous, slightly less than ¼ 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.

Analysis of COI. A 658 bp region of the mitochondrial gene COI, the barcode region, was sequenced successfully and the resulting consensus sequence was submitted to GenBank ( Table 1 ). Five additional COI sequences for Leptanilloides were found and downloaded from the BOLD database ( Table 1 ), including three for L.

gracilis Borowiec & Longino (southern Mexico, Honduras), one for L. nubecula Donoso et al. (Ecuador) , and one for an undescribed species L. MAS001 (Costa Rica). Comparing L. chihuahuaensis to the other specimens, pairwise genetic distances were all above 8.0%, ranging from 8.2% ( L. gracilis , Honduras) to 20.1% ( L. nubecula , Ecuador).

Figures

FIGURE 1. Leptanilloides chihuahuaensis, male, holotype (MEM 207971): (A) head in full-face view, (B) petiole in dorsal view, (C) tergite VIII and exposed male genitalia in dorsal view, (D) sternite IX and exposed male genitalia in ventral view, (E) lateral habitus, and (F) dorsal habitus. Abbreviations: ASIX = ninth abdominal sternite, ATVIII = eighth abdominal tergite, Ax = axilla, Msp = mesopleuron, MsScl = mesoscutellum, MsSct = mesoscutum, Mtn = metanotum, P = petiole, Ped = Pedicel, Pm = paramere, Prnt = pronotum, Prpd = propodeum, Pv = Penivalva, Sc = Scape, and Vol = volsella.

FIGURE 2. Leptanilloides chihuahuaensis, male, holotype (MEM 207971): (A) lateral habitus and (B) forewing and hindwing showing labeled veins. Abbreviations: 2 r-rs = second radial sector cross-vein, A = anal vein, C = costal vein, Cu = cubital vein, cu-a = cubital-anal cross-vein, ha = hamuli, M = medial vein, M + Cu = merged medial-cubital veins, Rs + M = merged medial and radial sector plus medial veins, Rs = radial sector, Sc + R = merged subcostal and radial veins.

Tables

TABLE 1. Information for six Leptanilloides specimens that have available COI sequence data: species name, country of origin, GenBank and BOLD accession numbers, length of COI sequence fragment, and uncorrected (p) distance as compared to L. chihuahuaensis.

Species	Country	GenBank#	BOLD#	COI Size (bp)	p-distance (%)
Leptanilloides chihuahuaensis	USA (Texas)	KT007966	n/a	658	-
L. gracilis	Mexico (Chiapas)	n/a	ASLAM1070-11	282	10.1
L. gracilis	Honduras	n/a	ASLAM1144-11	658	10.3
L. gracilis	Honduras	JF863464	ASLAM381-11	525	8.2
L. nubecula	Ecuador	DQ353302	GBAH2069-06	844	20.1
L. MAS001	Costa Rica	KF371235	ACGAG099-11	503	10.6