Acanthomyrmex glabfemoralis

An opportunistic cavity nesting species that includes seeds in its diet, some of which are stored in their nest.

Distribution based on Regional Taxon Lists
Oriental Region: Vietnam. Palaearctic Region: China.

Biology
Eguchi, Bui and Yamane (2008) - This species nests in cavities of rotting twigs, wood fragments and logs, in cracks and cavities of stones, and under stones on the forest floor. Although many small seeds are usually stored in nest chambers (e.g., Eg03-VN-055, -205, -223, -245; Eg04-VN-032; Eg26ix06-15), animal matter is also gathered (see Eguchi et al. 2004). Both the normal queen and the dwarf queen probably contribute to the reproduction (we did not confirm this by observing the condition of the ovaries and spermathecae of fresh material), but we have not yet found any colony which had both normal (dealate and/or alate) and dwarf queens. Geographical variation of colony structure was also observed. All of the colonies which we found in West Yen Tu N. P. (excluding colony B&E03-46 with a dwarf queen instead of a normal queen), Chua Yen Tu, Ky Thuong, Cuc Phuong and Pu Mat colonies had a single dealate queen (or queenless probably due to sampling errors), on the other hand those in Van Ban had a single or multiple dwarf queen (or were queenless). Circumstantial evidences suggest a possibility that A. glabfemoralis remains in a transitional stage toward the reproduction system in which the colony foundation and growth are exclusively done by ergatoid(s) (as seen in Acanthomyrmex minus, Acanthomyrmex padanensis and Acanthomyrmex sulawesiensis and Acanthomyrmex humilis). A few cases of geographical variation in colony composition have been known in other ants. For instance, Dalecky et al. (2005) comprehensively studied polygyny in the plant-ant Petalomyrmex phylax and concluded that the latitudinal cline in monogyny/polygyny may have resulted from historical processes such as selection for a more dispersive strategy along a colonization front (i.e., monogyny may have been favored along the front of the southward expansion of P. phylax). Although Gnamptogenys bicolor adopts worker reproduction in most of its geographical range, we found colonies with alate queens in North Vietnam, the northern border of its range (K. Eguchi and T.V. Bui, unpubl.). Vietnam provides good material for understanding evolution of ergatoid and worker reproduction and mechanisms maintaining geographical variation in colony composite on (fresh colonies of Acanthomyrmex glabfemoralis as well as Gnamptogenys bicolor are easily obtained in some areas of North Vietnam).

Colonies of A. glabfemoralis contain a single dealate normal queen, or instead contain single or multiple dwarf queens, while colonies of Acanthomyrmex humilis contain ergatoids only (Eguchi et al. 2008), Acanthomyrmex glabfemoralis and A. humilis gather seeds (Eguchi et al. 2004, Eguchi pers. observ.).

Worker
Minor

Nomenclature

 *  glabfemoralis. Acanthomyrmex glabfemoralis Zhou & Zheng, 1997a: 47, figs. 1, 2 (w.) CHINA. Eguchi, Bui & Yamane, 2008: 232 (s.q. dwarf q. m.).

Worker
Eguchi, Bui and Yamane (2008) - Major (5 nontypes). HL 2.60-3.00 mm; HW 2.25-2.56 mm; SL 1.10-1.28 mm; HFL 1.33-1.40 mm; CI 84-88; SI 48-50; HFI 55-59.

Minor (5 nontypes). HL 0.92-1.08 mm; HW 1.04-1.18 mm; SL 0.95-1.10 mm; HFL 0.99-1.19 mm; CI 108-113; SI 92-97; FI 96-102.

Major. Body reddish brown to dark reddish brown; legs and often antennae and apical part of gaster paler. Body sculpture basically as in Figs. 1-3, but with a certain amount of variation. Head in full-face view at least with weak posteromedian emargination; dorsal and lateral faces of cranium at most with a few standing hairs; frontal lobe poorly developed, only partly concealing antennal socket; frontal carina conspicuous; antennal scrobe deep and conspicuous, posteriorly bent anteroventrad to form a “funicular scrobe” above compound eye; median part of clypeus produced anteriad, with weak to inconspicuous emargination at middle of anterior margin, usually lacking a median seta and lateral setae (or rarely having a thin and short median seta); antenna 12-segmented with 3-segmented club; shaft of antennal scape when laid backward not extending beyond midlength of head; leading edge of the shaft forming a low longitudinal lobe a little apically to encircling basal flange; outer surface of mandible smooth (sparsely with tiny punctures which usually bear very short appressed hairs); masticatory margin of mandible almost edentate (teeth having been worn down to nothing, but apical and preapical teeth often inconspicuously present). Mesosoma shortened and stout; its dorsum with a few standing hairs; promesonotal suture present as a weak groove dorsally; pronotal spine absent; metanotal groove present as inconspicuous broad impression just anteriorly to base of propodeal spine; the groove sometimes bordered anteriorly with low ridge; metapleural lobe well developed, angularly projecting posterodorsad; propodeal spine in lateral view relatively broad basally and weakly down-curved or slightly sinuate, without standing hairs but with a few very short decumbent to appressed hairs. Dorsum of each femur without standing hairs. Petiole in lateral view with long anterior pedicel; petiolar node in lateral view moderately raised, with relatively acute apex, in posterior view with concavity between acute lateral angles or short and stout spines (rarely angles round as in the major of Eg18iii06-11); “post-nodal” face behind apex of petiolar node till articulation with postpetiole consisting of a steep slope followed by a very short horizontal face in lateral view; subpetiolar process present as a small dent; postpetiole in lateral view moderately raised dorsally, with blunt anteroventral angle, much shorter than high and (much) shorter than broad (excluding helcium). First gastral tergite at most with a few long hairs, but with many very short appressed hairs.

Minor (redescription mainly based on the Vietnamese material). Body reddish brown to dark reddish brown; mandibles, antennae, apical part of pronotal and propodeal spines, legs, apical part of gaster usually paler. Body sculpture as in Figs. 4-6. Head with standing hairs, in full-face view with its posterior margin broadly concave; frontal lobe poorly developed, only partly concealing antennal socket; frontal carina conspicuous; antennal scrobe shallow but conspicuous, posteriorly not bent anteroventrad; anterior clypeal margin with a conspicuous median seta, and usually with conspicuous lateral setae, in middle with four processes (two located between median and lateral setae, and the other two lateral to lateral setae); oblique-longitudinal ridge running backward from each process; eye in full-face view strongly convex, located a little behind midlength of head; antenna 12-segmented with 3-segmented club; the shaft of antennal scape when laid backward usually extending a little beyond posterolateral corner of head; leading edge of shaft forming a low longitudinal lobe a little apically to the encircling basal flange; masticatory margin of mandible with relatively small apical and preapical teeth followed by small denticles that are relatively broadly separated. Mesosoma in lateral view slenderer than that of the major; its dorsum sparsely with standing hairs; promesonotal dome in lateral view convex gently; promesonotal suture absent dorsally; pronotal spine slender, without standing hairs but with several very short decumbent to appressed hairs; metanotal groove almost absent; metapleural lobe well developed, angularly projecting posterodorsad; propodeal spine long, in lateral view slender and usually down-curved or sinuate in apical part, without standing hairs but with a few very short decumbent to appressed hairs. Dorsum of each femur without standing hairs. Petiole in lateral view with relatively long anterior pedicel; petiolar node in lateral view moderately to strongly raised, with relatively angulate apex, in posterior view with concavity between acute lateral angles or spines; "post-nodal" face behind apex of petiolar node till articulation with postpetiole consisting of a steep slope followed by a very short horizontal face in lateral view; subpetiolar process present as a small angle or dent; postpetiole in lateral view moderately raised dorsally, shorter than high and (a little) broader than long (excluding helcium). First gastral tergite without standing hairs, but with many very short appressed hairs.

Queen
Eguchi, Bui and Yamane (2008) - Normal queen (5 nontypes). HL 1.80-2.08 mm; HW 2.00-2.33 mm; SL 1.08-1.23 mm; MNH 1.60-1.95 mm; MSW 1.38-1.61 mm; HFL 1.40-1.56 mm; CI 108-112; SI 52-55; MNI 83-87; MSI 69-73; FI 67-71.

Dwarf queen type A (1 nontype). HL 2.14 mm; HW 2.24 mm; SL 1.18 mm; MNH 1.28 mm; MSW 1.08 mm; HFL 1.48 mm; CI 105; SI 53; MNI 84; MSI 48; FI 66.

Dwarf queen type B (3 nontypes). HL 1.68-1.73 mm; HW 1.76-1.83 mm; SL 1.06-1.11 mm; MNH 1.05-1.13 mm; MSW 0.81-0.86 mm; HFL 1.29-1.30 mm; CI 103-108; SI 58-62; MNI 73-80; MSI 44-48; FI 71-73.

Head and mesosoma reddish brown to dark reddish brown; antennae, legs and apical part of gaster usually paler. Body sculpture basically as in Figs. 7-9 (sculpture on head and mesoscutum weaker in queens from Pu Mat). Head in full-face view subrectangular, with lateral margins weakly diverging posteriad; posterior margin weakly concave medially; dorsum of cranium sparsely with standing hairs; frontal lobe poorly developed, only partly concealing antennal socket; frontal carina conspicuous, ending a little anteriorly to midlength between posterior margin of compound eye and posterior margin of head in lateral view; antennal scrobe deep and conspicuous, posteriorly bent anteroventrad to form an inconspicuous “funicular scrobe”; median part of clypeus produced anteriad, with weak emargination at middle of anterior margin, virtually lacking median and lateral setae; ocelli present; median ocellus in full-face view located a little behind level of posterior margin of compound eye; antenna 12-segmented with 3-segmented club; antennal scape when laid backward extending beyond midlength of head; masticatory margin of mandible almost edentate (teeth having been worn down to nothing, but apical and preapical teeth often remaining inconspicuously). Mesosoma short and high; its dorsum with standing hairs; pronotal spine absent; mesoscutellum in lateral view strongly raised dorsoposteriad (but relatively weakly raised in queens from Pu Mat), in dorsal view subtrapezoidal, very weakly concave posteromedially; metapleural lobe well developed, angularly projecting posterodorsad; propodeal spine in lateral view straight or down-curved, relatively broadly based, without standing hairs, but with a few very short appressed hairs. Venation of wings basically as in Fig. 10 (but in a queen of Eg01-VN-164 medio-cubital cross-vein located at or near base of radial sector + media). Dorsum of each femur usually without standing hairs. Petiole in lateral view with long anterior pedicel; petiolar node in lateral view relatively low but with relatively angulate apex, in posterior view with concavity between lateral angles or horns; “postnodal” face behind apex of petiolar node till articulation with postpetiole consisting of a steep slope followed by a very short horizontal face; subpetiolar process present as a small dent or angle; postpetiole in lateral view strongly raised dorsally, with anteroventral angle, much shorter than high and much shorter than broad (excluding helcium). First gastral tergite with several standing hairs among very short appressed hairs.

"Dwarf queen type A" (based on a single specimen collected in Yen Tu). Head and mesosoma reddish brown to dark reddish brown; antennae, legs and apical part of gaster paler. Body sculpture as in Figs. 11-13. Head as in the normal queen (see Figs. 7 and 8). Mesosoma, though having main sclerites as in Figs. 11 and 13, reduced in volume as compared to that of the normal queen (especially so concerning mesonotum); wings absent. Waist segments and gaster as in the normal queen.

"Dwarf queen type B" (based on specimens from colonies collected in Van Ban). Head and mesosoma reddish brown to dark reddish brown; antennae, legs and apical part of gaster paler. Body sculpture basically as in Figs. 14-16. Head basically as in the normal queen, but with the following distinct differences: dorsal and lateral faces of head covered with many standing hairs; sculpture more similar to the minor worker than to the normal queen; median part of clypeus often with a median and/or lateral seta(e); median ocellus often located in front of level of posterior margins of compound eyes. Mesosoma, though having main sclerites as in Figs. 14 and 16, reduced in volume as compared to that of the normal queen (especially so concerning mesonotum); wings absent. Waist segments and gaster basically as in the normal queen, but with denser standing hairs (Figs. 14 and 16).

Male
Eguchi, Bui and Yamane (2008) - Male (3 nontypes). HL 0.71-0.80 mm; HW 0.93-1.15 mm; SL 0.17-0.22 mm; MNH 0.88-1.09 mm; MSW 0.88-0.93 mm; HFL 0.99-1.13 mm; CI 130-144; SI 18-19; MNI 83-100; MSI 80-95; FI 98-108.

Body black, but apical part of antennae, legs and gaster dark yellow. Sculpture and pilosity on body as in Figs. 17, 18 and 20. Head in full-face view broadened subpentagonal, in profile strongly raised in anterior part of vertex (or moderately raised in males from Pu Mat), with posterolateral part very weakly produced posteriad (but not produced in males from Pu Mat); anterolateral part of head in which compound eye is located well produced laterally; frontal lobe, frontal carina and antennal scrobe absent; median part of clypeus produced anteriad, with truncated anterior margin, with a conspicuous median and rather thin lateral setae; ocelli present, with diameter less than distance between them; median ocellus in full-face view located a little behind level of posterior margins of compound eyes; antenna 13-segmented without club; antennal scape very short; when laid backward its apex located far anteriorly to median ocellus; antennal segment II very short; III much longer than broad, longer than IV-XII, and almost as long as XIII (but shorter than XIII in males from Pu Mat), somewhat flattened (Fig. 19); IV-XIII much longer than broad; IV very weakly flattened and weakly bent, or almost cylindrical; masticatory margin of mandible with relatively large apical tooth followed by several distinct teeth. Mesosoma short and high; pronotal spine absent; mesoscutellum in lateral view strongly raised dorsoposteriad, in dorsal view straight or hardly concave posteriorly; metapleural lobe well developed, projecting posterodorsad; posterolateral part of propodeal dorsum in profile forming a triangular process or at least a blunt angle; propodeal spiracle directed backward; venation of wings as in Fig. 21. Petiole in lateral view with long anterior pedicel; petiolar node in lateral view very low and roundly raised, in posterior view straight or hardly concave dorsally (but roundly convex in males from Pu Mat); “post-nodal” face behind apex of petiolar node till articulation with postpetiole long and very gently sloping in lateral view; subpetiolar process absent or vestigial; postpetiole in lateral view very weakly raised dorsad (moderately raised in males from Pu Mat N. P.), without anteroventral angle, almost as long as or a little shorter than high, and a little shorter to a little longer than broad (excluding helcium).

Type Material
Eguchi, Bui and Yamane (2008) - Holotype (minor): China: Guangxi: Huaping Natural Conservation, 8.VII.1995, leg. Shanyi Zhou. We were unable to borrow the type material, but we examined two majors and two minors [Da Yao Shan N. R., Guangxi, China, 18.IX.1998, leg. S. Zhou] determined as A. glabfemoralis by S. Zhou who is the first author of the original description of the species.