Acanthomyrmex crassispinus

Little is known about the biology of .

Identification
Wheeler (1930) - This species is clearly different, especially in the character of the thoracic spines and petiolar node from any of the five previously described species of the rare and interesting lndomalayan genus Acanthomyrmex, namely Acanthomyrmex ferox of Perak and Sumatra, Acanthomyrmex luciolae of Ceylon, Acanthomyrmex notabilis from the island of Batchian, Acanthomyrmex dyak and Acanthomyrmex dusun from Borneo. It will he noticed that, with the exception of ferox, all of these species are known only from islands. The peculiar soldier form of Acanthomyrmex closely resembles that of Pheidole, hut the enormous head projects backward over the thorax, which lacks the long pronotal spines of the worker.

Moffett (1986) - Both castes with each scape having a small lateral flange proximad; propodeal spines wide and blade-like in profile; pilosity very sparse; from Taiwan.

Distribution based on Regional Taxon Lists
Oriental Region: Taiwan.

Nomenclature

 * . Acanthomyrmex crassispina Wheeler, W.M. 1930a: 101, fig. 2 (w.) TAIWAN.
 * Type-material: 5 syntype minor workers.
 * Type-locality: Taiwan (“Formosa”): Botel Tobago (= Lanyu I.), vi.1926, no. 49 (R. Takahashi).
 * Type-depositories: MCZC, USNM.
 * Moffett, 1986c: 69 (s.).
 * Status as species: Chapman & Capco, 1951: 114; Moffett, 1986c: 69 (redescription); Bolton, 1995b: 53; Lin & Wu, 1998: 86 (redescription); Lin & Wu, 2003: 64; Terayama, 2009: 187; Yamada, Ito, et al. 2018: 10.
 * Distribution: Taiwan.

Worker
Length 3-3.5 mm.

Head subrectangular, distinctly broader than long, with straight, subparallel cheeks, pronounced anterior angles, broadly excised posterior border and somewhat rounded posterior corners. Eyes small, convex, hemispherical, at the middle of the sides of the head. Mandibles large, broad and convex, with the external borders straight in the middle, the terminal borders long and toothless, except for four or five rather indistinct apical denticles, the basal border concave in the middle but forming a right angle with the terminal border. Clypeus very short and transverse, with feebly and broadly concave anterior border, the upper surface with two median carinae, each terminating in a minute denticle at the anterior border. Frontal carinae widely separated and widely diverging posteriorly, forming the mesial borders of distinct scrobes for the basal two thirds of the scapes. Frontal area distinct, triangular. Antennae rather stout; scapes extending about one fourth their length beyond the posterior corners of the head; distinctly flattened, somewhat expanded and angulate basally, with a ridge on the outer side as far back as the middle of their length; first funicular joint nearly twice as long as broad, joints two to eight slightly longer than broad, the terminal joint as long as the two preceding subequal joints of the club. Thorax of the usual structure, but the two pairs of spines, one on the pronotum and one on the epinotum, as long as the height of the thorax, the former pair being somewhat shorter than the latter. Both pairs are stout, though the epinotal pair is more so, straight, directed upward a:o.d outward and only very slightly bent backward at their tips, which taper rather rapidly and are not very acute. The epinotal spines are flattened and their anterior borders are distinctly ridged. Metasternal angles acutely dentate. Petiolar peduncle as long as the remainder of the segment, the node cuneate in profile and acute above, its superior border rather deeply and angularly excised so that it forms two triangular teeth which are as long as broad at their bases. Postpetiole cuboidal; seen from above rectangular, slightly broader than the petiole, slightly longer than broad and distinctly broader behind than in front, with straight sides, its node in profile with flat dorsal and perpendicularly truncated anterior and posterior surfaces. Gaster broadly elliptical, convex above and below, with rather straight anterior border. Legs stout, the tibiae clavate, the femora thickened in the middle.

Shining; mandibles, legs and gaster more so than the remainder of the body. Mandibles smooth, very finely and obscurely coriaceous. Clypeus smooth in the middle between the carinae, coarsely rugose on the sides. Head covered with circular foveolae separated by coarse rugae which are regularly reticulate on the front and occiput but irregularly longitudinal on the cheeks. Antennal scrobes transversely rugulose. Pro- and mesonotum sculptured like the posterior portion of the head; mesopleurae with a few very coarse rugae, the short base of the epinotum with several finer longitudinal rugae, the declivity, spines and petiole smooth; postpetiole smooth above, coarsely reticulate-rugose on the sides; gaster, legs and scapes smooth and polished.

Hairs yellowish, very delicate, short, blunt, sparse and erect, confined to the head, thorax and scapes; clypeus and tip of gaster with a few longer, pointed hairs.

Head, thorax and funiculi ferruginous red; mandibles, scapes, thoracic spines, pedicel, gaster and legs brownish yellow; terminal borders of mandibles black.

Moffett (1986) - Minor. Syntypes measuring HW 1.07 to 1.09, HL 0.87 to 0.90 (CI 121 to 123), ML 0.75 to 0.78 (MI 86 to 89), SL 0.97 to 0.98 (SI 90 to 91), EL 0.16 to 0.17, HFL 1.08 to 1.10 (FLI 122 to 125; FWI 23 to 24) mm. Head concave across posterior margin in full-face view, although not as strongly as in Acanthomyrmex luciolae. Head widest above eyes. Head with rounded, thick-walled foveae, and dorsally with very few, scattered hairs (these standing 0.08 to 0.10 mm). Scapes virtually smooth, not feebly rugose as in most Acanthomyrmex. Scapes also with a distinctive lateral flange extending longitudinally at their bases. Clypeal index 128-131. Lobe to each side of medial clypeal hair very feeble, and relatively widely separated from the hair; lateral clypeal hairs not in a completely enclosed fovea. A well-developed rugum extends back from each of the medial clypeal lobes, separating a smooth medial clypeal region from the more lateral areas. Mandibles lacking a ventral tooth.

Spines on trunk slightly curved caudad; propodeal spines somewhat longer than those on pronotum, and also slightly compressed laterally so as to appear wide and blade-like in profile. Pronotal spines lacking conspicuous hairs. Pronotal angle not forming a feeble tooth. Sculpture on trunk (particularly on dorsum) relatively feebly impressed. Propodeal declivity bordered on each side by a single rugum extending from the base of each propodeal spine.

Node of petiole as in figure, PWI intermediate (88 to 92); node lacking the single pair of hairs found low on caudal face of petiolar node of other Acanthomyrmex species. Anterior peduncle of petiole relatively short and deep, lacking lateral and sublateral hairs; subpetiolar declivity present. Postpetiole subrectangular, almost as long as it is wide in dorsal view, and with two or three conspicuous rugae on each side; lacking pilosity. Caster virtually without pilosity. Femora lacking all but basal hairs, and with ventral surfaces flattened or only very feebly concave. Head and trunk orange yellow, with legs yellow.

Major. Individual from Botel Tobago (Lanyu Island, Taiwan) measures HW 1.99, HL 2.11 (CI 94), SL 1.03 (SI 52), EL 0.25, HFL 1.32 (FLI 62; FWI 19) mm. As in the minor, head, trunk, and gaster with very little long pilosity. Head as wide below eyes near mandible bases as above eyes (greatest HW is above eyes in other species). Shallow oval foveae scattered over head surface, not as dense as in other luciolae group species; foveae most numerous laterally and on vertex. Cephalic hollow well-developed, with medial sulcus extending below it to the frontal area shallow and inconspicuous. Darkly pigmented medial streak very short, present between lobes on vertex but not extending to cephalic hollow. Forward margin of clypeus lacking a medial projection, although two low, rounded lobes are present. Propodeal spines moderately long, curved caudad; compressed as in the minor worker. Scape with lateral flange near base. PWI value 100.

Type Material
Described from five specimens from Botel Tobago.

Moffett (1986) - Taiwan: Botel Tobago (=Lanyu Island), 6/1926, no. 49, three minor workers R. Takahashi, and U.S. National Museum [examined].

References based on Global Ant Biodiversity Informatics

 * Chapman, J. W., and Capco, S. R. 1951. Check list of the ants (Hymenoptera: Formicidae) of Asia. Monogr. Inst. Sci. Technol. Manila 1: 1-327
 * Guénard B., and R. R. Dunn. 2012. A checklist of the ants of China. Zootaxa 3558: 1-77.
 * Hu C.-H. 2006. Indigenized conservation and biodiversity maintenance on Orchid Island. PhD Thesis, graduate school of the University of Minnesota. 150 pages.
 * Li Z.h. 2006. List of Chinese Insects. Volume 4. Sun Yat-sen University Press
 * Lin C. C., and W. J. Wu. 1998. The ant tribe Myrmecinini (Hymenoptera: Formicidae) of Taiwan. Chinese Journal of Entomology 18: 83-100.
 * Moffett, M. 1986. Revision of the myrmicinae genus Acanthomyrmex (Hymenoptera: Formicidae). Bulletin of the Museum of Comparative Zoology 151(2):55-89.
 * Moffett, M. W. 1986. Revision of the myrmicine genus Acanthomyrmex (Hymenoptera: Formicidae). Bulletin of the Museum of Comparative Zoology 151:55-89.
 * Terayama M. 2009. A synopsis of the family Formicidae of Taiwan (Insecta: Hymenoptera). Research Bulletin of Kanto Gakuen University. Liberal Arts 17:81-266.
 * Terayama Mamoru. 2009. A synopsis of the family Formicidae of Taiwan (Insecta, Hymenoptera). The Research Bulletin of Kanto Gakuen University 17: 81-266.
 * Terayama, M. 2009. A synopsis of the family Formicidae of Taiwan (Insecta; Hymenoptera). The Research Bulletin of Kanto Gakuen University 17: 81-266.
 * Wheeler W. M. 1930. Formosan ants collected by Dr. R. Takahashi. Proceedings of the New England Zoological Club 11: 93-106.