Strumigenys rostrataeformis

This species was described from Magi, Kochi Prefecture, Japan, and the northernmost distribution record is from Kinkazan, Miyagi Prefecture (Sonobe, 1977). Okamoto (1952) found S. rostrataeformis in a decaying tree trunk while Brown (1949) reported a collection from a decayed stump.

Identification
Bolton (2000) - A member of the Strumigenys rostrata-group. The two Japanese species of this group described by Brown, Strumigenys incerta and rostrataeformis, are closely related but may be separated by the following characters.

S. rostrataeformis: Anterior clypeal margin transverse between the points where the outer margins of the fully closed mandibles intersect the clypeal margin. Pronotal humeral hair stout and remiform. Longest pair of standing hairs on mesonotum remiform. First gastral tergite with apical and basal transverse rows of standing hairs, no hairs between these rows. Standing hairs behind highest point of vertex not distinctly narrower or finer than those on the frons. Spongiform lobe on side of petiole in dorsal view at least half the width of the disc of the node.

S. incerta: Anterior clypeal margin broadly concave between the points where the outer margins of the fully closed mandibles intersect the clypeal margin. Pronotal humeral hair fine and flagellate. Longest pair of standing hairs on mesonotum simple but blunted apically. First gastral tergite with standing hairs between the apical and basal rows. Standing hairs behind highest point of vertex curved, simple, contrasting with the more spatulate hairs on the frons. Spongiform lobe on side of petiole in dorsal view much less than half the width of the disc of the node.

Japanese Ant Image Database: This species is similar to Strumigenys incerta. The shape of the anterior margin of the clypeus, which is often cited as a distinguishing character, can be difficult to interpret, but the presence of a pair of scale-like hairs on the pronotal humeri enables reliable recognition of S. rostrataeformis.

Distribution based on Regional Taxon Lists
Palaearctic Region: Japan.

Nomenclature

 *  rostrataeformis. Smithistruma rostrataeformis Brown, 1949d: 12 (w.) JAPAN. Combination in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 127. See also: Bolton, 2000: 460.

Worker
Holotype. TL 2.35 mm., HL 0.61 mm., WL 0.60 mm., CI 67, MI 14-15. Scape L 0.32 mm.; Funicuius L 0.45 mm., funicular segment V (apical) 1 ¼ times as long as the four basal segments taken together.

This form quite definitely belongs to the Strumigenys rostrata group; furthermore, it has quite a striking resemblance to rostrata itself, hence the name. In many characters, the new species is intermediate between Strumigenys incerta and rostrata; the comparison below is made chiefly against incerta, and where comparison is made to rostrata, that species is always mentioned by name.

(1) The head is slightly more depressed dorsally than in incerta, nearly straight in lateral profile from vertex anteriorly, with the depression of the frontal area and concomitant elevation of the posterior clypeal border less marked (head intermediate to that of rostrata in these respects).

(2) Clypeus broader (1.3-1.4 times as broad as long\ more nearly plane; tumulus weakly shining and touching the anterior clypeal margin ; central portion of transverse anterior clypeal margin straight, not at all emarginate.

(3) Mandibles slightly longer than those of incerta, but not nearly so long as those of rostrata; dentition appearing similar to that of both species at full closure.

(4) Pilosity white and conspicuous, differing in detail from that of incerta and rostrata. Hairs on disc of clypeus short, erect or suberect and strongly clavate. Five large spatulate hairs fringing each side of the free clypeal margin, those nearest the anterior margin (on the “anterior corners”) are largest, but not nearly so long relative to the rest as in rostrata; slightly longer than the corresponding ones of incerta, curved anteriorly and medially. Straight transverse section (anterior border) of free clypeal margin with about three small, indistinct incurved spatulate hairs on each side of the middle, becoming shorter from the sides toward the middle. Anterior border of scape with about 7 prominent hairs, the largest one (at the blunt angle near the base) as long as the greatest scape width and with its tip broader than the rest of the hairs, which are narrowly spatulate apically. Remainder of cephalic dorsum with short inverted-spoon-shaped hairs, their broadened parts bent anteriorly more or less parallel to the integumental surface; those on the occiput a little longer, narrower and less strongly bent, but never nearly so long, erect and slender as those of incerta. Alitrunk with a pair of long, stiff flattened-clavate hairs on the humeral angles (these flagellate in incerta) and another pair of the same arising from low tubercles at the posterolateral pronotal angles. In addition, the promesonotum supports a very few small, indistinct appressed to suberect spatulate hairs. Petiole and postpetiole each with a few posteriorly inclined clavate hairs of varying lengths; a row of 5 or 6 long anteriody inclined weakly clavate hairs across the anterior of gastric tergite I and an erect pair of the same near the posterior border of that tergite; a few fine straight erect hairs about the gastric apex.

(5) Alitrunk a little more strongly depressed than in incerta, less so than in rostrata, the anterior pronotal surface more gently sloping than in incerta and only very gently convex antero-posteriorly. Pronotum sharply and arcuately marginate anteriorly, a feeble carina along the dorsolateral margins on each side causing a weak submarginate appearance. Mesonotum barely perceptibly marked off from the pronotum by an indistinct arcuate sutural line or ridge; posterior mesonotum very weakly depressed. Postmesonotal suture weakly depressed; median longitudinal carina fine but distinct, running from the anterior pronotal margin to the dorsum of the propodeum, where it forks into two fine carinae continuing posteriorly as the dorsal edges of the propodeal teeth.

(6) Postpetiolar disc broad, convex, smooth and shining, with a row of short, fine longitudinal costulae along its anterior border. Spongiform appendages of both petiole and postpetiole voluminous, gleaming white, divided by fine alveolar reticulation. Basal costulae of gaster distinct but fine, separated, 16-18 in number, occupying about the basal fifth of gastric tergite I. Remainder of gastric dorsum smooth and strongly shining.

(7) Color rather even medium ferrugineous, decidedly darker than in incerta types and lighter than is usual in rostrata.

The single paratype worker is slightly larger all around than the holotype, though the clypeus is only about 1.2 times as broad as long. TL 2.37 mm., HL 0.64 mm., WL 0.62 mm., CI 66, MI 14-15.

Type Material
The holotype worker and the paratype below were taken together by H. Okamoto at Umaji (Tosa) on the island of Shikoku, and were sent by Dr. Yasumatsu, to whom the holotype will be returned. The paratype is to be retained in the collection of the. Museum of Comparative Zoology at Cambridge.

Bolton (2000) - Holotype worker and paratype worker, JAPAN: Shikoku, Umaji (Tosa) (H. Okamoto) [examined].

References based on Global Ant Biodiversity Informatics

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 * Terayama M., S. Kubota, and K. Eguchi. 2014. Encyclopedia of Japanese ants. Asakura Shoten: Tokyo, 278 pp.
 * Yamane S., S. Ikudome, and M. Terayama. 1999. Identification guide to the Aculeata of the Nansei Islands, Japan. Sapporo: Hokkaido University Press, xii + 831 pp. pp, 138-317.
 * Yamane S., Y. Harada, and K. Eguchi. 2013. Classification and ecology of ants. Natural history of ants in Southern Kyushu. 200 pages
 * Yamane S.; Ikudome, S.; Terayama, M. 1999. Identification guide to the Aculeata of the Nansei Islands, Japan. Sapporo: Hokkaido University Press, xii + 831 pp. pp138-317.