Strumigenys dagon

Identification
Strumigenys dagon group

Bolton (1983) - G. dagon is immediately recognizable as no other African species has such short mandibles or such a bizarre clypeal structure. Its only close relative is Strumigenys sahura and the characters separating the two:

Distribution based on Regional Taxon Lists
Afrotropical Region: Rwanda.

Nomenclature

 *  dagon. Glamyromyrmex dagon Bolton, 1983: 325, figs. 25, 32 (w.) RWANDA. Combination in Pyramica: Bolton, 1999: 1672; in Strumigenys: Baroni Urbani & De Andrade, 2007: 118. See also: Bolton, 2000: 297.

Worker
Holotype. TL 2.0, HL 0.57, HW 0.40, CI 70, ML 0.05, MI 9, SL 0.24, SI 60, PW 0.26, AL 0.52.

Mandibles appearing very short in full-face view (MI 8-9) as the apical (masticatory) margin is at a right-angle to the long axis of the head from the second tooth to the apex. Basal lamella of mandible, which is concealed by the clypeus at full closure, followed by a short diastema and a denticle. Distal to the denticle is a row of 5 large teeth which are slightly recurved, and apically two denticles which share a common base are present. In profile the upper mandibular margin curves upwards above the level of the anterior clypeal margin and the apical (masticatory) margin forms a near-vertical shallowly convex arch. Anterior clypeal margin in full-face view convex on each side of a deep median concavity, the lateral free margins of the clypeus expanded into a smoothly rounded prominent broad lobe on each side so that the outer margins of the closed mandibles intersect the anterior clypeal margin some distance medially of the anterolateral corners. Upper scrobe margins shallowly concave and feebly divergent posteriorly, the lateral margins of the occipital lobes behind this are shallowly convex and round behind into the smoothly concave occipital margin. In profile the edges of the laterally expanded clypeal lobes are greatly thickened in front of the level of the antennal insertions, the maximum thickness distinctly greater than the maximum width of the scape. Eyes present, small, situated on the ventral margin of the deep scrobe. Scapes of moderate length (SI 60), narrowly clavate and lacking projecting hairs on the leading edges. Dorsum of head with a single pair of erect fine hairs situated on each side of the midline close to the occipital margin. Otherwise the head only with very short fine simple hairs everywhere which are appressed and directed anteriorly; flagellate long hairs absent. Clypeus with scattered minute appressed pubescence only. Dorsum of clypeus, and of head in a band immediately behind the clypeus, glassy smooth. Remainder of cephalic dorsum finely and densely reticulate-punctulate. Anterior border of pronotum narrowly marginate, the sides of the pronotum immarginate anteriorly but separated from the dorsum by a blunt angle posteriorly. In profile the promesonotum dorsally forming a single convex outline which is separated from the propodeal dorsum by a small step, which appears as a transverse rim in dorsal view, the propodeum being on a slightly lower level than the mesonotum and marginate laterally. Infradental lamellae of propodeum broad, the propodeal teeth represented only by a short narrow denticle standing free of the lamella. Sides of alitrunk glassy smooth except for peripheral punctate sculpture. Pronotal dorsum unsculptured, mesonotum densely punctate, propodeum smooth anteriorly but with some punctures between the bases of the teeth. Pronotum and mesonotum each with a single pair of long erect simple hairs, the dorsum otherwise only having scattered short appressed hairs which are directed roughly towards the midline. Spongiform appendages of pedicel segments massively developed in profile. Petiole node in dorsal view unsculptured, broader than long, flanked on each side by a prominent spongiform process, the two linked across the posterior margin of the node by a narrow lamella. Disc of postpetiole glassy smooth, very broad and surrounded by spongiform or lamellate tissue on all sides. Spongiform tissue broadest posterolaterally, narrowest medially where it is contracted down to a very narrow rim along the posterior margin of the disc. Base of first gastral tergite with a spongiform strip which is thickest laterally. Basigastral costulae sparse in centre of tergite, denser laterally. Dorsal surfaces of petiole, postpetiole and gaster with sparse erect simple pilosity and also with much shorter appressed widely scattered simple hairs. Colour yellowish brown.

Paratype. TL 2.1, HL 0.59, HW 0.42, CI 71, ML 0.05, MI 8, SL 0.25, SI 60, PW 0.28, AL 0.56. As holotype.

Type Material
Holotype worker, Rwanda: Rangiro, i.1976, forest humus, 1800 m (P. Werner).

Paratype. 1 worker with same data as holotype.