Mystrium voeltzkowi

Mystrium voeltzkowi has been collected in tropical dry forest, montane rainforest, littoral rainforest, and rainforest.

Identification
The worker of Mystrium voeltzkowi is distinguished from other Mystrium workers by the combination of the following characters: the vertex forming a blunt angle between posterior and dorsal faces on the median line of the head, small compound eye, the genal tooth of the head reaching to half of the lateral lobe of the clypeus, and a medial pair of conical setae on the clypeus that is smaller than adjacent pair. In addition, the characters of a central longitudinal furrow on the pronotal dorsum but without deep, stout striae impressed on dorsal and lateral surface of pronotum, and the posterior declivity of the propodeum convex posteriorly on the ventral half, so that the margin is somewhat rounded in lateral view, are also useful. The workers of Mystrium mirror and Mystrium shadow are quite similar to those of M. voeltzkowi, and the differences among the three species in workers are even slighter in small-sized individuals. When the comparison is made in workers within the same body size range, M. voeltzkowi can be distinguished from M. shadow by the small central clypeal conical setae, and from M. mirror by either a rounded declivity of the propodeum or smaller compound eye. The queen of M. voeltzkowi is easily distinguished from the other Mystrium queens by the mesosoma without developed wing sclerites (ergatoid: as in, the developed metanotal gland bulla expanding dorsally to the propodeal spiracle, and the brighter body color. Among males, only genital characters distinguish M. voeltzkowi from M. mirror. (Yoshimura and Fisher 2014)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  voeltzkowi. Mystrium voeltzkowi Forel, 1897c: 189, fig. 1 (w.m.) MADAGASCAR. Senior synonym of fallax: Yoshimura & Fisher, 2014: 91. See also: Menozzi, 1929d: 528.
 * fallax. Mystrium fallax Forel, 1897c: 192 (w.m.) MADAGASCAR. Subspecies of voeltzkowi: Emery, 1911d: 23. Revived status as species: Menozzi, 1929d: 532; Brown, 1960a: 170; junior synonym of voeltzkowi: Yoshimura & Fisher, 2014: 91.

Worker
Yoshimura and Fisher (2014) - Measurements: lectotype. HL 2.08, HW 2.12, SL 1.63, ML 2.67, HD 1.35, WL 2.58, PnW 1.17, PpW 1.00, PtW 0.97, PtL 0.66, CI 102.0, SI 76.9, MI 125.8, PpI 84.9, PtI 147.6.

HL 1.45–2.15, HW 1.41–2.26, SL 1.05–1.65, ML 1.47–2.72, HD 0.96–1.46, WL 1.72–2.68, PnW 0.80–1.20, PpW 0.69–1.09, PtW 0.70–1.03, PtL 0.46–0.67, CI 96.6–104.7, SI 71.7–80.1, MI 104.0–125.7, PpI 86.2–91.0, PtI 141.7–164.6 (9 specimens measured).

Posterolateral corner of head strongly expanding posteriorly. Posterior face of vertex forming blunt angle with dorsal face on median line of the head, so that declivity of vertex on lateral part distinctly steeper than on median part. Ventral half of vertex sculptured. Eye moderately small. Anterior margin of clypeus straight to weakly convex with moderately long conical setae. Genal tooth of head moderately developed, reaching about half of lateral lobe of clypeus. Masticatory surface of mandible in full-face view visible on basal half and invisible on distal half, width of dorsal surface of mandible almost identical from mandibular shaft to distal portion. Second maxillary palpomere longer than third. First flagellomere (third antennal segment) about 1.0–1.3× length of pedicel (second antennal segment). Pronotal dorsum covered with strong to weak longitudinal striae often waved and irregular, but median stria always deeply, straightly and clearly impressed. Shallow, fine longitudinal striae irregularly impressed on lateral surface of pronotum. Mesonotum not differentiated from propodeum in dorsal view in small individuals but differentiated in large individuals, its length shorter than that of propodeum. Metanotal groove indistinct in small individuals and shallowly and gently impressed in large individuals; mesonotum higher than pronotum in lateral view. Metapleural gland bulla strongly developed, so that propodeal declivity in lateral view convex posteriorly on ventral side. Petiole widened on posterior 1/4–1/2, gently narrowed anteriorly in dorsal view, anterior margin straight to gently rounded and not edged by striae.

Body color reddish brown to black. Four distal segments of antennal club brighter.

Queen
Yoshimura and Fisher (2014) - Ergatoid Measurements: HL 1.18-1.59, HW 1.12-1.63, SL 0.88-1.35, ML 1.13-1.64, HD 0.82-1.13, WL 1.56-2.34, PnW 0.70-0.99, PpW 0.70-1.14, PtW 0.68-0.95, PtL 0.38-0.57, CI 95.2-106.4, SI 76.1-85.7, MI 93.1108.7, PpI 97.1-115.9, PtI 161.8-186.9 (10 specimens measured).

Wings absent or vestigial and reduced to quite small appendages. Wing sclerites undeveloped. Posterolateral corner of head gently expanding posteriorly, expansion distinctly weaker than that in workers. Vertex usually thin, forming blunt angle between dorsal and posterior faces on median line of head, so that declivity of vertex on lateral part distinctly steeper than median part. Ventral half of vertex sculptured, not differentiated from dorsal region. Eye small but distinct. Ocelli absent. Anterior margin of clypeus straight to weakly convex with short conical setae. Genal tooth of head absent, usually even not angular, but angular in smallest individuals. Masticatory margin of mandible almost invisible in full-face view, dorsal surface on distal portion as wide as that on mandibular shaft. Spatulate seta present on basal side of each basal denticle on masticatory margin of mandible. First flagellomere (third antennal segment) moderately long, about 1.1–1.2 × length of pedicel (second antennal segment). Setae on pronotum almost simple, narrowing distally with strongly sharpened apex. Metapleural gland bulla extremely developed and expanding dorsally to propodeal spiracle, so that propodeal declivity in lateral view strongly convex posteriorly on ventral 2/3. Petiole relatively long in dorsal view, about 0.5–0.8× length of abdominal segment III.

Body color brown to reddish brown.

Male
Yoshimura and Fisher (2014) - Measurements: HL 1.27, HW 1.87, SL 0.42, EL 0.91, WL 2.97, MnW 1.72, CI 146.9, SI 22.2, EI 71.4, MnI 92.0 (1 specimen from original type series measured).

Eye quite large, occupying about 0.75× head length. Ocelli protruding from dorsal margin of head in full-face view. Dorsal margin of head in full-face view rounded. Both anterior and lateral ocelli large. Distance between lateral ocellus and eye equal to or shorter than diameter of lateral ocellus. Posterior half of vertex clearly differentiated from dorsal half, dorsal face distinctly shorter than posterior face. Palpal formula 4,3. First maxillary palpomere flattened and distinctly wider than second segment. Second maxillary palpomere longer than third. Notauli shallowly and weakly impressed on mesoscutum, but often unclear. Petiole in dorsal view thin, length 0.55× that of abdominal tergite III. Petiolar dorsum covered with shallow, irregular punctures. Abdominal tergum VIII without deep punctures, almost smooth.

Distal portion of abdominal sternum IX smooth and not punctured. Basal ring moderately long, gently expanding basally. Telomere distinctly extending distally farther than digitus. Basoventral expansion of aedeagus well developed basoventrally, distinctly longer than dorsal extension. Ventral margin of the aedeagus gently curved ventrally in lateral view. Aedeagus distinctly narrowing distally on distal half and apex rounded.

On forewing, cu-a located far basal from junction of Media (M) and Cubitus (Cu).

Body color yellowish to reddish brown.

Additional References

 * [[Media:Yoshimura, M. & Fisher, B.L. 2014. A revision of the ant genus Mystrium in the Malagasy region with description of six new species and remarks on Amblyopone and Stigmatomma.pdf|Yoshimura, M. & Fisher, B.L. 2014. A revision of the ant genus Mystrium in the Malagasy region with description of six new species and remarks on Amblyopone and Stigmatomma (Hymenoptera, Formicidae, Amblyoponinae). ZooKeys 394, 1–99.]]