Mystrium barrybressleri Yoshimura & Fisher

Yoshimura, Masashi & Fisher, Brian 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, pp. 1-99: 25-31

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Mystrium barrybressleri Yoshimura & Fisher

sp. n.

Mystrium barrybressleri Yoshimura & Fisher  sp. n. Figs 8B, 10A, 10C, 13A, 13C, 14A, 31A, 31C, 33 A–C, 34 A–C, 35 A–B, 36A, 36C, 36E, 37A, 38A, 39A, 40A, 41A, 42A


Worker: CASENT0129838, BLF15450, MADAGASCAR, Toliara, Forêt Ivohibe 55.0 km N Tolagnaro (-24.569°, 47.204°), 200 m alt., 2-4.xii.2006, B.L.Fisher et al. leg. [CASC].


2 workers: CASENT0129839 [BMNH], CASENT0129840 [MHNG], same data as holotype.


Description. Measurements: holotype. HL 1.26, HW 1.14, SL 0.69, ML 1.08, HD 0.72, WL 1.18, PnW 0.63, PpW 0.50, PtW 0.56, PtL 0.28, CI 90.5, SI 60.7, MI 94.5, PpI 79.7, PtI 198.2.

HL 0.79-1.52, HW 0.71-1.49, SL 0.46-0.89, ML 0.67-1.41, HD 0.47-0.91, WL 0.85-1.51, PnW 0.46-0.78, PpW 0.36-0.60, PtW 0.39-0.68, PtL 0.19-0.30, CI 89.7-100.4, SI 56.0-69.9, MI 86.4-97.5, PpI 77.1-87.5, PtI 199.0-227.8 (10 specimens measured).

Posterolateral corner of head strongly to moderately expanding posteriorly. Posterior face of vertex forming slightly blunt angle with dorsal face on median line of head, so that declivity of vertex on lateral part slightly steeper than on median part. Ventral half of vertex sculptured. Eye small, only with several ommatidia. Anterior margin of clypeus convex with long, conical setae, of which median pair larger than adjacent pair. Genal tooth of head moderately developed, reaching about half of lateral lobe of clypeus. Masticatory margin of mandible slightly visible in full-face view, and dorsal surface on distal portion of mandible slightly wider than that on mandibular shaft. Second maxillary palpomere shorter than third. First flagellomere (third antennal segment) about 0.5 × length of pedicel (second antennal segment). Central part of pronotal dorsum strongly to weakly, and regularly reticulate. Lateral surface of pronotum strongly and regularly reticulate on its posterior portion. Mesonotum distinct in dorsal view, its length slightly shorter than that of propodeum. Metanotal groove shallowly impressed and mesonotum higher than pronotum in lateral view. No carina present on dorsal edge of metapleural gland bulla. Petiole extremely wide in dorsal view (PtI>195).

Body color yellowish brown to reddish brown.


Description. Measurements: HL 1.43, HW 1.52, SL 0.88, ML 1.10, HD 0.99, WL 2.05, MnW 1.23, PtW 1.12, PtL 0.46, CI 106.8, SI 58.0, MI 72.1, MnI 80.8, PtI 243.1 (one specimen measured).

Wings present and well developed. Wing sclerites fully developed even if wings have been removed. Posterolateral corner of head moderately expanding posteriorly; expansion weaker than that of workers. Posterior surface of vertex forming slightly blunt angle with its dorsal surface on median line of head, so that declivity of vertex on lateral part slightly steeper than on median part. Ventral half of vertex weakly sculptured, almost smooth. Eye well developed. Both anterior and lateral ocelli clearly present, median portion of lateral ocelli and posterior portion of anterior ocellus edged by blackish pigment. Anterior margin of clypeus convex with long conical setae, of which median pair larger than adjacent pair. Genal tooth of head moderately developed, reaching about half of lateral lobe of clypeus. Masticatory margin of mandible visible in full-face view, and width of dorsal surface on distal portion slightly wider than that on mandibular shaft. Spoon-shaped seta present on basal side of each basal denticle on masticatory margin of mandible. First flagellar segment on antenna short, about 0.5 × length of pedicel. Setae on pronotum almost simple, narrowing distally with strongly sharpened apex. Propodeal declivity in lateral view straight, making right angle with its dorsal margin. Petiole wide and short in dorsal view, 0.25 × length of abdominal segment III.

Body color yellow to yellowish brown.


Description. Measurements: HL 0.72-0.86, HW 0.91-1.17, SL 0.16-0.22, EL 0.39-0.45, WL 1.28-1.78, MnW 0.81-1.22, CI 126.8-137.5, SI 16.7-18.9, EI 52.5-55.7, MnI 88.8-108.2 (5 specimens measured).

Eye moderately large, occupying 0.6 × 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 small. Lateral ocellus small and distant from eye: distance between these more than 2 × maximum diameter of lateral ocellus. Posterior half of vertex clearly differentiated from its dorsal half, its dorsal face distinctly shorter than its posterior face. Palpal formula 4,3. First segment of maxillary palp flattened and distinctly wider than second segment. Second maxillary palpomere shorter than third. Notauli weakly impressed on mesoscutum, but often unclear or absent. Petiole in dorsal view thin, its length 0.5 × that of abdominal tergite III. Petiolar dorsum covered with fine punctures. Abdominal tergum VIII without deep punctures, almost smooth.

Distal portion of abdominal sternum IX smooth and not punctured. Basal ring quite short, not extending basally. Telomere slightly extending distally more than digitus. Bas oventral expansion of aedeagus well developed basoventrally, distinctly longer than dorsal extension. Ventral margin of aedeagus gently curved ventrally in lateral view. Aedeagus moderately narrowing distally on its distal half and its distal portion narrowly rounded.

On forewing, cu-a usually located at junction of Media (M) and Cubitus (Cu), sometimes slightly basal from junction.

Body color reddish brown to blackish brown.


The specific epithet is the patronym of Dr. Barry Lee Bressler, retired physicist, former adjunct professor of physics at Virginia Polytechnic Institute and State University, and amateur naturalist, in recognition of his interest in myrmecology and his support for research on ants.


MADAGASCAR: as in Figure 42A.

Additional material examined.

In addition to the type material, specimens from the following localities were examined in this study: MADAGASCAR. Diego-Suarez. Sakalava Beach [vegetated beach dunes] (-12.26278°, 49.3975°), across sandy trail in dwarf littoral forest, 10 m alt.; Montaigne Francais (-12.325°, 49.33333°), along forested limestone ridge, 150 m alt.; 7 km N Joffreville [camp 2 of Fisher] (-12.33333°, 49.25°), in dry forest, 360 m alt.; Parc National Montagne d’Ambre [1st campsite] (-12.51444°, 49.18139°), rainforest, 960 m alt.; [Petit Lac road] (-12.52028°, 49.17917°), rainforest, 1125 m alt.; Antsiranana. Forêt de Binara, 9.4 km 235° SW Daraina (-13.26333°, 49.6°), montane rainforest, 1100 m alt.; 9.1 km 233° SW Daraina (-13.26333°, 49.60333°), rainforest, 800 m alt.; Ampasindava, Forêt d’Ambilanivy, 3.9 km 181° S Ambaliha (-13.79861°, 48.16167°), rainforest, 600 m alt.; R.S. Manongarivo, 10.8 km 229° SW Antanambao (-13.96167°, 48.43333°), rainforest, 400 m alt.; Manongarivo, 12.8 km 228° SW Antanambao (-13.97667°, 48.42333°), rainforest, 780 m alt.; 14.5 km 220° SW Antanambao (-13.99833°, 48.42833°), montane rainforest, 1175 m alt.; Parc National de Marojejy, Manantenina River, 27.6 km 35° NE Andapa, 9.6 km 327° NNW Manan tenina (-14.435°, 49.76°), rainforest, 775 m alt.; 28.0 km 38° NE Andapa, 8.2 km 333° NNW Manantenina (-14.43667°, 49.775°), rainforest, 450 m alt.; SAVA Region, district of Sambava, Marojejy National Park, 5 km W of Manantenina village, 1st campsite (Mantella) (-14.43817°, 49.774°), low altitude rainforest, 487 m alt.; Forêt Ambanitaza, 26.1 km 347° Antalaha (-14.67933°, 50.18367°), rainforest, 240 m alt.; 6.5 km SSW Befingotra, Rés. Anjanaharibe-Sud (-14.75°, 49.5°), rainforest, 875 m alt.; Fotodriana, Cap Masoala (-15.69694°, 50.27028°), lowland rainforest, 25 m alt.; Toamasina. Montagne d’Akirindro 7.6 km 341° NNW Ambinanitelo (-15.28833°, 49.54833°), rainforest, 600 m alt.; Réserve Spéciale Ambatovaky, Sandrangato river (-16.7633°, 49.26692°), rainforest, 520 m alt.; (-16.81753°, 49.29498°), rainforest, 360 m alt.; Ile Sainte Marie, Forêt Ambohidena, 22.8 km 44° Ambodifotatra (-16.82433°, 49.96417°), littoral rainforest, 20 m alt.; Parc National de Zahamena, Tetezambatana forest, near junction of Nosivola and Manakambahiny Rivers (-17.74298°, 48.72936°), rainforest, 860 m alt.; Onibe River (-17.75908°, 48.85468°), rainforest, 780 m alt.; Reserve Betampona, Camp Vohitsivalana, 37.1 km 338° Toamasina (-17.88667°, 49.2025°), rainforest, 520 m alt.; Réserve Naturelle Betampona, 34.1 km 332° Toamasina (-17.916135°, 49.20185°), rainforest, 550 m alt.; 34.08 km 332° Toamasina (-17.91977°, 49.20039°), rainforest, 525 m alt.; Camp Rendrirendry 34.1 km 332° Toamasina (-17.924°, 49.19967°), rainforest, 390 m alt.; F.C. Sandranantitra (-18.04833°, 49.09167°), rainforest, 450 m alt.; F.C. Andriantantely (-18.695°, 48.81333°), rainforest, 530 m alt.; Analamay (-18.80623°, 48.33707°), montane rainforest, 1068 m alt.; Ambatovy, 12.4 km NE Moramanga (-18.84773°, 48.29568°), montane rainforest, 1000 m alt.; Torotorofotsy (-18.87082°, 48.34737°), montane rainforest, marsh edge, 1070 m alt.; 7 km SE Andasibe National Park Headquarters (-18.96278°, 48.45267°), tropical forest, 1050 m alt.; Mahajanga. Réserve Spéciale Marotandrano, Marotandrano 48.3 km S Mandritsara (-16.28322°, 48.81443°), transition humid forest, 865 m alt.; Toliara. Réserve Spéciale d’Ambohijanahary, Forêt d’Ankazotsihitafototra, 35.2 km 312° NW Ambaravaranala (-18.26667°, 45.40667°), montane rainforest, 1050 m alt.; 11 km NW Enakara, Rés. Andohahela (-24.56667°, 46.83333°), rainforest, 800 m alt.; 10 km NW Enakara, Rés. Andohahela (-24.56667°, 46.81667°), rainforest, 430 m alt.; Parc National Andohahela, Col de Tanatana, 33.3 km NW Tolagnaro (-24.7585°, 46.85367°), rainforest, 275 m alt.; 2.7 km WNW 302° Ste. Luce (-24.77167°, 47.17167°), littoral rainforest, 20 m alt.; 29.5 km WNW Tolanaro, Vasiha Mt. (-24.92306°, 46.74083°), rainforest, 700 m alt.; Tsimelahy - Parcel II, Andohahela National Park, transition forest (-24.93683°, 46.62667°), transition forest, 180 m alt.; Mandena, 8.4 km NNE 30° Tolagnaro (-24.95167°, 47.00167°), littoral rainforest, 20 m alt.; Manatantely, 8.9 km NW Tolagnaro (-24.9815°, 46.92567°), rainforest, 100 m alt. Fianarantsoa. Vohiparara broken bridge, Fianarantsoa Prov. (-21.22617°, 47.36983°), high altitude rainforest, 1110 m alt.; 7 km W Ranomafana National Park (-21.25°, 47.41667°), montane rainforest, 900 m alt.; radio tower, Ranomafana National Park, Fianarantsoa Prov. (-21.25083°, 47.40717°), forest edge, mixed tropical forest, open area, 1130 m alt.; Belle Vue trail, Ranomafana National Park, Fianarantsoa Prov. (-21.2665°, 47.42017°), mixed tropical forest, 1020 m alt.; Parc National de Ranomafana, Vatoharanana River, 4.1 km 231° SW Ranomafana (-21.29°, 47.43333°), montane rainforest, 1100 m alt.; 7.6 km 122° Kianjavato, Forêt Classée Vatovavy (-21.4°, 47.94°), rainforest, 175 m alt.; 36 km S Ambalavao, Rés. Andringitra (-22.2°, 46.96667°), montane rainforest, 820 m alt.; 45 km S. Ambalavao (-22.21667°, 47.01667°), rainforest, 785 m alt.; 43 km S Ambalavao, Rés. Andringitra (-22.23333°, 47°), rainforest, 825 m alt.; 9.0 km NE Ivohibe (-22.42667°, 46.93833°), rainforest, 900 m alt.; R.S. Ivohibe, 7.5 km ENE Ivohibe (-22.47°, 46.96°), rainforest, 900 m alt.; Manombo Special Reserve, 32 km SE of Farafangana (-23.02183°, 47.72°), lowland rainforest, 36 m alt.; Parc National Befotaka-Midongy, Papango 27.7 km S Midongy-Sud, Mount Papango (-23.83517°, 46.96367°), rainforest, 940 m alt.


The workers of Mystrium barrybressleri  can be distinguished from other Mystrium  workers and queens in the Malagasy region by a combination of the following characters: mesosoma lacking wing-sclerites; first flagellomere (third segment of antenna) shorter than pedicel (second segment of antenna) (as in Fig. 10C); and second maxillary palpomere shorter than third (Fig. 13C). The wider petiole in dorsal view (Figs 35A, B) separates Mystrium barrybressleri  workers from the other Mystrium  workers in the Malagasy region. A combination of smaller body size, small lateral ocelli distant from the eye (as in Fig. 26B), rounded posterior margin of head with protruding lateral ocelli in full-face view (Fig. 31A), cu-a on the forewing located at junction of Media (M) and Cubitus (Cu) (Fig. 31C), wide and short petiole in dorsal view, and fine punctation on abdominal tergite III separates Mystrium barrybressleri  males from other known Mystrium  males in the Malagasy region.

The workers of Mystrium barrybressleri  are most similar to those of Mystrium camillae  Emery. Mystrium camillae  appears to be a complex of several species (see discussion in Mystrium camillae  ) but we did not have sufficient material to fully evaluate the castes and worker variation throughout the range of the species complex. Mystrium barrybressleri  workers can be distinguished by the shape of the propodeum. In workers, the lateral portion of the propodeum is steeply and strongly convex in Mystrium  “camillae” (Fig. 33D), while the convexity is gentle and weak in Mystrium barrybressleri  (Fig. 33C). Also, in Mystrium barrybressleri  , minor workers have setae much narrower and simpler than those of major workers (Fig. 35A: major vs. 35B: minor), while in Mystrium  “camillae” minor and major workers have similar setae.

There are additional differences with Mystrium camillae  (sensu stricto, as defined by the syntype series from Myanmar). The pair of spatulate setae on the anteromedial portion of clypeus is distinctly longer in Mystrium barrybressleri  (Fig. 34C) than those in the syntype series of Mystrium camillae  (Fig. 34D). The queen of Mystrium barrybressleri  can be distinguished by the presence of simple setae on the pronotum, while in Mystrium camillae  sensu stricto, the setae are clavate. Additional diagnostic characters can be presented once the species limits are further refined for Mystrium camillae  and related species.

Mystrium barrybressleri  is found from the rainforests and montane rainforests, and the distribution pattern of this species is similar to that of a forest species Tetramorium andrei  Forel ( Hita Garcia and Fisher 2012: fig. 141). No remarkable difference was observed between specimens from NW Ambaravaranala (-18.26667°, 45.40667°) and those from the other localities, even the former forest is currently isolated from the others.