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Figs. 34, 83-84.
Monomorium fossulatum subsp. sechellense EmeryHNS, 1894a: 69, fig. ([[worker]]). Syntype"s (lectotype here designated). Seychelles: Marianne (MCSN) [examined]. Syn. under Monomorium fossulatum WilsonHNS and Taylor, 1967:64. Syn. under Monomorium sechellense BoltonHNS, 1995: 267 [ sechellenseHNS has priority over fossulatumHNS as senior synonym].
Material examined.- Lectotype: [[worker]], Seychelles, Marianne, C. Alluaud, 1892 (MCSN). The erection of the lectotype fixes the name of this widespread taxon, whose populations vary chiefly in the degree of cephalic punctation. Paralectotype: [[worker]], same data as above (MCSN). (Carded specimen removed from same pin as lectotype above and repinned, together with new labels.)
Other material examined: Prov. Mahajanga: P.N. Ankarafantsika, Ampijoroa, 5.4 km 331 NW Andranofasika 30.iii.2001 Rabeson et al. (1 [[worker]]); P.N. Namoroka, 9.8 km 300 WNW Vilanandro, 4-8.xi.2002 Fisher et al. (18 [[worker]], 6 [[queen]]); P.N. Namoroka, 17.8 km 329 WNW Vilanandro, 8-12.xi.2002 Fisher et al. (11 [[worker]], 3 [[queen]]); PN. Tsingy de Bemaraha, 3.4 km 93 E Bekopaka 6-10.xi.2001 Fisher et al. (8 [[worker]]). Prov. Toliara: Cap Sainte Marie, 14.9 km 261 W Marovato 13-19.ii.2002 Fisher et al. (6 [[worker]]); Fiherenana, Frontier Project 21-24.x.2002 MGF040 (7[[worker]]); Foret Mahavelo, Isantoria Riv., 5.5 km 37 NE Ifotaka 31.i.2002 Fisher et al. (1 [[worker]]); 28 km NNW Ranohira, Isalo N. P., 16.xii.1993 G. D. Alpert (6 [[worker]]) (MCZ).
Worker description.- Head: Head rectangular; vertex planar or weakly concave; frons shining and smooth except for piliferous pits; pilosity of frons a mixture of incurved, semi-erect setae and slightly shorter decumbent setae. Eye minute, eyes consisting of one or two ommatidia only; (in full-face view) eyes set at about midpoint of head capsule; (viewed in profile) eyes set posteriad of midline of head capsule. Antennal segments 12; antennal club three-segmented. Clypeal carinae always weakly defined; anteromedian clypeal margin straight between strongly divergent clypeal carinae, clypeus descending almost vertically to horizontal arc of mandibles and sometimes transversely carinate below level of antennal insertions; paraclypeal setae moderately long and fine, curved; posteromedian clypeal margin extending slightly beyond level of posterior margin of antennal fossae. Anterior tentorial pits situated nearer mandibular insertions than antennal fossae. Frontal lobes sinuate, divergent posteriad. Psammophore absent. Palp formula 2,2. Mandibular teeth four; mandibles linear-triangular and smooth (except for piliferous pits); masticatory margin of mandibles strongly oblique; basal tooth approximately same size as t3 (four teeth present).
Mesosoma: Promesonotum shining and smooth on dorsum, lower mesopleuron strongly punctate; (viewed in profile) anterior promesonotum smoothly rounded, thereafter more-or-less flattened, promesonotum on same plane as propodeum; promesonotal setae greater than twelve; standing promesonotal setae a mixture of well-spaced, distinctly longer, erect and semi-erect setae which are curved distally and often paired, interspersed with much shorter, incurved, decumbent setae; appressed promesonotal setulae few, mainly on sides of promesonotum. Metanotal groove strongly impressed, with distinct transverse costulae. Propodeum shining, dorsum and sides of propodeum mainly smooth, with weak to strong striolae on declivitous face, metapleuron also with weak to strong striolae; propodeal dorsum flat throughout most of its length; propodeum distinctly angulate, propodeal angles produced as short denticles; length ratio of propodeal dorsum to its declivity about 1:1; standing propodeal setae consisting of one prominent pair anteriad, with a few to many erect to decumbent setae on/around dorsal and declivitous faces of propodeum; appressed propodeal setulae very sparse or absent; propodeal spiracle equidistant from metanotal groove and declivitous face of propodeum. Vestibule of propodeal spiracle absent or not visible. Propodeal lobes present as vestigial flanges or small strips of cuticle only.
Petiole and postpetiole: Petiolar spiracle lateral and situated slightly anteriad of petiolar node; node (viewed in profile) conical, vertex rounded; appearance of node shining and smooth throughout; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) about 4:3; anteroventral petiolar process absent or vestigial; ventral petiolar lobe absent; height ratio of petiole to postpetiole between 4:3 and 1:1; height -length ratio of postpetiole between 4:3 and 1:1; postpetiole shining and smooth; postpetiolar sternite without anterior lip or carina, or this structure vestigial.
Gaster: Pilosity of first gastral tergite consisting of a mixture of incurved, semi-erect setae and slightly shorter decumbent setae.
General characters: Color pale, depigmented yellow. Worker caste monomorphic.
Lectotype measurements: HML 1.12 HL 0.41 HW 0.34 CeI 83 SL 0.31 SI 91 PW 0.23.
Other worker measurements (non-types): HML 1.07-1.24 HL 0.40-0.45 HW 0.33-0.36 CeI 78-84 SL 0.31-0.35 SI 94-100 PW 0.22-0.25 (n=20).
Queen description.- Head: Head square; vertex weakly concave or planar; frons shining and finely longitudinally striolate and microreticulate; pilosity of frons a mixture of incurved, semierect setae and slightly shorter decumbent setae. Eye elliptical, curvature of inner eye margin may be more pronounced than that of its outer margin; (in full-face view) eyes set at about midpoint of head capsule; (viewed in profile) eyes set posteriad of midline of head capsule.
Mesosoma: Mesoscutum broadly convex anteriad, convexity reduced posteriad; pronotum, especially, also mesoscutum and mesopleuron shining with scattered punctation, otherwise smooth; length -width ratio of mesoscutum and scutellum combined between 2:1 and 3:2; axillae separated by width of at least one axilla; standing pronotal/mesoscutal setae a mixture of well-spaced, distinctly longer, erect and semi-erect setae which are curved distally, interspersed with much shorter, incurved, decumbent setae; appressed pronotal, mescoscutal and mesopleural setulae very sparse or absent; propodeum shining, uniformly weakly striolate; propodeum distinctly angulate, propodeal angle sharp; propodeal dorsum sloping posteriad, and depressed between raised propodeal angles; standing propodeal setae consisting of up to a dozen or more longer erect and shorter sub-erect setae; appressed propodeal setulae very sparse or absent; propodeal spiracle nearer metanotal groove than declivitous face of propodeum; propodeal lobes present as well-developed, rounded flanges.
Wing: Wing not seen (queens dealated).
Petiole and postpetiole: Petiolar spiracle lateral and situated well anteriad of petiolar node; node (viewed in profile) cuneate, vertex tapered; appearance of node shining and microreticulate; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) about 4:3; anteroventral petiolar process absent or vestigial; height ratio of petiole to postpetiole about 1:1; height -length ratio of postpetiole about 4:3; postpetiole shining and microreticulate; postpetiolar sternite depressed at about its center, with anterior process developed as a short, conspicuous spur angled at 45-90.
Gaster: Pilosity of first gastral tergite consisting of a mixture of incurved, erect and semi-erect setae and slightly shorter decumbent setae.
General characters: Color brown. Brachypterous alates not seen. Ergatoid or worker-female intercastes not seen.
Queen measurements: HML 1.68-1.78 HL 0.48-0.51 HW 0.45-0.46 CeI 90-96 SL 0.42-0.43 SI 91-93 PW 0.41-0.43 (n=9).
Remarks.- Its sculptured mesopleuron immediately enables the Monomorium sechellenseHNS worker to be distinguished from the worker of M. cryptobiumHNS and M. modestumHNS. Queens are larger, darker and more heavily sculptured than those of M. cryptobiumHNS. As has been the case with M. modestumHNS, sifted litter has been the most effective collection method for individual workers of M. sechellenseHNS, though one small nest series was taken from a rotten log. The species is found in dry tropical forest and gallery forest habitats in Antsiranana, Mahajanga and Toliara Provinces. Outside of Madagascar, this species has a wide distribution in the Indo-Pacific region (e.g., Bolton 1987; Wetterer 2002) and probably also occurs in Australia (Heterick 2001).