Monomorium micrommaton

All collections have been made in rainforest on the east coast of Madagascar in the provinces of Antsiranana, Fianarantsoa and Toamasina, usually in sifted leaf litter, mould or rotten wood. The very reduced eyes and depigmented coloration suggest this species is strongly adapted to a cryptic lifeway. (Heterick 2006)

Identification
Heterick (2006) - A member of the M. flavimembra complex in the M. monomorium species group. Monomorium micrommaton workers are similar to the yellow, typical form of Monomorium termitobium, but, unlike the latter, appear to be restricted to cryptic environments. The queens are also clearly separable from those of the latter species.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar, Mayotte.

Nomenclature

 *  micrommaton. Monomorium micrommaton Heterick, 2006: 132, figs. 22, 61, 62 (w.q.) MADAGASCAR.

Worker
Holotype: HML 1.02 HL 0.39 HW 0.32 CeI 82 SL 0.27 SI 84 PW 0.22.

HML 0.92–1.11 HL 0.36–0.43 HW 0.30–0.35 CeI 78–84 SL 0.24–0.28 SI 78–87 PW 0.20–0.26 (n=20).

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 small, eye width less than 1× greatest width of antennal scape; (in full-face view) eyes set at about midpoint of head capsule; (viewed in profile) eyes set posteriad of midline of head capsule; eye more-or-less circular, or, elliptical, curvature of inner eye margin may be more pronounced than that of its outer margin. Antennal segments 12; antennal club three-segmented. Clypeal carinae indistinct; anteromedian clypeal margin emarginate, clypeal carinae indistinct; paraclypeal setae moderately long and fine, curved; posteromedian clypeal margin extending slightly beyond level of posterior margin of antennal fossae. Anterior tentorial pits equidistant from antennal fossae and mandibular insertions. 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 mainly smooth, vestigial striolae, if present, confined to lower anterior mesopleuron; (viewed in profile) promesonotum broadly convex; 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 and smooth, with a few weak striolae on metapleuron; propodeal dorsum convex; propodeum always smoothly rounded; standing propodeal setae consisting of two or more prominent pairs anteriad, often with another pair of prominent setae posteriad, and other smaller setae on/around dorsal and declivitous surfaces of propodeum; appressed propodeal setulae very sparse or absent; propodeal spiracle equidistant from metanotal groove and declivitous face of propodeum. Vestibule of propodeal spiracle distinct. Propodeal lobes present as vestigial flanges or small strips of cuticle only.

PETIOLE AND POSTPETIOLE: Petiolar spiracle lateral and situated within anterior sector of petiolar node; node (viewed in profile) cuneate, vertex tapered; appearance of node shining and smooth throughout; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) about 1:1; anteroventral petiolar process absent or vestigial; ventral petiolar lobe present; height ratio of petiole to postpetiole about 3:2; height–length ratio of postpetiole between 1:1 and 3:4; 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 yellow. Worker caste monomorphic.

Queen
HML 2.87–2.98 HL 0.67–0.70 HW 0.68–0.71 CeI 99–104 SL 0.53–0.58 SI 76–82 PW 0.74–0.96 (n=5).

HEAD: Head square; vertex always planar; frons shining and smooth except for piliferous pits; frons a mixture of incurved, semi-erect setae and slightly shorter decumbent setae. Eye elliptical, outer margin may be shallowly concave; (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; pronotum ,mesoscutum and mesopleuron shining and mainly smooth, vestigial striolae, if present, confined to anterior katepisternum; length-width ratio of mesoscutum and scutellum combined between 2:1 and 3:2. Axillae narrowly separated (i.e., less than width of one axilla). Standing pronotal/mesoscutal setae consisting of a mixture of incurved, semi-erect setae and slightly shorter decumbent setae; appressed pronotal, mescoscutal and mesopleural setulae few, mainly on sides of pronotum and mesopleuron. Propodeum shining and smooth, metapleuron with a few distinct striolae; propodeum smoothly rounded or with indistinct angle; propodeal dorsum convex; 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 vestigial flanges only, or absent.

WING: Wing not seen (queens dealated).

PETIOLE AND POSTPETIOLE: Petiolar spiracle lateral and situated within anterior sector of petiolar node; node (viewed in profile) cuneate, vertex tapered, to cuneate, vertex rounded; appearance of node shining, with vestigial sculpture; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) between 4:3 and 1:1. Anteroventral petiolar process absent or vestigial; height ratio of petiole to postpetiole between 4:3 and 1:1; height–length ratio of postpetiole between 2:1 and 4:3; postpetiole shining and smooth to shining, with vestigial sculpture; postpetiolar sternite without anterior lip or carina, or this structure vestigial.

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 bright orange-yellow. Brachypterous, alates not seen. Ergatoid or worker-female intercastes not seen.

Type Material
Holotype: worker, Prov. Toamasina, P.N. Mantadia 895 m, 18º47′5″S, 48º25′6″E, 28.xi–1.xii.1998 H.J. Ratsirarson 112/sifted litter (leaf mold, rotten wood) rainforest/112(32)–51. Paratypes: Prov. Toamasina (all specimens with same collection data as holotype): 32 workers + 1 queens ; 42 workers + 1 queen ; 32 workers + 1 (CAS); 42 workers + 1 queen.

Etymology
Greek ‘mikrommatos’ (‘small-eyed’)

References based on Global Ant Biodiversity Informatics

 * Goodman S., Y. Anbdou, Y. Andriamiarantsoa, B. L. Fisher, O. Griffiths, B. Keitt, J. J. Rafanomezantsoa, E. Rajoelison, J. C. Rakotonirina, L. Ranaivoarisoa et al. 2017. Results of a biological inventory of the Nosy Ankao island group, Parc National de Loky-Manambato, northeastern Madagascar. Malagasy Nature, Association Vahatra, 2017, 11, 
 * Heterick B. 2006. A Revision of the Malagasy Ants Belonging to Genus Monomorium Mayr, 1855 (Hymenoptera: Formicidae). Proceeding of the California Academy of Sciences (PCAS) 57: 69-202