Figs. 17, 48-49.
Etymology.- Greek "chnodes" ("downy")
Material examined.- Holotype: [[worker]], Prov. Toamasina, Mont Akirindro 7.6 km 341 NNW Ambinanitelo 15°17'3"S, 49°32'9"E 600 m, 17-21.iii.2003, Fisher et al. BLF8250/ sifted litter rainforest/ CASENT 0025716 8250(50) (CAS). Paratypes: Prov. Toliara (all specimens with same collection data as holotype; one worker with collection code 8250, other specimens with collection code 8322): 13 [[worker]] (ANIC); 13 [[worker]] (BMNH); 1 [[queen]] (CAS); 13 [[worker]] + 1 [[queen]] (MCZ).
Other material examined: Prov. Toliara: 6.9 km NE Ambanizana 2.xii.1993 B.L. Fisher (9 [[worker]], 2 [[queen]]). Prov. Toamasina: Mont. Akirindro, 7.6 km 341 NNW Ambinanitelo 17-21 iii.2003 Fisher et al. (25 [[worker]], 6 [[queen]]); Mont Anjanaharibe, 18.0 km 21 NNE Ambinanitelo 8-12.iii.2003 Fisher et al. (32 [[worker]], 6 [[queen]]); Mont Anjanaharibe, 19.5 km 27 NNE Ambinanitelo 12-16.iii.2003 Fisher et al. (16 [[worker]], 6 [[queen]]).
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 moderate, eye width 1-1.5x greatest width of antennal scape; (in full-face view) eyes set above midpoint of head capsule; (viewed in profile) eyes set around midline of head capsule; eye 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 straight; paraclypeal setae moderately long and fine, curved; posteromedian clypeal margin approximately level with antennal fossae. Anterior tentorial pits situated nearer antennal fossae than mandibular insertions. Frontal lobes sinuate, divergent posteriad. Psammophore absent. Palp formula 2,2. Mandibular teeth five, or, four; mandibles with sub-parallel inner and outer margins, smooth (except for piliferous pits); masticatory margin of mandibles strongly oblique; basal tooth approximately same size as t4 (five teeth present), or, 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) anterior promesonotum smoothly rounded anteriad, thereafter more-or-less flattened, promesonotum raised well above propodeum; promesonotal setae greater than twelve; standing promesonotal setae consisting of a mixture of incurved, semierect setae and slightly shorter decumbent setae; appressed promesonotal setulae few, mainly on sides of promesonotum. Metanotal groove strongly impressed, with distinct transverse costulae. Propodeum shining and smooth, metapleuron with a few weak striolae; 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 well-spaced and sparse; propodeal spiracle equidistant from metanotal groove and declivitous face of propodeum. Vestibule of propodeal spiracle absent or not visible. Propodeal lobes present as rounded flanges.
Petiole and postpetiole: Petiolar spiracle lateral and situated within anterior sector 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 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 not depressed at midpoint, its anterior end an inconspicuous lip or small carina, or, 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.
Holotype measurements: HML 1.11 HL 0.42 HW 0.34 CeI 81 SL 0.23 SI 68 PW 0.23.
Other worker measurements: HML 1.05-1.19 HL 0.41-0.44 HW 0.34-0.37 CeI 79-88 SL 0.23-0.27 SI 67-76 PW 0.23-0.27 (n=20).
Queen description.- Head: Head oval; vertex weakly concave or planar; frons shining and smooth except for piliferous pits; pilosity of frons a mixture of incurved, semi-erect 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 below midpoint of head capsule; (viewed in profile) eyes set posteriad of midline of head capsule;
Mesosoma: Anterior mesoscutum smoothly rounded, thereafter more-or-less flattened; 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, with a few distinct striolae on metapleuron; propodeum smoothly rounded or with indistinct angle; propodeal dorsum convex; standing propodeal setae consisting of two or more pairs of prominent setae anteriad, often with another pair of prominent setae posteriad, along with shorter, decumbent 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) conical, vertex rounded; appearance of node shining and smooth; 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 3:2 and 4:3; postpetiole shining and smooth; postpetiolar sternite not depressed, its anterior end an inconspicuous lip or small carina.
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 yellow. Brachypterous alates not seen. Ergatoid or worker-female intercastes not seen.
Queen measurements: HML 1.46-1.58 HL 0.45-0.51 HW 0.40-0.44 CeI 83-89 SL 0.28-0.33 SI 67-76 PW 0.29-0.35 (n=12).
Remarks.- Despite a resemblance to workers from some populations of M. termitobium , M. chnodes has several distinct features that place it apart from other small Malagasy Monomorium in the M. monomorium group. The shape of the mandible tends towards linear-triangular, not unlike that seen in the M. hanneli species group, and the dentition consists of four, occasionally five teeth or denticles of approximately equal size. The spiracle of the propodeum is large, as is that of the petiole, and the body and head are covered in abundant, downy setae. Nonetheless, molecular indicators place M. chnodes right within populations of what are here regarded as termitobium , and also close to M. platynodis . Monomorium chnodes has a restricted distribution in the Ambinanitelo region in Toamasina Province where workers and queens have been taken in sifted litter, from rotten logs and in pitfall traps in montane rainforest. This species also appears to have an association with the plant family Melistomataceae, which could be worthy of research.
