Figs. 29, 75-76.
Syllophopsis cryptobia Santschi, 1921b: 119, fig. 2 ([[worker]]). Holotype: [[worker]], Democratic Republic of Congo (NHMB) [examined].
Monomorium cryptobium Bolton , 1987: 421.
Material examined.- Holotype: [[worker]], Congo, La Moult (NHMB - Reg. No. 202). In his publication Santschi indicates he examined just the one worker. The label does not mention that it is a type, but the details on the labels are consistent with type status, as is the fact that the specimen lacks a left antennal funiculus. The funiculus of the left antenna is mounted between two cover slips that are held on a separate pin. The identification label on this pin mentions that the funiculus comes from a type specimen.
Other material examined: Prov. Antsiranana: Nosy Be, Res. Lokobe, 6.3 km 112 ESE Hellville 19-24.iii.2001 Fisher et al. (5 [[worker]], 2 [[queen]]); Reserve Speciale Ambre, 3.6 km 235 SW Sakaramy 20-26.i.2001 Fisher et al. (3 [[worker]]); Reserve Speciale Ambre, 3.5 km 235 SW Sakaramy 26-31.i.2001 Fisher et al. (7 [[worker]]); R.S. Manongarivo, 12.8 km 228 SWAntanambao 11.x.1998 BL. Fisher (18[[worker]], 10[[queen]]); R. S. Manongarivo, 14.5 km 220 SWAntanambao 20.x.1998 BL. Fisher (14 [[worker]], 2 [[queen]]); R. S. Manongarivo, 10.8 km 229 SWAntanambao 8.xi.1998 BL. Fisher (12[[worker]], 4[[queen]]). Prov. Mahajanga: P.N. Ankarafantsika, Ampijoroa, 5.4 km 331 NW Andranofasika 30.iii.2001 Rabeson et al. (61 [[worker]], 20 [[queen]]); P.N. Tsingy de Bemaraha, 10.6 km 123 ENE Bekopaka 16-20.xi.2001 Fisher et al. (14 [[worker]]). Prov. Toliara: Cap Sainte Marie, 14.9 km 261 W Marovato 13-19.ii.2002 Fisher et al. (8 [[worker]]); Foret Mahavelo, Isantoria Riv., 5.5 km 37 NE Ifotaka 31.i.2002 Fisher et al. (1 [[worker]], 1 [[queen]]); Foret de Petriky, 12.5 km W 272 Tolagnaro 22.xi.1998 BL. Fisher (1 [[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 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 weakly to strongly defined; anteromedian clypeal margin straight; paraclypeal setae moderately long and fine, curved; posteromedian clypeal margin not distinct in specimens seen. 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), or, a small to minute denticle or angle, much smaller than 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, thereafter more-or-less flattened, promesonotum on same plane as propodeum; promesonotal setae greater than twelve; standing promesonotal setae consisting of a mixture of incurved, semi-erect 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, with a few weak striolae on metapleuron; propodeal dorsum sloping posteriad, and depressed between raised propodeal angles; propodeum distinctly angulate, propodeal angle sharp; 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 nearer metanotal groove than 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 tapered, or, 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 4:3; height -length ratio of postpetiole about 4:3; postpetiole shining and smooth; 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, semi-erect setae and slightly shorter decumbent setae.
General characters: Color pale yellow. Worker caste monomorphic.
Holotype worker measurements: HML 0.99 HL 0.38 HW 0.32 CeI 84 SL 0.30 SI 92 PW 0.21.
Other worker measurements: HML 0.91-1.04 HL 0.34-0.39 HW 0.27-0.30 CeI 76-85 SL 0.27-0.30 SI 92-100 PW 0.19-0.22 (n=20).
Queen description.- Head: Head rectangular; 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, margin sometimes shallowly concave; (in fullface view) eyes set at about 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 3:2 and 4:3; 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 distinctly angulate, propodeal angles produced as short denticles; propodeal dorsum slightly elevated anteriad and sloping away posteriad, propodeal angles not raised, or, sloping posteriad, and depressed between raised propodeal angles; standing propodeal setae consisting of one pair of prominent setae anteriad, with a few smaller, erect to decumbent setae on and around dorsal and declivitous faces; appressed propodeal setulae very sparse or absent; propodeal spiracle nearer declivitous face of propodeum than metanotal groove; propodeal lobes present as well-developed, rounded flanges.
Wing: Wing veins tubular and strongly sclerotised; vein m -cu present as an entire vein enclosing first discoidal cell; vein cu -a present.
Petiole and postpetiole: Petiolar spiracle lateral and situated well anteriad of petiolar node; node (viewed in profile) conical, vertex tapered; appearance of node shining, with vestigial sculpture; 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 between 4:3 and 1:1; height -length ratio of postpetiole between 3:2 and 4:3; postpetiole shining, with vestigial sculpture; 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 head light brown, mesosoma and gaster brownish-yellow, legs pale. Brachypterous alates not seen. Ergatoid or worker-female intercastes not seen.
Queen measurements: HML 1.27-1.40 HL 0.36-0.40 HW 0.33-0.36 CeI 88-92 SL 0.30-0.33 SI 86-94 PW 0.29-0.33 (n=20).
Remarks.- Monomorium cryptobium was first described as Syllophopsis cryptobium by Santschi (1921), but the genus Syllophopsis was reduced to a synonym of Monomorium by Bolton (1987). Along with M. hildebrandti , this species is the most abundant of the M. hildebrandti group Monomorium in Madagascar. Monomorium cryptobium is one of three Malagasy members of this group in which the compound eye of the worker is reduced to one or two ommatidia. Workers can be separated from those of M. sechellense by their unsculptured mesopleuron, and from M. modestum by the distinctly angulate nature of the propodeum when seen in profile and by their generally smaller size (HW 0.33-0.36mm compared with 0.36-0.41mm).
Monomorium cryptobium is one of the few west and central African species to be found in Madagascar, whose Monomorium fauna is much more representative of eastern and southern Africa. As well as the holotype, I have inspected samples of M. cryptobium from these tropical African regions and they are identical with the Malagasy material. Despite its abundance and the presence of many of the small M. cryptobium queens among the CAS material, the male is unknown, and does not appear to have been collected by CAS teams (nearly all of the unassigned males in the CAS Collection clearly belong to members of the M. monomorium group). In fact, males of all the M. hildebrandti group species are very rare in the CAS collection. Possibly this is because they are not only cryptic, but their release during nuptial flights (assuming these occur) is very infrequent and of short duration. Monomorium cryptobium is widespread throughout all the forest habitats sampled by the B. Fisher team. Most specimens have been taken from sifted litter.
