Monomorium sakalavum

Monomorium sakalavum has been collected by a variety of methods in drier forested areas. Nest series have been collected from rotted twigs, sticks and logs on the ground as well as above ground. (Heterick 2006)

Identification
Heterick (2006) - A member of the M. rhopalocerum complex in the M. monomorium species group. Monomorium sakalavum is part of a complex of very common and taxonomically difficult Malagasy ants that are also well-represented in southern and east Africa. Typically, this species can be distinguished from its relatives by its distinctive glassy, brick-red mesosoma that contrasts with the light chocolate head and brown gaster. The mesosoma in profile is straight, the mesopleuron has weak to strong sculpture, and the propodeum is vaguely angulate. The petiolar node is cuneate. However, smaller, paler specimens have a more rounded mesosoma and may be mistaken for Monomorium termitobium (‘imerinense’) and Monomorium xuthosoma. In such cases the reddish to orange color of the mesosoma will help differentiate M. sakalavum from the former and its relatively much longer antennal scape will separate it from the latter.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  sakalavum. Monomorium sakalavum Santschi, 1928f: 196 (w.) MADAGASCAR. Heterick, 2006: 139 (q.m.).

Worker
Heterick (2006) - Lectotype: HML 1.35 HL 0.51 HW 0.41 CeI 81 SL 0.47 SI 115 PW 0.26. Non-types:HML 1.38–1.50 HL 0.52–0.56 HW 0.42–0.46 CeI 81–86 SL 0.47–0.50 SI 106–114 PW 0.28–0.31 (n=20).

HEAD: Head rectangular; vertex planar; frons shining and smooth except for piliferous pits; pilosity of frons a mixture of well-spaced, distinctly longer erect and semi-erect setae interspersed with shorter decumbent setae or setulae. Eye moderate, eye width 1–1.5× 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 weakly to strongly defined; anteromedian clypeal margin emarginate, clypeal carinae terminating in small denticles; 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 antennal fossae than mandibular insertions. Frontal lobes straight, parallel. Psammophore absent. Palp formula 1,2. Mandibular teeth three, plus minute, basal denticle or angle; mandibles with sub-parallel inner and outer margins, smooth (except for piliferous pits); masticatory margin of mandibles approximately vertical or weakly oblique; basal tooth a small to minute denticle or angle, much smaller than t3 (four teeth present).

MESOSOMA: Promesonotum shining and smooth on dorsum, entire lower mesopleuron usually distinctly striolate, striolae may be weak in smaller specimens; (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 very sparse or absent. Metanotal groove weakly to strongly impressed, with distinct transverse costulae which are typically broad. Propodeum shining and smooth, with a few distinct striolae on metapleuron; propodeal dorsum flat throughout most of its length; 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 distinct; propodeal lobes present as rounded flanges. Petiolar spiracle lateral and situated within anterior sector of petiolar node.

PETIOLE AND POSTPETIOLE: Node (viewed in profile) cuneate, vertex rounded; appearance of node shining and smooth throughout; 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; ventral petiolar lobe absent; height ratio of petiole to postpetiole about 4:3; height–length ratio of postpetiole about 4:3; 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 well-spaced, erect and semi-erect setae interspersed with a few appressed setulae.

GENERAL CHARACTERS: Color variable: head brown or reddish brown, mesosoma reddish-brown to orange, gaster chocolate, appendages yellowish-brown. Worker caste monomorphic.

Queen
Heterick (2006) - HML 2.17–2.46 HL 0.64–0.70 HW 0.63–0.66 CeI 93–102 SL 0.58–0.61 SI 90–96 PW 0.51–0.60 (n=6).

HEAD: Head square; vertex always planar; frons shining and smooth except for piliferous pits and a few striolae around antennal sockets and frontal carinae; pilosity of frons a mixture of well-spaced, distinctly longer erect and semi-erect setae interspersed with shorter setae or setulae, which are decumbent or appressed, longer setae thickest on vertex. Eye elliptical, margin sometimes 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 anteriad, convexity reduced posteriad; 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 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 few, mainly on sides of pronotum and mesopleuron. Propodeum shining, uniformly weakly striolate; propodeum always smoothly rounded; 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 lateroventral and situated within anterior sector of petiolar node; node (viewed in profile) cuneate, vertex tapered; appearance of node strongly rugose; ratio of greatest node breadth (viewed from front) to greatest node width (viewed in profile) between 3:2 and 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 7:3 and 2:1; postpetiole strongly rugose; postpetiolar sternite not depressed, its anterior end an inconspicuous lip or small carina.

GASTER: Pilosity of first gastral tergite consisting of well-spaced, erect and semi-erect setae interspersed with a few appressed setulae.

GENERAL CHARACTERS: Color blackish-red. Brachypterous alates not seen. Ergatoid or workerfemale intercastes not seen.

Male
Heterick (2006) - HML 1.75–2.02 HL 0.49–0.52 HW 0.51–0.54 CeI 104–106 SL 0.16–0.18 SI 30–33 PW 0.54–0.62 (n=3).

HEAD: (In full-face view) head width-mesosoma width ratio between 1:1 and 3:4; frons finely micropunctate. Compound eyes protuberant and elliptical; margin of compound eye clearly separated from posterior margin of clypeus. Ocelli not turreted. Ratio of length of first funicular segment of antenna to second funicular segment between 2:3 and 1:2. Maximum number of mandibular teeth and denticles three.

MESOSOMA: Mesoscutum broadly convex; pronotum and mesoscutum shining and mainly smooth, vestigial striolae, if present, confined to lower anterior mesopleuron; parapsidal furrows vestigial or absent; notauli absent; axillae separated by width of at least one axilla.

WING: Wing veins predominantly depigmented, with distal segments reduced to vestigial lines; vein m–cu absent; vein cu–a absent.

PETIOLE AND POSTPETIOLE: Petiolar spiracle lateral and situated within anterior sector of petiolar node; node (viewed in profile) conical, vertex tapered, bimodal in full-face view; appearance of node shining, with or without longitudinal striolae; 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 about 1:1; postpetiole dorsal sector shining and smooth, basal sector microreticulate.

GASTER: Pilosity of first gastral tergite consisting of well-spaced, semi-erect setae interspersed with a few appressed setulae.

GENERAL CHARACTERS: Color chocolate, tibiae and tarsi pale brown to off-white.

Type Material
Heterick (2006) - Lectotype: worker, Madagascar, Nosi be [= Nosy be], Decarpentries ( – Reg. No. 210). The lectotype fixes the name of the taxon for the typical, reddish form of the species with scapes that exceed the vertex of the head. The carded lectotype is the ant on the top rectangle on a pin holding three ants, each occupying one card rectangle. Paralectotypes: Two workers, data the same as for the lectotype (NHMB). The two workers occupy the second and third rectangles, respectively, on the pin mentioned above.