Monomorium exiguum Forel

Type location Ethiopia (Monomorium exiguum n. spec., Forel, 1894b: 85, worker) south Abyssinia, Ilg - see below
junior synonyms
bulawayensis (Monomorium (Mitara) exiguum For. v. bulawayensis n.v., Forel, 1913j: 217, worker) from Zimbabwe - see below
faurei (Monomorium (Mitara) Faurei n. sp., Santschi, 1915c: 260, illustrated, worker) from Gabon, collected at Samkita by Faure - see http://www.antweb.org/specimenImages.do?name=casent0010878
flavescens (Monomorium (Mitara) exiguum For. r. flavescens n. stirps, Forel, 1916: 418, worker) from Zaïre, collected at St. Gabriel, by Kohl (see Bolton, 1987, 1995) - see below
minutissimum (Monomorium minutissimum, Santschi, 1937d, illustrated, worker) from Angola - synonymy by Heterick (2006: 115) - see (headless) http://www.antweb.org/specimenImages.do?code=casent0010880
.

Forel's (1894b) description is at . Forel's (1913j) description of bulawayensis is at . Arnold (1916: 238) gave a translation of bulawayensis is at . Santschi's (1915c) description of faurei is at . Forel's (1916) description of flavescens is at . Santschi's (1937d) description of minutissimum is at . Bolton's modern description (1987) is at . Heterick's further description (2006: 115) is at .

In Ghana, at CRIG (B. Bolton), Kibi and Legon (D. Leston), Mampong and Tumu (P.M. Room), Boku and Pankese (C. A. Collingwood) (Bolton, 1987). Later, it was described as widespread, by Belshaw & Bolton (1994b), who found 605 workers from leaf litter samples at 16 locations in the semi-deciduous forest zone.

From Ivory Coast, at a site 40 km west of Abidjan (W.L. Brown); Cameroun, at Nko'emvon (D.A. Jackson); and throughout central and eastern Africa (Bolton, 1987). Wheeler (1922) also had it (as faurei) from Guinea, at Mamou (F. Silvestri). Bequaert (1922, p407) cited it as one of the species collected from myrmecophilous plants by Father H. Kohl, near Kisangani (Stanleyville) (as flavescens; in Forel, 1916).

The photomontage is of the type worker collated from http://www.antweb.org/specimen.do?name=casent0101870

Heterick (2006) [Heterick terminology, here rejected; notably the misuse of setae for hairs, and shorter decumbent setae/setulae (?) for pubescence]

WORKER DESCRIPTION

HEAD: Head rectangular, vertex planar or weakly concave; frons shining and smooth except for piliferous pits; pilosity of frons a mixture of well-spaced, distinctly longer erect and semi-erect hairs [setae] interspersed with pubescence [shorter decumbent setae or setulae]. Eye moderate, eye width 1–1.5× greatest width of antennal scape; (in full-face view) eyes set below 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 11; antennal club three-segmented. Clypeal carinae weakly to strongly defined; anteromedian clypeal margin straight; paraclypeal hairs 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 straight, parallel. Psammophore absent. Palp formula 2,2. 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).

ALITRUNK [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 hairs seven to twelve; standing promesonotal hairs a mixture of well-spaced, distinctly longer, erect and semi-erect hairs which are curved distally and often paired, interspersed decumbent pubescence; appressed promesonotal ?? [setulae] few, mainly on sides of promesonotum. Metanotal groove strongly impressed, with distinct transverse costulae, or, metanotal groove vestigial. Propodeum shining and smooth, with a few weak striolae on metapleuron; propodeal dorsum convex; propodeum always smoothly rounded; erect propodeal hairs consisting of one prominent pair anteriad, with other shorter hairs very sparse or absent; appressed propodeal pubescence 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 within anterior sector of petiolar node; node (viewed in profile) conical, 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 between 3:2 and 4:3; height–length ratio of postpetiole about 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 well-spaced, erect and semi-erect hairs interspersed with sparse appressed pubescence.

GENERAL CHARACTERS: Color variable, pale yellow to brown. Worker caste monomorphic

LECTOTYPE WORKER MEASUREMENTS
(M. exiguum): HML 0.93 HL 0.36 HW 0.28 CeI 78 SL 0.22 SI 79 PW 0.18
(M. exiguum bulawayense): HML 1.00 HL 0.39 HW 0.32 CeI 81 SL 0.26 SI 83 PW 0.20
(M. faurei): HML 0.88 HL 0.35 HW 0.29 CeI 83 SL 0.22 SI 76 PW 0.18
(M. exiguum flavescens): HML 0.89 HL 0.36 HW 0.30 CeI 82 SL 0.22 SI 75 PW 0.18
(M. minutissimum): No measurements taken as lectotype is headless.
Non-types: HML 0.79–0.97; HL 0.33–0.39 HW 0.26–0.29 CeI 73–81 SL 0.22–0.26 SI 81–93 PW 0.16–0.20 (n=20).

Separation of populations (in part from statements in Heterick, 2006). In his key to separate Malagasy Monomorium, Heterick had "Antennae 11-segmented; metanotal groove weakly impressed; in profile, propodeum rather elongate and petiolar node always conical, its dorsum tapered (depigmented yellow to brown)".

dark longer-headed specimens; designated as the type form by Heterick (2006: 116), as described by Forel (1894b: 85)	type form (lectotype)
populations with dark shorter headed specimens.	bulawayensis (lectotype)
slightly bicoloured appearance (yellowish-brown head and gaster; yellowish alitrunk, appendages and base of gaster (lectotype)	faurei (lectotype)
apparently similar to faurei but (perhaps) with more deeply incised metanotal groove	minutissimum (paralectotype)
populations with relatively pale workers with a strongly constricted alitrunk (mesosoma).	flavescens (lectotype)

Oxford University Museum specimens

Monomorium exiguum B Taylor det. Queen	Liberia E Poirier Liabala SLAM 4	2.iv.2013 Nimba County 07°31’06" N 08°35’34" E	SLAM trap Secondary forest 473 m asl	1
Monomorium exiguum B Taylor det.	Ghana S Sky Stephens 06G0032	2006	in dead caulinary domatia of Leonardoxa africana africana 2 workers & 1 queen	1
Monomorium exiguum B Taylor det.	Ghana S Sky Stephens 06G0087	2006		1
Monomorium exiguum B Taylor det.	Cameroun A Fotso Kuate Sample 61	28.vii.2010 Nko’ondo 03°54'30" N 11°25'58" E		2
Monomorium exiguum B Taylor det.	Cameroon Francis Feugang 7D6	29.ix.2009 Yaoundé 03°52' N 11°31" E	sur le cadavre de rat, capture par le fillet	1
Monomorium exiguum B Taylor det.	Gabon Y Braet Gabon 95	8.viii.2006 Pongara 00°34' N 09°19' E	Edge of savannah; yellow tray trap	2
Monomorium exiguum B Taylor det.	Gabon Y Braet Gabon 100	24.vii.2006 Pongara 00°34' N 09°19' E	On or under tree bark, Okoumé	1
Monomorium exiguum B Taylor det.	Gabon Y Braet Gabon 114	7-8.viii.2006 Pongara 00°34' N 09°19' E	Sesame & forest, sweep net	1
Monomorium exiguum B Taylor det. Male	Gabon Y Braet Gabon 237	14.v-11.vi.2006 Pongara 00°34' N 09°19' E	South Point Ngombe, lagoon edge malaise trap	1
Monomorium exiguum B Taylor det.	Congo Y Braet t-1-1	19.viii.2007 Brazzaville 4° 15' 33" S 15° 17' 5" E	24h pitfall trap; forest around the GERDIB laboratories; 317 m asl	1
Monomorium exiguum B Taylor det.	Congo Y Braet t-1-10	19.viii.2007 Brazzaville 4° 15' 33" S 15° 17' 5" E	24h pitfall trap; in a domestic garden near the GERDIB laboratories; 317 m asl	1
Monomorium exiguum bulawayense B Taylor det.	Ethiopia A Pauly	1-10.x.2012 Abijata N.P. 7°30' N 38°30' E	1635 m Yellow pan trap	1

Monomorium exiguum sensu stricto (Heterick, 2006, designated lectotype from original collection). The photograph from Heterick's paper is much paler than Heterick's description. the specimen below from Gabon shows the dark colour, as does the true type worker (above).

The photomontage is of a worker from Gabon, Pongara National Park; collector Yves Braet (Gabon 100; also Gabon 95)

Monomorium exiguum bulawayense lectotype designated by Heterick (2006) as populations with relatively pale workers with a strongly constricted alitrunk (mesosoma). The photomontage of the bulawayensis type from Zimbabwe is collated from http://www.antweb.org/specimen.do?name=casent0010763

The photomontage is of a dark brown worker from Ghana, collecteor S Sky Stephens, 2006 (06G--87); this appears to be close to the bulawayensis form.

Monomorium exiguum faurei lectotype designated by Heterick (2006) as having populations with a slightly bicoloured appearance (yellowish-brown head and gaster; yellowish alitrunk, appendages and base of gaster (lectotype).

Santschi's (1915c) description of faurei is -
WORKER - TL 1.3-1.5; Head a quarter longer than wide; sides slightly arcuate, posterior border feebly convex. Mandibles with 4 teeth, the inner teeth somewhat reduced. Clypeus with indistinct carinae. Eyes in anterior third of sides. Scapes reaching the posterior fifth of head; segment 1 of the funiculus as long as wide; segments 4-8 a quarter to half slimmer than long; apex of club as long as preceding eight segments together. Propodeum a little less convex than in orientale (from India) but more convex than clavicorne variety punicum (from Tunisia). Pedicel nodes equally wide; petiole a good third higher than postpetiole.
Colour deep yellow; head, two areas on each side of first gastral segment and following segments, brown yellow, except on the posterior borders. Smooth and shiny. Pilosity sparse; antennae pubescent.
Several workers from Gabon, by F. Faure; others from Guinea, at Mamou, by Silvestre (originally noted in Santschi, 1914d) as atomus stirps mictilis Forel; now regarded as sp. mictile from Ethiopia and Sudan).

See http://www.antweb.org/specimenImages.do?name=casent0010878

The photomontage is of a specimen from Ghana, collector S Sky Stephens (06G0032); this shows the bicoloured pattern, including the pale base to the gaster.

The photomontage is derived from that shown on http://sifolinia.blogspot.com/2007/11/monomorium-exiguum.html, taken by Mike Lush, Gambia, 3.iv.2007.

Nigerian specimen - probably also faurei (Taylor, 1980a: 33) TL 1.63 mm, HL 0.40, HW 0.34, SL 0.31, PW 0.23 (in my Guide as Monomorium species T²). Others TL 1.5-1.7 mm (Bolton, 1987: 388, not illustrated).
Colour yellow, head and gaster more brown. Eleven-segmented antennae. Cuticle of head translucent. Lateral mesonotum and propodeum very finely rugoreticulate. Erect hairs moderately long but relatively sparse. Otherwise as key.

In Nigeria, from CRIN (B. Bolton; B. Taylor). I collected it from a leaf on a low shrub under forest shade.

The photomontage is of a worker from Cameroun; Nko'ondo; aphid surevy; collector A Fotso Kuate (fk sp 61).

Matches the Nigeria specimen I drew in size and morphology.

Monomorium exiguum minutissimum paralectotype designated by Heterick (2006) as populations similar to faurei but (perhaps) with more deeply incised metanotal groove.

The photomontage is of a specimen apparently matching Santschi's minutissimum description and illustration, from Gabon, Pongara National Park; collector Yves Braet (Gabon 114); e.g the head shape in full face view and the lateral short low petiole.

Queen
The photomontage is of what seems likely to be a queen from Liberia, Liabala; collector E Poiriet (Liabal SLAM 4).

Monomorium exiguum queen.
The photomontage of a queen from Madagascar is collated from http://www.antweb.org/specimen.do?name=casent0027163

Male
The photomontage is of what seems likely to be a male from Gabon, Pongara National Park; collector Yves Braet (Gabon 237).