Monomorium monomorium species group

based on Bolton, 1987

Species

 * Monomorium affabile
 * Monomorium altinode
 * Monomorium angustinode
 * Monomorium arboreum
 * Monomorium arnoldi
 * Monomorium balathir
 * Monomorium bequaerti
 * Monomorium bevisi
 * Monomorium binatu
 * Monomorium boerorum
 * Monomorium borlei
 * Monomorium braunsi
 * Monomorium captator
 * Monomorium crawleyi
 * Monomorium disoriente
 * Monomorium dolatu
 * Monomorium draxocum
 * Monomorium egens
 * Monomorium excensurae
 * Monomorium exchao
 * Monomorium exiguum
 * Monomorium fasciatum
 * Monomorium fastidium
 * Monomorium firmum
 * Monomorium floricola
 * Monomorium fugelanum
 * Monomorium gabrielense
 * Monomorium guillarmodi
 * Monomorium holothir
 * Monomorium inquietum
 * Monomorium iyenasu
 * Monomorium katir
 * Monomorium kelapre
 * Monomorium kineti
 * Monomorium lene
 * Monomorium lubricum
 * Monomorium madecassum
 * Monomorium malatu
 * Monomorium manir
 * Monomorium mavide
 * Monomorium mictilis
 * Monomorium mirandum
 * Monomorium musicum
 * Monomorium noxitum
 * Monomorium nuptualis
 * Monomorium occidentale
 * Monomorium pacis
 * Monomorium pallidipes
 * Monomorium paternum
 * Monomorium pulchrum
 * Monomorium rastractum
 * Monomorium rhopalocerum
 * Monomorium rosae
 * Monomorium rotundatum
 * Monomorium schultzei
 * Monomorium shilohense
 * Monomorium spectrum
 * Monomorium speluncarum
 * Monomorium springvalense
 * Monomorium sryetum
 * Monomorium strangulatum
 * Monomorium symmotu
 * Monomorium tablense
 * Monomorium taedium
 * Monomorium tanysum
 * Monomorium torvicte
 * Monomorium trake
 * Monomorium tynsorum
 * Monomorium vaguum
 * Monomorium vecte
 * Monomorium vonatu

Diagnosis
Worker Monomorphic, frequently with size variation in any series but without allometric variation. Mandibles unsculptured, the masticatory margin usually with 4 teeth which decrease in size from apex to base. More rarely the mandible with 3 teeth plus a minute basal denticle; a very few species with only 3 teeth and none with 5 teeth. Trulleum small to obliterated, when present frequently closed. Palp formula predominantly 2,2 but reduced to 1,2 in minute species. Median portion of clypeus raised, usually projecting forward anteriorly and longitudinally bicarinate but the carinae feeble or fading anteriorly in a few species. Median portion of clypeus posteriorly broader than either of the frontal lobes where it passes between them. Anterior clypeal margin without a widely separated pair of teeth although the anterior ends of the clypeal carinae may project as sharp angles or teeth. Cephalic dorsum unsculptured and glassy smooth except for scattered hair-pits. Eyes always present and distinct, size small to large (0.15-0.38 x HW) and generally with 4 or more ommatidia in the longest row. Eyes usually situated in front of the midlength of the sides in full-face view; close to or at the midlength in only a few species-complexes. Eyes roughly circular to elongate-oval in profile, never reniform or extended anterolaterally into a lobe. Head always longer than broad (CI 72-89), scapes very variable in length (SI 72-1 10). Antennae with 10 to 12 segments, terminating in a strong club of 3 segments. Metanotal groove moderately to strongly impressed, with distinct cross-ribs. Propodeal spiracle circular to subcircular. Propodeal dorsum rounding into declivity, not angulate or dentate. Promesonotal dorsum unsculptured. Propodeal dorsum usually unsculptured but rarely it may be reticulate-punctate; never transversely striate or rugulose. Petiolar spiracle at the node. Body pilosity variable in distribution but usually conspicuous, only extremely rarely absent from the dorsal alitrunk. Mesopleuron and metapleuron often smooth but may retain faint sculpture. Petiole, postpetiole and gaster usually unsculptured, very rarely otherwise. (Workers examined: all included in this revision plus about 50 extralimital forms of the group - see Bolton 1987 for species list)

Female Characters generally as worker but female much larger; female slightly smaller to slightly larger than con specific male. Eyes larger than in worker and positioned at or close to the midlength of the head. Ocelli present. Mandibles as worker but dentition much reduced or bizarre in some socially parasitic species. Antennae with 11 or 12 segments, with a 3-segmented club. HW greater than maximum width of mesoscutum or the two about equal. Alitrunk usually winged and with a full complement of flight sclerites, but several apterous forms are known (Monomorium carbonarium, Monomorium ebeninum, Monomorium floricola, Monomorium mictilis, Monomorium minimum). Alitrunk long and narrow in dorsal view, long and low in profile. Parapsidal grooves distinct to absent. Axillae triangular in dorsal view, separated by a small mid-dorsal gap or just meeting at the midline; axillae partially to entirely fused to mesoscutum in apterous females. Forewings with cross-vein m-cu absent and the venation frequently much reduced, with many veins faint to vestigial and not tubular. Head, alitrunk and gaster usually unsculptured but some with weak sculpture on the head behind the lateral portions of the clypeus and behind the frontal lobes. Lateral alitrunk sometimes sculptured in part. First gastral tergite unsculptured. Pilosity always present on dorsal surfaces of body, often abundant. (Females examined: - see Bolton 1987 for species list.)

Male Slightly smaller to slightly larger than the conspecific female, much larger than the worker. Mandibles meeting medially at full closure, with 3 teeth and frequently also with a minute basal denticle. Palp formula 2,2 or 1 ,2. Scape cylindrical or subcylindrical, variable in length but usually about equal to the second funicular segment or a little longer. First funicular segment not globular, the remainder of the funiculus not strongly tapering apically, not whip-like. Head capsule wider behind the eyes than in front, the maximum head width about equal to the maximum width of the mesoscutum. Eyes large and sited just in front of the midlength; always a space present between eye and mandibular base in full-face view, the eye not touching the clypeus. Ocelli large but not born on a turret nor breaking the outline of the occipital margin. Mesoscutum overhanging pronotum anteriorly. Notauli absent and mesoscutum usually lacking a narrow V-shaped anteromedian area which is less sculptured than the surrounding area. Parapsidal grooves present to absent. Axillae small, triangular in dorsal view and separated by a small gap medially. Propodeal spiracle in front of the midlength of the side. Venation as alate female. Head sculptured, remainder of body variable but usually smooth, sometimes the mesoscutum and scutellum sculptured. First gastral tergite unsculptured. Genitalia large and partially exserted. Body with pilosity dorsally. (Males examined: - see Bolton 1987 for species list.)

Species Complexes
Afrotropical species-complexes of the monomorium-group (based on workers)

altinode complex

 * Monomorium altinode
 * Monomorium angustinode
 * Monomorium arnoldi
 * Monomorium captator
 * Monomorium fugelanum
 * Monomorium mirandum
 * Monomorium occidentale
 * Monomorium tynsorum
 * Monomorium vonatu

This quite conspicuous complex includes 9 species which are very widely distributed in sub-Saharan Africa. The distinctive structure of the clypeus is shared with the katir-complex and the leopoldinum-complex, but both of these lack the apomorphic petiole and postpetiole configuration shown by the altinode-complex. The female of occidentale is known but otherwise all sexual forms are unknown in this complex.

The members of this complex appear to constitute a holophyletic lineage and are linked by possession of the following characters. Clypeal carinae are sharp and conspicuous, close together posteriorly and widely divergent anteriorly. The anterior clypeal margin has a prominent median section which is flanked by a pair of teeth, denticles or projecting acute angles at the apices of the clypeal carinae. Antennae 12-segmented and the scapes not reaching the occipital margin when laid straight back. With the head in full-face view the eyes are distinctly in front of the midlength of the sides; in profile the eyes are usually elongate-oval and have a maximum diameter 0.20-0.28 x HW. The head capsule in profile is somewhat dorsoventrally flattened, with the dorsum, venter or both flat to shallowly convex. Usually the head becomes deeper posteriorly. Petiole node high and narrow in profile (Figs 84-88), anteroposteriorly slightly compressed and the peduncle subtended by a small or inconspicuous anteroventral process. Postpetiole high and narrow, also anteroposteriorly compressed and with a high vertical anterior face.

bequaerti complex

 * Monomorium bequaerti
 * Monomorium pulchrum
 * Monomorium rosae

Of the species included here bequaerti is known only from Zaire, and pulchrum only from Zimbabwe, but rosae is widely distributed in west and central Africa. Males and females of rosae are known but they have not yet been found for the other two species.

A small complex containing only three species and characterized by possession of 11-segmented antennae and a relatively large postpetiole. In profile the postpetiole is equal to or somewhat more voluminous than the petiole, and has a long, gradually sloping posterior face.

boerorum complex
A large complex of 22 species comprising all those forms which do not fit any of the above complexes, and hence merely lumped here for convenience.

Seven species have 11 antennal segments and usually show reduced eyes in which a single median longitudinal row of 2-4 ommatidia is enclosed by an outer ring of ommatidia.
 * Monomorium exiguum
 * Monomorium fastidium
 * Monomorium guillarmodi
 * Monomorium mictilis
 * Monomorium spectrum
 * Monomorium taedium
 * Monomorium vaguum

A number of species with 12-segmented antennae also show a similar eye structure to that noted above.
 * Monomorium inquietum
 * Monomorium rotundatum
 * Monomorium shilohense
 * Monomorium sryetum
 * Monomorium trake

The following tramp species also has the aforementioned eye structure.
 * Monomorium floricola

The remaining species, which have 12-segmented antennae, all show a normal eye with two or more longitudinal rows of ommatidia within the outer ring. These species also tend to have a narrow blade-like subpetiolar process.
 * Monomorium boerorum
 * Monomorium braunsi
 * Monomorium kelapre
 * Monomorium lubricum
 * Monomorium mavide
 * Monomorium musicum
 * Monomorium nuptualis
 * Monomorium paternum
 * Monomorium torvicte.

Despite this there is a tendency for variation in the characters mentioned and a few exceptions to the characters. It is not possible to make any meaningful division of the complex at the present time.

The vast majority of species included here are restricted to the territories of southern Africa. Species which occur in southern Africa and elsewhere on the continent include exiguum, mictilis, and vaguum, but each of these names may conceal more than one valid species. Only three species are found away from southern Africa, namely inquietum (Zaire), spectrum (Gabon), and trake (Ghana).

iyenasu complex
Monomorium iyenasu

A single rather strange species from Tanzania, is included here. Known only from the worker it is immediately diagnosed by its relatively large size for a member of the monomorium-group (HW > 0.70), 12-segmented antennae with short scapes (SI <80), small eyes (0.19 x HW) and very dense pilosity. It lacks obvious relatives among the Afrotropical fauna and may represent an introduction from outside the region.

katir complex

 * Monomorium balathir
 * Monomorium holothir
 * Monomorium manir
 * Monomorium katir

The four large-eyed species of this small complex appear to be derived from the same source as the altinode-complex, that source may well be the leopoldinum-complex. All three share the same characteristic clypeal structure and it may be postulated that the altinode-complex consists of relatives of the leopoldinum-complex which have evolved a specialized petiolar and postpetiolar structure, whilst the katir-complex consists of relatives of the leopoldinum-complex which have evolved enlarged eyes. The female of balathir is known, males remain unknown in this complex.

The clypeus, antennae and head shape correspond to that seen in the altinode-complex but the eyes, situated in front of the midlength, are relatively very large (0.30-0.38 x HW), with their posterior margins at or very close to the midlength of the sides. Also the petiole is subconical in profile and the postpetiole rounded, lacking the characteristic shape of the foregoing complex.

leopoldinum complex

 * Monomorium borlei
 * Monomorium lene
 * Monomorium leopoldinum (now Monomorium madecassum'')
 * Monomorium pallidipes
 * Monomorium rastractum
 * Monomorium springvalense

The 6 species included here have much the same general appearance as the two complexes noted above, but they lack the specialized petiole and postpetiole of the altinode-complex and the enlarged eyes of the katir-complex. All species of the leopoldinum-complex are of eastern or southern Africa, their sexuals are not known.

Clypeus, antennae and head shape as described for the altinode-complex. Eyes in front of the midlength of the sides but of moderate size (0.18-0.27 x HW). Petiole subconical and postpetiole rounded, lacking the high narrow aspect of the altinode-complex.

malatu complex

 * Monomorium affabile
 * Monomorium disoriente
 * Monomorium malatu
 * Monomorium tanysum
 * Monomorium dolatu

Of the five species represented here four have have 12 antennal segments, while dolatu has only eleven. Most of the species are of west or central African origin but disoriente is known only from Tanzania. Sexual forms of all species remain to be discovered.

Characters of this small complex are the same as those of the strangulatum-complex, and species with both 11 and 12 antennal segments are also included here. The structure of the petiole is, however, different, the node of malatu-complex members being high and either narrowly subconical or cuneate in profile. The anterior peduncle is short and stout, and is subtended by a relatively large anteroventral process which is usually in the form of a broad, anteriorly truncated lamellate strip. In most species the standing hairs of the head, alitrunk and gaster tend to be blunt or truncated apically.

rhopalocerum complex

 * Monomorium binatu (=Monomorium termitobium)
 * Monomorium exchao (=Monomorium termitobium)
 * Monomorium rhopalocerum
 * Monomorium symmotu
 * Monomorium tablense

On the whole the five southern and eastern African species included here are remarkably similar to the members of the schultzei-complex but have shorter scapes, forward shifted eyes and somewhat more flattened heads. Females are known for exchao and rhopalocerum, males for exchao alone.

Clypeal structure as in the schultzei-complex and also matching that complex in alitrunk, petiole and postpetiole structure. Eyes in the rhopalocerum-complex are more elongate than in schultzei and allies and are very obviously situated in front of the midlength of the sides. The antennal scapes when laid straight back from their insertions fail to reach the occipital margin (except in Monomorium binatu where they just reach), and the antennae are always 12-segmented. The head capsule in profile is shallowly biconvex, its deepest point at about the midlength.

schultzei complex

 * Monomorium arboreum
 * Monomorium bevisi
 * Monomorium crawleyi
 * Monomorium excensurae
 * Monomorium fasciatum
 * Monomorium firmum
 * Monomorium kineti
 * Monomorium schultzei
 * Monomorium speluncarum
 * Monomorium vecte

The 10 species included here form a close-knit complex of related forms and probably represent a holophyletic lineage. The species are restricted to eastern and southern Africa and are apparently related to the rhopalocerum-complex, whose members share a similar overall distribution. Males of the schultzei-complex remain unknown but females of arboreum, firmum and schultzei are represented in collections.

Clypeal carinae sharp, close together, parallel or only feebly divergent anteriorly. Anterior margin of projecting median portion of clypeus without prominent acute angles, teeth or denticles. Antennae 12-segmented and relatively long (SI 95-110), the scapes when laid straight back reaching or slightly exceeding the occipital margin or rarely failing to reach the margin only by a mere fraction of their apical width. Eyes in profile appearing round or subcircular (rather than elongate-oval), in full-face view the eyes at or close to the midlength of the sides; in general the posterior margins of the eyes are at the midlength. Head capsule in profile distinctly biconvex, not dorsoventrally flattened. Head deepest just behind level of eye or close to the midlength. Promesonotum and propodeum in profile each forming a distinct convexity, separated by the metanotal groove. Petiole node small and subconical in profile. Subpetiolar process inconspicuous, either a small anteroventral lobe or a narrow strip. Postpetiole in profile low and rounded, smaller than the petiole and lacking a high vertical anterior face.

strangulatum complex

 * Monomorium draxocum
 * Monomorium egens
 * 'Monomorium gabrielense''
 * Monomorium noxitum
 * Monomorium strangulatum

Four species with 12 antennal segments, and strangulatum having only 11. Of the five all but egens are obviously closely related, but in egens the anterior clypeal margin tends to be concave and the pronotum is flattened with accentuated angular humeri; features not seen in the other four. All species occur in western and central Africa and morphologically appear intermediate between the schultzei- and rhopalocerum-complexes and the malatu-complex. They are particularly close to the latter but lack its characteristic petiolar structure. Males are not known for any species in this complex but females of egens and draxocum have been examined.

Clypeal carinae sharply developed, widely separated and only feebly divergent anteriorly. The points at which the clypeal carinae meet the anterior clypeal margin are not marked with prominent angles or denticles. Antennae with 11 or 12 segments and when laid straight back the scapes surpass the occipital margin (except in egens). With the head in full-face view the posterior margins of the eyes are approximately at the midlength of the sides. In profile the eyes are round to subcircular (rather than elongate-oval). Head capsule in profile distinctly biconvex, deepest just behind the level of the eye or at the midlength. Occipital margin usually convex in full-face view. Petiole with a long anterior peduncle, subtended by a minute anteroventral process. Postpetiole low and rounded.

Additional Resources

 * Monomorium
 * Monomorium species groups