SUBFAMILY MYRMICINAE - Genus Oligomyrmex
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The Ants of
Africa SUBFAMILY MYRMICINAE - Genus Oligomyrmex |
| Contents - Myrmicinae - MYRMICINAE Introduction |
In Tribe PHEIDOLOGETONINI. Genus in need of revision, although some examination was made by Ettershank (1966).
Diagnostic Features - Dimorphic, major workers with massive heads. Median portion of clypeus longitudinally bicarinate. Antennae 9-, 10- or 11-segmented, with a 2-segmented club. Eyes present but small. Promesonotal suture absent, metanotal groove impressed. Propodeum armed with a pair of teeth or at least sharply angulate. Yellow to deep brown.
Now [November 2007] regarded by Fernandez (2004) as in the genus Carebara
.
African subgenera Aeromyrma Forel (1891b: 198; subgenus status by Emery, 1915c: 59); Aneleus Emery (1900c: 327 as subgenus of Pheidologeton; raised to genus by Emery, 1914a: 41; senior synonymy of Sporocleptes, by Consani,1951: 169); Crateropsis (Patrizi, 1948: 174); and, Nimbamyrma (Bernard, 1953b: 240).
Mayr's (1867a) genus definition, the type specimen, a queen of O.
concinnus, with 9-segmented antennae, is at 
. Forel's (1891b) definition of Aeromyrma,
with 11-segmented antennae, is at 
and 
. Emery's (1900c) definition of Aneleus,
with 11-segmented antennae, is at 
. Patrizi's (1948) definition of Crateropsis
is at 
. Bernard's (1952) definition of Nimbamyrma
is at 
.
Bolton (1995) did not maintain any subgenera, attributing synonymisation to Ettershank (1966). The latter described examining Malpighian tubules from three undetermined species from Ivory Coast and synonymised several former genera. However, he appears to have felt separation into subgenera on the basis of the number of antennal segments might be justified; thus Aneleus has 11-joints, Aeromyrma has 10; Oligomyrmex has 9; and Octella has 8.
To show the dimorphism, I draw attention to the examples of genus members on pages of the Japanese Ant Color Image Database, of which the link is one of five pages.
According to Ettershank's review (1966) colonies are generally rather small, or broken up into small subcolonies. Collections usually come from under the bark of logs, in rotten wood, in leaf litter, or in other generally humid places. Most may be lestobiotic, probably feeding on arthropod eggs. There is no modern taxonomic revision.
Bernard (1952) not only maintained the early genera but defined a new genus Nimbamyrma. From his notes, six species of Aneleus were known but only one was taken at Mt. Nimba, Guinea, silvestrii of which he was able to describe the male, a first for the genus (see below). From Aeromyrma he wrote of 3 isolated females, each of a distinct species, taken by Lamotte at Nion (700 m), Ravine I of Mount Tô (forest). The revision by Weber (1950) had been limited by the major caste being the only well known morph. However Bernard, who described the first male of the then genus Aneleus (silvestrii, see below) noted that the male morphology suggested Aneleus might be no more than a subgenus of Oligomyrmex; although the major and minor workers had 11-segmented antennae compared to the 10-segmented antennae of Oligomyrmex. In a footnote, Bernard added that an important collection of subterranean ants, by A. Machado, had just been received by him from Angola, and that included numerous workers of Nimbamyrma.
The synonymy of Nimbamyrma (villiersi) with Oligomyrmex by Ettershank seems questionable. Bolton (1973) who refers to Ettershank, has Oligomyrmex with the clypeus bicarinate and the propodeum with a pair of teeth or at least sharply angulate. Bernard (1952) wrote of (translated) "the clypeus without carina", the propodeum has two pairs of spines, as often seen in Tetramorium species, and (perhaps by default) there is no knowledge of dimorphism in Nimbamyrma. Similarly Wheeler (1922) listing features of Aeromyrma noted clypeus without carina.
My feeling is that the distinctive species, O. (Aneleus) politus (Santschi), which appears to have only a minor worker and not a major, perhaps merits elevation to monotypic Genus status see Oligomyrmex politus for details and the synonymy of villiersi. The revisionary paper by Fernandez (2004) resolves this by placing all in Carebara, although Fernandez did not consider the likely synonymy of Nimbamyrma villiersi under O. politus.
Santschi's (1913e) early key is at 
- NOTE infimus now is in the genus
Paedalgus, and antennal counts are not used. Weber's (1952) key
to Aeromyrma is at 
. He also provided notes on the biology of
the genus, these are at 
.
Key to major or soldier morph [Key to minors]
| 0 | Queen only known; subgenus Crateropsis, head with unique sculptured dorsal concavity | Kenya - elmenteitae |
| -- | Antennae 9-segmented | subgenus Oligomyrmex |
| -- | Antennae 10-segmented (note - debilis (?) sometimes 9-segmented) | subgenus Aeromyrma |
| -- | Antennae 11-segmented | subgenus Aneleus |
| -- | subgenus Oligomyrmex | -- |
| 1 | Occiput with at least lateral tranverse carina, variably produced into a tooth at the angles | 2 |
| -- | Occiput with transverse carina, lateral angles rounded without any raised points or teeth | 5 |
| 2 |  TL
1.9 mm; HL 0.73 HW 0.48; occipitum with a carina on each side, giving a
dentate profile; head with pronounced frontal lobes; metanotal groove
broad and well-marked, propodeum dorsum and declivity with obtuse angle
and small lateral teeth; head densely reticulate punctate, pronotum
reticulate-punctate, pedicel dorsum mostly smooth; colour
brownish-yellow, gaster and mandibles darker |
Zaïre - frontalis |
| ¤ |  TL 1.4 mm, HL 0.56 HW 0.43; separable from frontalis
by the angular protuberances of the anterior frontal carinae and the
profile of the propodeum and petiole; major only known |
Chad - diabolicus |
| -- | Frontal lobes small and hardly produced posterior of the antennal insertions | 3 |
| 3 | TL 1.5 mm; HL 0.67 HW 0.50; head convex in front, occiput biconvex with a pair of lateral teeth, anterior clypeal margin produced as an emarginate lobe; eyes minute; propodeal teeth obtuse; shiny, head reticulate-punctate, pronotum dorsum smooth, rest of alitrunk and pedicel punctate, gaster smooth; colour yellowish-brown; soldier only known | Uganda - convexus |
| -- | Anterior clypeal margin with lateral carinae and straight to slightly concave anterior margin | 4 |
| 4 |  TL
1.6-1.8 mm; HL 0.6 HW 0.4; occiput with fine lateral carina terminating
laterally in a small tooth; eyes of a single facet; clypeal margin
projecting but not dentate; head and promesonotum shiny, with
piligerous puncturations, head with longitudinal striations, rest of
alitrunk and pedicel thickly punctate; pilosity short but abundant;
colour yellow, head light brown |
Ethiopia - erythraeus |
| -- |  TL
2.0 mm; HL 0.84-0.91 HW 0.55-0.58; occipital margin laterally carinate;
frontal lobes small convex and not raised; metanotal area with apparent
vestigial wing bases; propodeum with broadly divergent triangular teeth
with even concavity between; shiny, head finely striate-punctate,
alitrunk and pedicel densely and more coarsely punctate except dorsal
areas which are smooth; colour bright ferruginous with brownish -yellow
funiculi and legs |
Uganda - thoracicus |
| 5 |  TL
2.1 mm; HL 0.8, one-fifth longer than wide; occipital margin without
carinae, eyes rudimentary; metanotal groove deep but with a membranous
band, propodeal teeth reduced to points; sculpturation fine, head
longitudinally striate but very shiny, and medially smooth |
Zaïre - latro |
| -- | TL < 2.0 mm | 6 |
| 6 | Propodeum without distinct teeth; TL 1.4 mm; HL 0.60 HW 0.40-0.45; head rectangular, occipital margin broadly impressed medially, corners rounded right angles; anterior clypeal margin sinuate with lateral blunt angles formed by carinae; eyes minute, no median ocellus; metanotal suture shallow; colour yellowish- brown | CAR - donisthorpei |
| -- | Propodeum with distinct teeth, even if very small | 7 |
| 7 | HL one-fifth greater than HW | 8 |
| -- | HL at least one-quarter longer than HW | 9 |
| 8 |  TL 1.5-1.6 mm; HL one-fifth greater than HW, shorter than angolensis,
sides parallel, occipital border feebly concave; metanotal groove deep,
propodeum slightly raised declivity shorter than dorsum and concave,
small slightly raised propodeal teeth; pubescence abundant; head
reticulate-punctate except at sides, genae striate and shiny, most of
alitrunk finely reticulate-punctate, gaster smooth and shiny; colour
dull yellow, head more brown with black anterior border |
Kenya - alluaudi |
| -- |  TL
1.56 mm; head with moderately convex sides; metanotal groove deep;
colour yellow-brown |
Nigeria - new species - boltoni |
| 9 |  HL one-third greater than HW; TL 1.7 mm; propodeum with
lateral carinae, concave between; almost all except parts of head
densely punctate; colour light ferruginous |
Sudan - santschii |
| HL one-quarter greater than HW | 10 | |
| 10 |  TL
0.9-1.0 mm (but ssp congolensis TL 1.4-1.5 mm); HL one-quarter
longer than HW; propodeal teeth acute about as long as one-fourth their
interval; pubescence mainly on head and appendages; colour
reddish-yellow, head more red, gaster brownish-yellow |
? (Nigeria) species B - Angola and Zaïre - angolensis |
| -- |  TL
1.7 mm; head a quarter longer than wide, concave posteriorly, no
anterior carinae on head; mandibles six-toothed; scape reaching
mid-point of face, angles of occiput not raised; postpetiole distinctly
wider than petiole; head mostly smooth and shiny, except for fine
anterior and vertex striae; ? Aeromyrma according to inclusion
in Weber (1952) key. |
Kenya - jeanneli |
 |
subgenus Aeromyrma - based on Weber (1952) | -- |
| ¤ | Minor only known | Zambia - incertus |
| ¤ | Minor only known | Zimbabwe - khamiensis |
| ¤ | Minor only known | Zimbabwe - lucidus |
| ¤ | Minor only known | South Africa - traegaordhi |
| ¤ | Minor (queen) only known | Uganda - ugandanus |
| ¤ | Minor only known | Ghana - vorax |
| 11 | TL 2.0-2.5 mm | 12 |
| -- | TL 2.7-2.9 mm; head with anterior carinae; mandibles six-toothed; scape barely exceeding mid-point of face; occipital angles with with a small tooth or horn; head shiny but finely reticulate; colour dirty yellow, head yellowish red | Botswana - africanus |
| 12 |  Occipital border near straight |
12 |
| -- |  Occipital border deeply impressed |
15 |
| 13 |   TL 2.0 mm; eyes indistinct, head striate;
propodeum with smoothly rounded angle between dorsum and declivity;
colour of head yellowish-brown, alitrunk more brown, gaster
intermediate but anterior darker |
South Africa - arnoldiellus |
| -- | Propodeum with distinct angle between dorsum and declivity | 14 |
| 14 |  TL 2.2 mm; eyes distinct; metanotal groove
quite wide and deep; head with anterior longitudinal striation and
transverse posterior striation, occipital angles reticulate;
postpetiole one and two-thirds wider than long; colour overall
reddish-yellow, head and gaster darker |
South Africa - semilaevis |
| -- |  Head missing on sole example; metanotal groove feeble;
colour overall brownish-yellow |
Mozambique - nanus |
| 15 | Occipital angles rounded and right-angled or obtuse | 16 |
| -- | Occipital angles acute; TL 2.1 mm, HL 0.87 HW 0.55; AL
0.60; well developed propodeal spines; colour brown with head
distinctly lighter than gaster |
Zaïre - acutus |
| 16 |  Propodeum dentate; TL 2.5 mm, HL 0.84 HW 0.55; AL 0.63;
postpetiole twice as wide as long; soldier only known; colour
ferruginous |
Zaïre - petulcus |
| -- |  Propodeum edentate; size larger, TL 2.5-2.6 mm;
postpetiole one and two-thirds wider than long; occiput submatt,
densely but finely sculptured; colour reddish-yellow, gaster darker |
Guinea - debilis |
|
subgenus Aneleus | -- |
| ¤ | Queen only known | Angola - paetus |
| ¤ | Minor & queen only known | Panafrican - politus |
| ¤ | Minor only known | Kenya - punctatus |
| ¤ | Bernard in new genus Nimbamyrma - worker only (may well be synonymous with politus) | Guinea - villiersi |
| 17 |  Occiput
with lateral carination and distinct elongate processes; TL 2.4-2.6 mm;
matt and densely reticulo-punctate; colour yellow slightly rust, head
brownish-red, gaster yelllow grey |
Cameroun, CAR - diabolus |
| -- | Occiput without lateral carination | 18 |
| 18 |  Occiput
with distinct transverse margination; TL 2.0-2.5 mm; colour
reddish-yellow, head rufous and shiny, meso- and metapleura closely
punctured and dull |
East & South Africa - perpusillus |
| -- | Occiput with transverse striations but not a distinct transverse margination | 19 |
| 19 |  TL
3.2-3.5 mm; eyes very small with 2-3 ommatidia; gaster with markedly
concave anterior where postpetiole attached; occiput and dorsal
alitrunk transversely rugose; sparse yellowish pilosity; colour
rust-red, clypeus and mandibles red-brown, appendages paler |
Fernando Po I. - menozzii |
| -- |  TL
2.0-2.5 mm; mandibles 5-toothed; eye of 6-8 ommatidia; propodeum with
strong lateral margination and two strong teeth; head puncturate with
longitudinal anterior striations and transverse rugae on occiput;
alitrunk punctate, very dense on propodeum, pedicel nodes near smooth,
gaster smooth; pilosity yellowish, sharp and curved; colour testaceous
red |
Ghana & Guinea - silvestrii |
| ¤ | Queen only known; subgenus Crateropsis, head with unique sculptured dorsal concavity | Kenya - elmenteitae |
| -- | Antennae 9-segmented | subgenus Oligomyrmex |
| -- | Antennae 10-segmented (note debilis 9-segmented) | subgenus Aeromyrma |
| -- | Antennae 11-segmented | subgenus Aneleus |
| -- | subgenus Oligomyrmex | -- |
| ¤ | Major only known | Uganda - convexus |
| ¤ | Major only known | Chad - diabolicus |
| ¤ | Description inadequate; TL 0.98 mm; separation by major | Nigeria - new species - boltoni |
| 1 | TL no more than 1.0 mm | 2 |
| -- | TL 1.0-1.1 mm | 4 |
| 2 |  Pilosity
short but copious; TL 0.9 mm; head slightly longer than wide; lateral
alitrunk, head and promesonotum shiny; propodeum and pedicel densely
punctate; colour yellow-brown, head more yellow |
. |
| . |  |
Ethiopia & Gabon - erythraeus |
| -- | Pilosity thin and sparse | 3 |
| 3 | TL 0.8-1.0 mm; head a little longer than wide; mandibles 5-toothed, eyes minute; scape slightly surpassing posterior third of head; pronotum with anterior angles rounded; propodeal spines longer than one-third their basal interval; matt with a greasy reflection, mostly reticulate-punctate; colour entirely dull yellow; antennae & legs paler | Kenya - alluaudi |
| -- |  TL 0.8 mm; head a little longer than broad, longer than in
alluaudi and less enlarged behind; the scape nearly
attains the posterior fourth of the head; mandibles of four teeth;
alitrunk broad in front and more marginate than in alluaudi;
basal face of the propodeum clearly broader than long, with the teeth
moderate, somewhat broader at the base than long; petiole a little
longer than high and a little broader at the summit than in alluaudi;
postpetiole rounded, narrower. Head, propodeum, and sides of the
petiole matt, densely and finely reticulate-punctate, the remainder
smooth and shining; colour reddish yellow |
Angola & Gabon - angolensis |
| 4 | Propodeum with distinct triangular teeth | 5 |
| -- | Propodeum with no more than small points | 6 |
| 5 |  TL 1.1 mm; head nearly 1.2 longer than wide; mandibles
5-toothed; anterior clypeal margin produced as a sinuate lobe over base
of mandibles; eyes minute; frontal lobes well developed and convex not
concealing antennal insertions; propodeum with small triangular teeth;
sublucid, all except pronotum and gaster with fine dense puncturation;
colour yellowish-brown, antennae and legs paler |
CAR - donisthorpei
or Sudan - santschii |
| -- |  TL
1.1 mm; head less than 1.2 times longer than wide; mandibles with fine
acute teeth; propodeal spines short and triangular, declivity laterally
carinate; sublucid, densely punctate except on gaster, pronotum and
dorsum of pedicel nodes; brownish-yellow |
Zaïre - frontalis |
| 6 |  TL
1.0-1.1 mm; head one-eighth longer than wide; propodeum sub-dentate;
mostly smooth, propodeum and lateral mesonotum reticulo-punctate |
. |
| . |  |
Congo & Zaïre - latro |
| -- |  TL
1.0-1.2 mm; head 1.25 longer than wide; propodeum dorsum convex, teeth
feeble; petiole short and high; shiny except for dense, coarse
puncturation on propodeum; colour yellowish-brown, head and medial
gaster darker (close to erythraeus) |
Uganda - thoracicus |
|
subgenus Aeromyrma - based on Weber (1952) | -- |
| ¤ | Major only known | Botswana - africanus |
| ¤ | Major only known | Zaïre - petulcus |
| 7 | TL < 1 mm | 8 |
| -- | TL > 1 mm | 10 |
| 8 | Antennae 10-segmented | 9 |
| -- |  Antennae
9-segmented, head one-sixth longer than broad, scape attains posterior
fifth of head; postpetiole 1.5 times broader than long |
|
| . |  |
Guinea & Gabon - debilis |
| 9 | Mandibles 4-toothed; TL 0.9 mm; scape attaining posterior third of head; head no more than lightly sculptured; postpetiole almost 2 times broader than long (soldier antenna is 9-segmented) | Kenya - jeanneli |
| -- |  Mandibles 5-toothed; TL 0.8 mm; head except frons densely
reticulate; propodeal declivity with a translucent lamella on each
side, that dentate at both ends; postpetiole twice as broad as long;
colour yellow, appendages paler |
Ghana - vorax |
| 10 |  Totally
without eyes; TL 1.0-1.2; postpetiole 1.3 times broader than long; head
smooth and shiny |
South Africa - arnoldiellus |
| -- | Eyes present, even if atrophied | 11 |
| 11 | TL 1.1-1.2 mm | 12 |
| -- | TL 1.5 mm | 16 |
| 12 | Propodeum without spines | 13 |
| -- |  Propodeum
with distinct spines, TL 1.1 mm, HL 0.42 HW 0.31; colour brown |
Zaïre - acutus |
| 13 | Head near rectangular in full face view, with straight sides | 14 |
| -- | Head more ovate with convex sides | 15 |
| 14 |  Mandibles
4- or 5-toothed; TL 1.1-1.3 mm; scape attaining posterior quarter of
head; no propodeal lamellae; colour reddish-yellow, gaster more brown |
South Africa - semilaevis |
| -- |  Mandibles
5-toothed; TL 1.2 mm; head a little over 1.25 times longer than broad;
postpetiole almost 1.5 times broader than petiole; propodeum marginate;
almost unsculptured; colour yellow |
Zimbabwe - lucidus |
| 15 |  TL
1.2 mm; head 1.2 times longer than wide; petiole node pointed dorsally;
postpetiole 1.5 times broader than petiole; almost entirely shiny;
colour reddish-ochreous, mandibles and at least an area of the gaster
brownish |
Zambia - incertus |
| -- |  TL 1.2
mm; head 1.15 times longer than wide; petiole node low and rounded;
postpetiole 1.3 times broader than petiole; head with some
puncturation; mesopleurae, propodeum and pedicel finely
reticulo-punctate; colour dirty-yellow |
Mozambique - nanus |
| -- |  TL
1.1-1.2 mm; mandibles 4-toothed; propodeal dorsum flat, declivity
margined with a fine lamella; head mostly shiny, propodeum faintly
reticulate-punctate, rest shiny; colour pale yellowish-brown, antennae
and legs ochreus |
Zimbabwe - khamiensis |
| 16 |  TL
1.5 mm; head narrower; propodeum with very small tubercle at angle;
colour yellow with reddish tint |
South Africa - traegaordhi |
| -- | TL 1.5 mm; head 1.17 times longer than broad; generally smooth and shiny but mesonotum, propodeum and petiole finely reticulate-punctate; colour dull brownish-yellow, head darker, appendages and apex of gaster paler; robust | Uganda - ugandanus |
|
subgenus Aneleus | -- |
| ¤ | Queen only known | Angola - paetus |
| 17 | Propodeum with no more than short teeth | 18 |
| -- | Propodeum with long upper spines, lamellate margin and short lower teeth | 21 |
| 18 | TL < 1.2 mm | 19 |
| -- | TL > 1.2 mm | 20 |
| 19 |  TL
1.2 mm; head rectangular with straight sides; metanotal suture shallow;
propodeal teeth reduced to tubercles; densely puncturate but quite
shiny; yellow, |
Cameroun, CAR - diabolus |
| -- |  TL
1.0 mm; head only 1.14 times longer than wide, with markedly convex
sides and long frontal carinae; propodeal teeth short but acute |
Kenya - punctatus |
| 20 |  TL 1.8-2.0 mm; pedicel nodes especially petiole rounded in
profile; head slightly longer than wide, sides convex and posterior
angles sharp; mandible 5-toothed; propodeum with two small sharp spines
(as in soldier); sculpturation similar to soldier but head without
transverse rugae; sparse yellowish pilosity; colour testaceous red,
clypeus and mandible rust brown |
(? Nigeria - undetermined species) Fernando Po I. - menozzii |
| -- |  TL 1.5 mm; head elongate, sides moderately convex,
occipital margin concave and sharp; pronotum with sharply defined
margins; propodeum with triangular tooth on each side; petiole narrow
with post-petiole barely wider; colour reddish-yellow (note arnoldi
is TL 1.0-1.4 mm) |
. |
| . |  |
East & South Africa - perpusillus |
| 21 |  TL
ca 1.0-1.25 mm; (note no description ever made, thus based on soldier
and drawing) apparently pronotum with sharp straight anterior margin;
colour testaceous red |
Ghana & Guinea - silvestrii |
| -- |  TL 1.8-1.9 mm; antenna with a distinctive two-segmented
club, the penultimate segment cup or goblet shaped; mandible with
six-teeth but centre pair reduced, leaving two large apical and two
large distal teeth; pronotum with rounded anterior margin; propodeum
with strong superior spines, declivity with lamellate lateral
margination and lower teeth |
Possibly a separate genus Sporocleptes Arnold - 22 |
| 22 |  (description for nicotianae) TL 1.9 mm; colour
ochreous (darker in politus), gaster lighter |
Kenya & Zimbabwe - politus |
| -- |  Bernard
in genus Nimbamyrma; TL 1.8 mm; colour bright yellow |
Guinea - probable junior synonym of politus villiersi |
Species from West Africa listed only by code letters
 |
MYRMICINAE Introduction |
© 2007, 2008 - Brian Taylor CBiol FIBiol FRES 11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K. |
href="oligomyrmex.htm"