The Ants of Africa
SUBFAMILY FORMICINAE - Genus Polyrhachis subgenus Myrma
Contents - Formicinae - FORMICINAE Introduction

Genus Polyrhachis F.Smith (1857a: 58)

In Tribe CAMPONOTINI.

Diagnostic Features - Antennae 12-segmented, with the scapes inserted some distance behind the posterior clypeal margin. Eyes well developed. Mandibles usually with five, rarely four teeth. Pronotum armed with a pair of spines, teeth or tubercules; the propodeum usually similarly armed or with a pair of ridges, rarely with only a single transverse ridge or unarmed. Promesonotal suture usually present, development of the metanotal groove variable. Margination of the alitrunk variable, often present and complete but showing all stages through to a fully emarginate condition. Petiole usually with four but occasionally two or six spines or teeth of variable configuration. Acidopore not borne upon a conical projection of the hypopigium, usually concealed by the pygidium when not in use. Smith's (1857a) genus definition is at {original description}.

Fully revised by Bolton (1973b), all the species fall within the subgenus Myrma Billberg (1820: 104). This placement was supported by Dorow (1995a: 30). Bolton's full text can be found at - Bolton, B. 1973. The ant genus Polyrhachis F. Smith in the Ethiopian region (Hymenoptera: Formicidae). Bull. Brit. Mus. (Nat. Hist.) Entomol. 28: 285-369. View or download entire file (6.8M) .

Billberg, G.J. 1820. Enumeratio Insectorum in Museo G. J. Billberg. Stockhom. 138 pp - not listed in HNS
Dorow, W. H. O. 1995. Revision of the ant genus Polyrhachis Smith, 1857 (Hymenoptera: Formicidae: Formicinae) on subgenus levels with keys, checklist of species and bibliography. Cour. Forschungsinst. Senckenberg. 185, 1-113 - HNS8099

Santschi's (1939c) key to Pseudocrytomyrma species, termed by Bolton (1973b) as the revoili-complex, is at {original description}.

Radoskowsky (1881: 197) listed Polyrhachis setulosus F Smith from Angola, collected by Welwitsch. Bolton (1973: 352) reported neither he, nor, earlier, Wheeler (1922) could find any mention of this species in the Smith literature, let alone any description, so he regarded the name as a nomen nudum.

Bolton (1973a: 352) also noted that the F Smith (1858: 73) statement of Polyrhachis consimilis being from Sierra Leone was probably an error, as the only related species are known solely from the Indo-Australian Region.


{short description of image}Polyrhachis lacteipennis F Smith; recorded from Egypt east to the Indian sub-continent and Myanmar can be seen on this link.


Key to workers from Sub-Saharan Africa, developed in part from Bolton (1973b):

{short description of image}Queen only; TL 7-8 mm; photographs on species page
Cameroun - andrei
1 Clypeus with a shallow, rectangular lobe flanked by a pair of denticles or teeth; eyes situated well up on the head, usually not breaking the outline of the sides in full face view; alitrunk broadened and foreshortened, with a swollen appearance in dorsal view; pronotum always marginate, at least for part of its length, but either the mesonotum or propodeum or both not marginate; propodeum unarmed, the declivity extremely deep 2
-- Clypeus either arcuate and entire or with a truncated median lobe; eyes breaking the outline of the head, except when the eyes are flat; alitrunk without a foreshortened and swollen appearance; alitrunk usually either marginate or totally without lateral margination; if partially marginate then propodeum armed 6
2 Petiole armed with two spines or teeth 3
-- Petiole armed with four spines or teeth 4
3 {short description of image}TL 7.4-7.6 mm; propodeum without a posterior transverse margination separating the dorsum from the declivity; petiole dorsolaterally with two long spines, curved backwards and somewhat outwards at their apices, so that the whole petiole is lyre-shaped .
. Polyrhachis curta West Africa & Congo Basin - curta
-- {short description of image}TL 5.5-5.7 mm; propodeum with a weak posterior transverse margination separating the dorsum from the declivity. Petiole dorsolaterally with a pair of small triangular teeth .
. Polyrhachis lestoni Ghana and Congo Basin - lestoni
4 {Polyrhachis latharis dorsum}Propodeum marginate laterally and posteriorly, separating dorsum 5
-- {short description of image}TL 4.8 mm; propodeum not marginate, dorsum rounding into sides and declivity .
. Polyrhachis alexisi. Congo Basin - alexisi
5 {short description of image}TL 6.5-7.0 mm; in dorsal view sides of propodeum widening below lateral margins; sides of face concave .
. {Polyrhachis latharis} Ghana - latharis
-- {short description of image}TL 6.5 mm; propodeum not wider below lateral margins; sides of face straight .
. Polyrhachis limitis Congo Basin - limitis
. Clypeus either arcuate and entire or with a truncated median lobe; eyes breaking the outline of the head, except when the eyes are flat; alitrunk without a foreshortened and swollen appearance; alitrunk usually either marginate or totally without lateral margination; if partially marginate then propodeum armed .
6 Pronotum not at all marginate 7
-- Pronotum marginate at least for part of its length, present as a raised or projecting flange, a ridge or an acute angle separating the dorsum from the sides 17
7 {short description of image}TL 6.1 mm; eyes flat and somewhat sunk into the surface of the head; all surfaces with numerous erect hairs, pubescence greyish and densest on alitrunk
.
. {short description of image} Cameroun - platyomma
-- {Polyrhachis monista}Eyes convex, not sunk into the surface of the head 8
8 Metanotal groove broad and deeply impressed; propodeum armed with a pair of long upturned spines; petiole with four long back-curved spines; dorsum of alitrunk with numerous stout, usually yellow hairs 9
-- {short description of image}Metanotal groove weakly developed or absent. propodeum unarmed or with a pair of tubercles, teeth or ridges which are notably smaller than those of the pronotum; petiole with a dorsal pair of spines and a lateral pair of teeth or shorter spines; no or only fine hairs on the alitrunk dorsum 10
9 {short description of image}TL 5.5-6.4 mm; promesonotal suture broad and deeply impressed; propodeum without a median tuberculiform prominence between the spines .
. Polyrhachis monista West Africa & Congo Basin - monista
-- {short description of image}TL 4.8-5.6 mm; promesonotal suture narrow, not impressed. Propodeum with a median tubercular prominence between the spines .
. Polyrhachis spitteleri West Africa & Congo Basin - spitteleri
10 Antennal scapes or alitrunk dorsum or both with erect hairs; mesoscutellum not visible on alitrunk dorsum 11
--
{short description of image}TL 7.7-8.5 mm; antennal scapes and alitrunk dorsum without erect hairs; mesoscutellum visible on alitrunk dorsum South Africa - gamaii
11 Pronotal dorsum sculptured, armed with a pair of distinct spines 12
-- Pronotal dorsum smooth and polished, armed with a pair of small-minute teeth or tubercles 15
12 Propodeum armed posteriorly with a pair of transverse ridges separating the dorsum from the declivity 13
-- Propodeum armed posteriorly with a pair of short upcurved teeth, between which the dorsum curves into the declivity 14
13 {short description of image}TL 5.9 mm; median clypeal margin with anterior projecting lobe, slender; long scapes SI 181
.
. {short description of image} Congo Basin - volkarti
-- {short description of image}TL 5.9-6.1 mm; median clypeal margin arcuate and entire, stouter .
. Polyrhachis lanuginosa Congo Basin - lanuginosa
14 {short description of image}TL 6.1-6.5 mm; more than 30 erect hairs on each scape; dorsum of mesonotum and propodeum with rugose or rugo-reticulate sculpture; pubescence at least partly masking alitrunk sculpture.
.
. Polyrhachis revoili Eastern & southern Africa - revoili
-- {short description of image}TL 5.7-6.1 mm; scape with not more than 10 erect hairs; dorsum of mesonotum and propodeum sharply rugose. Possibly conspecific with revoili.
.
. Polyrhachis weissi West Africa & Congo Basin - weissi
Pronotal dorsum smooth and polished, armed with a pair of small-minute teeth or tubercles .
15 {short description of image}TL 5.7-5.9 mm; HL 1.30, HW 1.19, SL 1.54, PW 1.12; CI 91, SI 128
Head unsculptured, with a short longitudinal groove terminating in a pit-like depression posteriorly, close to the antennal insertion; dorsum of alitrunk with sutures, albeit poorly developed
.
. Polyrhachis braxa Ghana - braxa
--
Head weakly but distinctly sculptured
16
16 {short description of image}TL 5.2-5.6 mm, HL 1.20, HW 0.96, SL 1.38, PW 0.85; CI 80, SI 148
Head sculptured, but without a groove or pit, and alitrunk without sutures
.
. {Polyrhachis khepra} Ghana - khepra
-- Polyrhachis nsp CAR MorettoTL ca 5.3 mm, HL 1.20, HW 1.10, SL 1.35, PW 0.90; CI 85, SI 120
Head finely but distinctly sculptured, with a short longitudinal groove terminating in a pit-like depression posteriorly, close to the antennal insertion; dorsum of alitrunk with sutures, but not incised; anterior corners of pronotum with short but distinct teeth; mandibles mostly bright orange (others above completely dark)
Central African Republic - n sp CAR Moretto
return to couplet 4 Pronotum marginate at least for part of its length, present as a raised or projecting flange, a ridge or an acute angle separating the dorsum from the sides .
17 Metanotal groove represented only by a line or an indistinct scoring; metanotal groove never impressed, sometimes absent 18
-- Metanotal grove distinct, broad and always impressed 27
18 Antennal scapes with numerous erect hairs at right angles to the shaft 19
-- Antennal scapes without erect hairs 21
19 {short description of image}TL 6.8-7.6 mm; propodeum with a pair of transverse ridges separating the dorsum from the declivity, the ridges fail to meet medially and a small but distinct gap is present .
. Polyrhachis otleti West Africa & Congo Basin - otleti
-- Propodeum with a pair of teeth or minute tubercles, between which the dorsum curves into the declivity over its entire width 20
20 {short description of image}TL 7.2 mm; sculpturation of head between eye and frontal carina regularly and finely striato-rugose; dorsum of mesonotum laterally angled
. {Polyrhachis transiens} Uganda - transiens
-- {short description of image}TL 4.4-4.8 mm; sculpturation of head between eye and frontal carina an irregular rugo-reticulum; dorsum of mesonotum laterally rounded .
. {Polyrhachis regesa} Ghana - regesa
. Antennal scapes without erect hairs .
21 {short description of image}TL 6.2 mm; propodeum not marginate laterally, pronotum very weakly marginate for about half its length. sculpturation everywhere a fine reticulation or reticulate-puncturation Cameroun - aenescens
-- Propodeum marginate laterally; pronotum marginate throughout its length. Sculpturation of alitrunk a fine reticulate-puncturation overlaid by longitudinal rugae or a loose rugoreticulum 22
22 {Polyrhachis viscosa}Propodeum with a transverse ridge running between the spines of teeth and separating the dorsum from the declivity; ridge with a median tooth 23
-- {Polyrhachis nigrita}Propodeum without such a transverse ridge and no median tooth, petiole with a single pair of well-developed dorsolateral spines and no more than small teeth between on dorsum 26
23 Polyrhachis arnoldiTL 7.0-8.1 mm; gaster finely longitudinally striate .
. Polyrhachis arnoldi South Africa - arnoldi
-- Gaster finely reticulo-punctate 24
24 {short description of image}TL 5.9-7.6 mm; apex of scape dramatically broadened, concealing first segment of funiculus; eyes usually flat .
. {Polyrhachis viscosa} Sahel savannah - viscosa

Apex of scape not dramatically broadened, eyes convex 25
25 {short description of image}TL 6.1-7.0 mm; propodeum with a transverse ridge between the spines and but not raised medially into a tooth or tubercle; propodeal spines directed posterolaterally with only slight upcurve .
. Polyrhachis spinicola Mozambique - spinicola
-- {short description of image}TL 6.4-7.5 mm; propodeum with a transverse ridge between the spines and raised medially into a tooth or tubercle; propodeal spines curved upwards and outwards Tanzania south to South Africa - cubaensis
. Propodeum without a transverse ridge and no median tooth, petiole with a single pair of well-developed dorsolateral spines and no more than small teeth between on dorsum .
26 {short description of image}TL 7.0-8.9 mm; petiole with a single pair of well-developed spines at dorsolateral corners and small spines between .
. Polyrhachis nigrita West Africa & Congo Basin - nigrita
-- {short description of image}TL 6.7-7.3 mm; petiole with two pairs of well-developed spines, dorsal pair being longer .
. Polyrhachis durbanensis South Africa - durbanensis
return to couplet 17 Metanotal grove distinct, broad and always impressed .
27 Petiole with two spines 28
-- Petiole with more than two spines 29
28 {short description of image}TL 10.2-11.6 mm; petiolar spines subparallel and hooked apically, clypeus carinate, pubescence golden .
. {Polyrhachis laboriosa} West Africa & Congo Basin - laboriosa
-- {short description of image}TL 8.3-8.7 mm; petiolar spines divergent, curved but not hooked, clypeus smooth, pubescence not golden .
. Polyrhachis wellmani S Congo Basin & Angola - wellmani
. Petiole with more than two spines .
29 {short description of image}TL 4.7-6.7 mm; petiole with six spines or teeth the smallest pair situated behind the lateral pair of spines .
. {Polyrhachis decemdentata} West Africa & Congo Basin (Uganda forest) - decemdentata
-- Petiole with four spines or teeth 30
30 Pronotal dorsum without erect hairs 31
-- Pronotal dorsum with erect hairs 37
31 Dorsum of head with a pair of erect hairs situated on a level with the posterior margins of the eyes, or, if lost pits, marking location 32
-- Dorsum of head without erect hairs 33
32 {short description of image}TL 7.4-7.8 mm; anterior clypeal margin with a small shallow impression or notch medially; antennal scapes relatively extremely long; propodeal margins slightly arcuate and widening to position of teeth .
. {Polyrhachis decellei} Ghana - decellei
-- {short description of image}Anterior clypeal margin arcuate and entire; antennal scapes relatively much shorter; propodeal margins straight; entire body finely and densely reticulate, dully shining .
. {Polyrhachis esarata} Ghana - esarata
33 {short description of image}TL 8.6-9.1 mm; covered overall with very dense silvery pubescence; pronotum with long downcurved spines East & southern Africa - schlueteri
-- Pubescence usually sparse, if dense then not silvery; pronotal spines long or short but not downcurved 34
34 {short description of image}TL 6.8-7.6 mm; in posterior view the side of the head at the ventral margin of the eye projecting below the eye and forming a shield or blinker; in side view the ventral margin appearing concave, so that the eye is kidney-shaped; in full-face view the sides of the head in front of eyes noticeably concave .
. {Polyrhachis concava} West Africa & Congo Basin - concava
-- The side of the head not projecting; sides of head not noticeably concave in full-face view 35
35 {short description of image}TL < 6 mm; pronotal dorsum strongly concave transversely, lateral margins flanged; alitrunk from above and in profile more slender and relatively elongate
.
. {Polyrhachis aerope} Congo Basin - aerope
-- Pronotal dorsum no more than shallowly concave, lateral margins not flanged 36
36 {short description of image}TL 6.7-7.1 mm; sculpturation of head a fine dense reticulate-puncturation; on sides of head below and in front of the eye, and on the genae numerous distinct pits usually in groups of 3-4 .
. Polyrhachis alluaudi West Africa & Congo Basin - alluaudi
-- {short description of image}TL 5.0-5.4 mm; sculpturation of head a fine, dense reticulation; same sculpturation all over head .
. {Polyrhachis rufipalpis West Africa & Congo Basin - rufipalpis
return to couplet 30. Pronotal dorsum with erect hairs .
37 Lateral pair of petiole spines as long as, or longer than, the dorsal spines 38
-- {Polyrhachsi latispina}Lateral pair of petiole spines short, always shorter than the dorsal spines and may be reduced to a pair of short teeth 43
38 Antennal scapes with erect hairs 39
-- Antennal scapes without erect hairs 40
39 {short description of image}TL 5.4-5.9 mm, CI 79-86, SI 128-130; antennal scapes with numerous erect hairs projecting from the shaft; apical half of scape yellowish-brown; propodeum from above with straight sides
.
. {Polyrhachis asomaningi} West Africa & Congo Basin - asomaningi
-- Polyrhachis nsp Congo Sud 2007TL 5.3 mm, CI 94, SI 100; antennal scapes with few erect hairs; head with flatter occiput in full face view, lateral angles near square; propodeum from above with arcuate sides; median spines on petiole apparently much broader based; only extreme tip of funiculus lighter, rest black; head and alitrunk sculpturation much finer and more regular
Congo - dziodzio new species
40 {short description of image}TL 4.9-5.1 mm; first gastral tergite finely longitudinally striate-rugose, with numerous small punctures between the rugae .
. Polyrhachis phidias West Africa & Congo Basin - phidias
-- First gastral tergite finely superficially reticulate or reticulate-punctate 41
41
{short description of image}TL 5.6 mm; petiole with lateral spines enormously developed, dorsal pair reduced to spines .
. Polyrhachis cornuta Congo Basin - cornuta
-- Petiole with both pairs of spines similar; face with a short, longitudinal shallow groove terminating in a depression posteriorly, situated close to the outer margin of the antennal socket; 42
42 {Polyrhachis lauta}TL 5.5-6.2 mm; dorsum of propodeum extremely finely and longitudinally striate; erect hairs sparse but present on dorsum of head, pronotum and mesonotum
.
. {Polyrhachis lauta} West Africa & Congo Basin - lauta
-- {Polyrhachis fissa}TL 5.2-6.3 mm; dorsum of propodeum with quite fine rugose sculpture, occiput near sooth; gaster with quite abundant fine erect hairs; generally shinier than bequaerti
West Africa & Congo Basin (Uganda forest) - fissa
-- {Polyrhachis bequaerti}TL 5.5-6.2 mm; lateral alitrunk extremely finely and longitudinally striate; dorsum of pronotum and mesonotum with coarser longitudinal striations, also on occiput; dorsum of propodeum with quite coarse transverse striations; erect hairs sparse but present on dorsum of head, pronotum and mesonotum but very few and short on dorsal gaster
West Africa & Congo Basin - bequaerti
return to couplet 4. Lateral pair of petiole spines short, always shorter than the dorsal spines and may be reduced to a pair of short teeth .
43 {short description of image}TL 7.8-9.2 mm; propodeum not marginate. Entire body very deeply and regularly striate .
. Polyrhachis sulcata West Africa & Congo Basin - sulcata
-- Propodeum marginate 44
44 {short description of image}TL 11.3-13.2 mm; dorsum of alitrunk with no erect hairs except on pronotum; side of head without erect hairs; gaster highly polished .
. {short description of image} savannah areas of south Congo Basin & southern Africa - gagates
-- Dorsum of alitrunk with numerous erect hairs 45
45 Propodeal dorsum separated from declivity by an arched transverse ridge 46
-- Propodeal dorsum running smoothly into declivity 48
46 Pronotal spines no more than flattened triangular teeth 47
-- {Polyrhachis nsp CAR}TL 11.2-11.4 mm; pronotum with elongate widely divergent spines; head with fine dense spiculation; pubescence dense and very coarse on the alitrunk Congo Basin -  new species - ayousi
47 {short description of image} TL 9.4-11.2 mm;  head with fine dense longitudinal rugosity; pubescence sparse; numerous erect fine, whitish, hairs all over .
. Polyrhachis latispina Congo Basin - latispina
-- {Polyrhachis nsp CI Dupont}TL ca 9.4 mm, HW 1.79, HL 2.09, SL 1.98, PW 1.50; CI 86, SI 112
Distinctive flattened panel on side of gaster basal segment, the panel covered with dense fine longitudinal striae,
Ivory Coast -  new species - CI Dupont
return to couplet 44. Propodeal dorsum running smoothly into declivity .
48 Pubescence sparse, not hiding the sculpturation of the alitrunk or gaster, usually greyish in colour; narrow slender species 49
-- Pubescence abundant everywhere, hiding the sculpturation and usually with a golden brassy or bronze tinge. 50
. Pubescence sparse .
49 {short description of image}TL 9.3-13.7 mm; usually greyish in colour; narrow slender species; occiput always smoothy convex in full face view; scapes with quite abundant erect hairs
.
. {Polyrhachis schistacea} Pan-African savannah - schistacea
-- Polyrhachis straitiventrisTL 14.4 mm; occiput almost stright across; striations on the face, alitrunk dorsum and gaster well defined, although very fine and dense on the gaster; scapes and legs with very fine sculpturation; scapes with nil or very few erect hairs.; pubescence quite sparse on the alitrunk to almost nil on the gaster dorsum. Ivory Coast - striativentris
. Pubescence abundant everywhere .
50 {short description of image}TL 10.8-14.1 mm; alitrunk with marked lateral margination, especially the pronotum which usually is extended as a raised flange; the dorsal alitrunk somewhat concave between the margination; head with longitudinal striate-rugulation; eyes convex
. {Polyrhachis militaris} West Africa & Congo Basin - militaris
-- Polyrhachis medusaTL 12.6-14.4 mm; alitrunk without flanged margination and flat to weakly convex; overall sculpturation of fine superficial reticulation; eyes flat or nearly so East Africa - medusa
Contents Subfamily Formicinae
2007, 2008, 2009, 2010, 2011, 2013, 2014, 2015, 2017 - Brian Taylor CBiol FRSB FRES
11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K.

href="polyrhachis.htm"