Phrynoponera

Five species are currently recognised in the genus, of which two, Phrynoponera bequaerti and Phrynoponera gabonensis, are widely distributed in the Afrotropical forest zone and are usually collected in leaf litter samples and pitfall traps. They nest in and under rotten wood, and sometimes directly in compacted soil. At least two species, gabonensis and Phrynoponera sveni, will also nest in upright or fallen termitaries, but are by no means common in such places (Dejean, et al. 1996, 1997). Phrynoponera species are not generally considered to be termitophagous, but in truth their actual diet remains unknown, so termites may form a part of it. Individuals are not particularly numerous in litter samples. Belshaw & Bolton (1994) recorded the two species that occur in Ghana (bequaerti, gabonensis) as comprising only 0.08% of individuals in the leaf litter ant fauna. Beyond these few facts, nothing is known of their biology.

Identification
Schmidt and Shattuck (2014) - Diagnostic morphological apomorphies of Phrynoponera workers include their posterodorsal propodeal spines and their squamiform, sweeping five-spined petiolar node. Propodeal spines or teeth also occur in Streblognathus, Pseudoneoponera bispinosa, and some species of Anochetus and Platythyrea, but these taxa all lack the unusual petiolar node of Phrynoponera, which is autapomorphic within Formicidae. Superficially, Phrynoponera most resembles Bothroponera (s.s.) and Pseudoneoponera, but it is readily separated from these genera by the combination of propodeal spines, unusual petiole structure, and weak gastral constriction. Bolton & Fisher (2008b) discuss additional diagnostic characters of the petiolar sternite and prora of Phrynoponera.

Distribution
Phrynoponera occurs in the forests of tropical Africa, with most species restricted to central Africa. Phrynoponera gabonensis has the widest range, occurring from Ivory Coast to Kenya and from Sudan to Angola. Phrynoponera pulchella, likely the sister to the rest of the genus, is known only from Kenya (Bolton & Fisher, 2008b).

Nomenclature

 *  PHRYNOPONERA [Ponerinae: Ponerini]
 * Phrynoponera Wheeler, W.M. 1920: 53. Type-species: Bothroponera gabonensis, by original designation.
 * Phrynoponera junior synonym of Pachycondyla: Snelling, R.R. 1981: 389.
 * Phrynoponera revived from synonymy: Bolton, 1994: 165.

Worker and Queen
Diagnosis of worker and queen (gyne)

Characters included in the diagnoses that are thought to be apomorphies are printed in italics.

Workers are known for all species; queens are known for all except Phrynoponera pulchella.

1 Mandible with 3–8 teeth; without a basal pit but with a weak basal groove.

2 Masticatory margin of mandible somewhat oblique; basalmost tooth at the rounded basal angle; mandible at most subtriangular, usually the basal and external margins roughly parallel.

3 Palp formula 4,4.

4 Frontal lobes large but not hypertrophied; median portion of clypeus extends back between them as a narrow triangle, to beyond the midlength of the lobes. Frontal lobes do not overhang anterior clypeal margin in full-face view.

5 Antenna with 12 segments, gradually incrassate apically but without a differentiated club.

6 Metanotal groove vestigial to absent (worker caste only).

7 Metapleural gland orifice simple, posterolateral.

8 Propodeum stoutly bispinose.

9 Propodeal spiracle with orifice slit-shaped.

10 Mesosternal and metasternal processes present.

11 Mesotibia and metatibia each with two spurs; the anterior spur on each small, simple to barbulate, the posterior spur pectinate.

12 Pretarsal claws small and simple.

13 Petiole surmounted by a high, stout scale that curves posteriorly over the base of the gaster and is armed dorsally with 5 long teeth or spines.

14 Petiole sternite appears simple in profile, with a short anteroventral process that is followed by a feebly sinuate to weakly convex simple plate.

15 Sternite of petiole in posterior view very complex, see discussion below.

16 Prora apparently absent but actually unusually modified and concealed, see discussion below.

17 Gastral segment 2 (abdominal segment IV) with differentiated but unusual presclerites, see discussion below.

18 Gastral tergite 2 (abdominal tergite IV) with stridulitrum usually absent, rarely vestigial.

19 Queen (gyne) only: alate when virgin, very similar in size to conspecific workers, varying from slightly larger to slightly smaller. Head with three ocelli present and mesosoma with full complement of flight sclerites. Mesopleuron with a weak transverse sulcus (absent in workers). Jugal lobe present on hindwing. In addition, workers of all known species have moderately large eyes (OI 19–27) and are strongly sculptured over the entire body. On the dorsal mesosoma the sculpture is coarse and usually consists of a coarse rugoreticulum, the spaces within the reticulum being depressed and concave. On the mesonotum the longitudinal rugose component may predominate, with anastomoses reduced or absent, so that the coarse sculpture has a longitudinal trend. Pilosity is always dense, with numerous conspicuous suberect to erect setae on all dorsal surfaces of the head and body, and also on the scapes and tibiae. In full-face view the sides of the head, from the posterior corner to the clypeus, have many outstanding short setae present. Colour is basically black throughout the genus, but with a marked tendency for certain areas to be brown, reddish brown, red, or even yellowish. Such lighter areas usually include the anterior portion of the head capsule, the antennae and mandibles, the legs, and often the apices of the gastral tergites and around the metapleural gland; the entire head capsule and much of the body may be reddish. All species show variation in the extent and intensity of such paler areas and colour variation in the known species has no taxonomic value.

Discussion of female characters.

Characters 8 and 13 above, in italics, are autapomorphic and together immediately differentiate Phrynoponera workers and queens from all other Ponerini. Characters 15 and 16 together are also highly diagnostic and are most probably also autapomorphic; some other characters have analogues developed convergently elsewhere in tribe Ponerini. Characters 1–19 together form an inclusive diagnosis that isolates Phrynoponera workers and queens from all other genera in the tribe.

6 The metanotal groove is absent in workers of most species. In some workers of Phrynoponera gabonensis, the dorsolateral ends of the metanotal groove are faintly visible.

13 Petiole structure is unique to the genus. The apical armament of the scale consists of a median spine or thick tooth, on each side of which is a slightly to markedly smaller spine or tooth, and outside that on each side is a longer, stouter spine. A longitudinal carina runs along the dorsal surface of the median spine.

14 Ventral surface of petiole also appears simple in ventral view: the anterior prominence is followed by a simple plate, without secondary carinae or teeth, though the surface of the sternite is sculptured. The posterior margin of the plate is simple, feebly convex to almost transverse.

15 When the petiole is disarticulated from the helcium, the petiole sternite, in posterior view, is seen as very complex. In the posterior third of its length the sternite bifurcates into an externally visible broad and concave ventral plate and a slightly shorter internally projecting sclerite that is completely concealed by the external plate in normal view. The internal sclerite terminates in a thickened concave arc that forms the actual articulation with the helcium and is homologous with the articulation seen almost everywhere else in the Ponerini. The ventral margin of the arc has a deep excision that is more than semicircular, and the apices of the excision are acute. Within Ponerini similar modifications are seen only in Asphinctopone and the species of Pachycondyla that formerly constituted the genus Brachyponera. In the latter, however, the lower plate is much less developed than in Phrynoponera and appears as a posteriorly directed tooth in profile that is considerably lower than, and does not overlap and conceal, the internal sclerite. This difference in form of development implies convergence rather than genuine homology. Asphinctopone is otherwise so different morphologically that convergent acquisition of this one character is likely.

16 Viewed externally the first gastral tergite appears to lack a prora, but disarticulation of the helcium from the petiole reveals that a uniquely specialised prora is present. Very reduced, it is inserted between, and appears fused to, the ventral apices of the helcium tergite. In effect this makes the helcium double-chambered, with the upper chamber floored by the helcium sternite and the lower chamber floored by the prora. In Ponerini a similar modification is observed only in the former Brachyponera species, but the degree of development is not so advanced.

17 Presclerites of the second gastral segment are present but usually concealed by the tergite and sternite of the first, so that the gaster usually appears small, roughly globular and compact. If the gaster is slightly distended the presclerites become apparent, but are not of the usual form. Instead of a girdling constriction between pre- and postsclerites, the postsclerites are instead depressed slightly below the level of the presclerites and are followed by a shallow concavity of the surface.

18 Most species show no trace of a stridulitrum but in one (Phrynoponera pulchella) there is a small, very roughly triangular, area anterodorsally on the presclerite of gastral tergite 2, at the midline, that has more regular transverse fine costulae than are visible on either side of it and behind it. This appears to represent the last vestige of a non-functional stridulitrum. The sculpture is much more crude and coarse, and far more widely spaced, than that seen on a genuine stridulitrum, and the area does not scatter white light, as is frequently seen with a functional stridulitrum.

The metacoxal cavities of all species except pulchella are atypical for Ponerini. Within the tribe the usual condition of the cuticular annulus around the metacoxal cavities is to have a narrow straight suture medially that traverses the annulus from the metacoxal cavity to the petiolar foramen, so that the cuticular apices of the annulus are transverse, not pointed; and this is the condition in pulchella. In all other Phrynoponera species each end of the annulus terminates in a blunt point and the two points are separated by a small gap. As pulchella also plesiomorphically retains a vestige of the stridulitrum, and all of its petiolar teeth are more similar in size, it seems likely that this species is sister to the remainder of the genus, that its metacoxal annulus represents the condition of the ancestral “normal Ponerini” and that the remaining species in the genus have secondarily evolved narrowly open metacoxal cavities.

Male
Known only for Phrynoponera gabonensis, previously undescribed.

1 Mandible very reduced, sublobate with a small apical tooth and a tiny basal denticle that is nothing more than an exaggeration of the basal angle.

2 Palp formula 6,4 (in situ count).

3 Frontal lobes absent; antennal sockets fully exposed.

4 Antenna with 13 segments, filiform.

5 Second funicular segment nearly three times longer than the short scape.

6 Eyes large, their inner margins shallowly evenly concave in the median third, not abruptly indented; ocelli prominent.

7 Notauli absent; mesoscutum with a short, narrowly triangular crest anteromedially.

8 Parapsidal grooves present.

9 Mesonotum with deep transverse groove between mesoscutum and mesoscutellum.

10 Epimeral lobe present, conspicuous.

11 Propodeal spiracle with orifice slit-shaped.

12 Mesotibia and metatibia each with two spurs, the anterior simple to barbulate, the posterior pectinate.

13 Pretarsal claws coarsely bifid apically on all legs; the two teeth approximately the same length, inner tooth always slightly more stout than the outer.

14 Hindwing with jugal lobe present.

15 Apex of petiole node with a coarse triangular median tooth, on each side of which is a flat lamella that is angulate at the outer corners.

16 Petiole in profile with an anteroventral tooth and a posteroventral long downcurved plate (appearing as a long curved tooth in absolute profile); posterior free margin of plate is broadly excised medially.

17 Prora apparently absent, modified as in worker and queen (see discussion below).

18 Gastral segment 2 (= abdominal segment IV) with a distinct girdling constriction between presclerites and postsclerites.

19 Gastral tergite 5 (= abdominal tergite VII) with a posterolaterally directed large, broadly triangular, prominence on each side; these prominences very densely setose.

20 Pygidium (= abdominal tergite VIII) with a long, strong, down-curved apical spine medially.

21 Hypopygium elongate-triangular.

22 Cerci (= pygostyles) present.

Discussion of male characters.

Characters 13, 15, 19, and the second half of 16, in italics, are autapomorphic for gabonensis males; their presence is considered to be of genus rank and therefore assumed to be universal within the genus. Character 17 is also highly diagnostic and most probably also autapomorphic. Characters 1–22 together form an inclusive diagnosis that isolates Phrynoponera males from all other genera in the tribe. As in the worker and queen some of the other characters are probably also apomorphies with convergent analogues elsewhere in Ponerini.

1 Reduced mandibles is a long-established apomorphy of male Ponerini (e.g. Bolton, 2003).

2 Bolton (2003) pointed out that in Ponerini dimorphism of palp formula between female castes and males was extremely common, with males characteristically having a higher PF count than females, suggesting this character may be an apomorphy of the tribe.

6 In many groups of Ponerini the inner margin of the eye is distinctly concave or suddenly indented in approximately its median third (e.g. Ogata, 1987; Yoshimura & Fisher, 2007).

13 A number of ponerine genera have the pretarsal claws with a preapical tooth in either the female castes, or in the male, or in both. Genera that have known males, and in which the females have simple claws and the males have toothed claws, include Diacamma, Psalidomyrmex, Streblognathus, some Plectroctena, some Odontomachus, and some groups within Pachycondyla. In all of these the preapical tooth is small compared to the apical and is some distance proximal of the apex, which is generally regarded as the plesiomorphic condition throughout the Formicidae. In Phrynoponera the preapical claws of the male are strongly bifid, with both components of about equal length; this condition is not otherwise known in the tribe. The condition is proposed as apomorphic for the genus.

15 The appearance of the dorsal apex of the petiole in the male is an obvious reduction of the condition universal in the female castes. The median tooth has a dorsal carina and a similar carina is visible on each side, close to the outer angle.

16 and 17 The ventral petiole and its articulation to the gaster are basically the same as in the female castes (see 15–16, above), but not as radically developed. The outer, posteroventral, plate of the petiole sternite is strongly curved downwards and has a V-shaped excision in its posterior margin, rather than being closely applied and convex apically as in the female castes. Because of this the inner, articulatory, sclerite of the sternite is visible in ventral view. The reduced prora, as in females, is inserted between the apices of the arched helcium tergite and is also visible in ventral view without disarticulation.

18 The girdling constriction between the presclerites and postsclerites of the second gastral segment is, in males, of the “normal ponerine” form and does not match the morphology of the female castes.

19 The presence of large, densely setose triangular prominences on the sides of the fifth gastral tergite is unique. Their function remains unknown though they are obviously sensory in nature.

The male morphology of Phrynoponera most closely resembles that of Pachycondyla (in the broad sense of Bolton, 1994, 1995; Yoshimura & Fisher, 2007), but in the latter several characters occur in a polymorphic condition. Characters common to Phrynoponera and Pachycondyla males include 1, 3, 4, 8, 9, 10, 12, 18, 20 and 22. Characters polymorphic in Pachycondyla males include 2, 6 (shape of inner margin of eye), 7, 11, 13 (claws simple or toothed, but not bifid) and 14. Characters 5 and 21 need further investigation through the tribe.

Worker
Schmidt and Shattuck (2014): Medium to large (TL 5–12 mm; Bolton & Fisher, 2008b) robust ants with the standard characters of Ponerini. Mandibles subtriangular, with a basal groove. Frontal lobes large. Eyes moderately large and placed anterior of head midline. Metanotal groove obsolete or vestigial dorsally. Propodeum broad dorsally, with a pair of sharp teeth on the posterodorsal margin. Propodeal spiracle a short slit. Metatibial spur formula (1s, 1p). Petiole squamiform, the scale curving posteriorly and armed with five sharp teeth posterodorsally. Gaster without a distinct girdling constriction between pre- and postsclerites of A4. Head and body coarsely sculptured, with abundant pilosity and no pubescence. Color variable.