Apomyrma

This genus is nominally monotypic but unpublished molecular evidence suggests there is more than one species in this clade (see Apomyrma CD01). The original description (Brown et. al 1970) of the species Apomyrma stygia stated this ant likely lives an entirely subterranean existence, primarily inhabits tropical forests, and belongs to a guild of centipede feeding ants. It was also stated that "Apomyrma, like many other other subterranean predatory ponerines, moves deep (30 cm or more) into the soil during the dry season (October to April), but during the rainy season it comes up to within 10 cm of the surface."

Identification
In the field and with the naked eye resembles a small, slender, shining Stigmatomma. Possesses a pedunculate petiole with no differentiated postpetiole. Helium attached low down on the anterior face of abdominal segment 3 (see figure in the Nomenclature section).

Distribution
Boudinot (2015) - Afrotropical, confirmed from: Côte d’Ivoire, Ghana, Benin, Nigeria, Cameroon, Central African Republic, Democratic Republic of the Congo, and South Africa.

Biology
The few known nests of the single species of this genus were found in soil nests and contained less than 100 individuals.

Castes
The type species description notes there are small and large form workers, with the variation being found between nests. The former are ~ 2 mm in total length while the latter are ~3 mm in total length and are generally more robust.

Ergatoid queens were found in the nest of the type series.

Nomenclature

 *  APOMYRMA [Apomyrminae]
 * Apomyrma Brown, Gotwald & Lévieux, 1971: 259. Type-species: Apomyrma stygia, by original designation.
 * Apomyrma in Ponerinae, Amblyoponini: Brown, Gotwald & Lévieux, 1971: 273; Wheeler & Wheeler, 1985b: 256; Hölldobler & Wilson, 1990: 10.
 * Apomyrma in Ponerinae, Apomyrmini: Dlussky & Fedoseeva, 1988: 78 (misspelled as Aromyrmini).
 * Apomyrma in Leptanillinae, Apomyrmini: Bolton, 1990b: 280; Kugler, 1992: 106.
 * Apomyrma in Apomyrminae, Apomyrmini: Baroni Urbani, Bolton & Ward, 1992: 316; Bolton, 1994: 16; Bolton, 2003: 39; Fisher & Bolton, 2014: 200.
 * Apomyrma in Amblyoponinae: Saux, Fisher & Spicer, 2004: 465.

Apomorphies of Apomyrma
Boudinot (2015) - Note: Characters here indicated are apomorphic for the Formicidae generally, given Bolton’s (2003) synthesis of plesiomorphies and novel observations.

1. Raised clypeal disc between antennae lateromedially compressed, forming wedge-shaped process in anterolateral view, posterolateral clypeal margins distant from antennal toruli (female castes) (note 1). [Clypeal disc broad, uncompressed.]

2. Axillae enlarged, meeting medially (male). [Axillae small, not meeting medially.]

3. Transverse sulcus posterior to helcial sternite present (female castes). [Transverse sulcus posterior to helcial sternite absent.]

4. Abdominal segment III posttergites unfused (all castes).

5. Spiracles of abdominal segment III enlarged and situated at extreme anterior margin of tergum in profile view (female castes) (note 2). [Spiracle smaller, situated distant from anterior tergal margin in profile view.]

6. Penisvalvae dorsally fused for most of length, and anterodorsally fused with basimeres (male). [Penisvalvae unfused dorsally, unfused with basimere.]

7. Anterior base of penisvalvar lateral apodeme strongly produced laterally, forming a helmet- or cowry-like bulbous structure. [Lateral apodeme nearly flush with to slightly raised from valviceps.]

Notes on apomorphies

1. Clypeus also lateromedially compressed in Leptanilla. 2. Although adduced as the sole synapomorphy for Apomyrma + Leptanillinae by Bolton (1990a), this may be a convergence, as the third abdominal spiracle of Opamyrma is considerably posterior to the anterior tergal margin in profile view.

The infraaxial helcium of the worker and male may be apomorphic, depending on placement of the genus.

Worker
Worker: Habitus in life and to the naked eye much that of a very small, slender, shining Amblyopone. Also reminiscent of Leptanilla.

Head oblong, depressed, parallel-sided, with rounded corners (like that of many female pristocerine Bethylidae), anterior corners of head unarmed. Eyes and ocelli lacking. Antennae 12-segmented, scapes very short and clavate, funiculus robust, with an indistinct 4-merous club. Antennal sockets round, impressed, completely exposed, the frontal carinae extremely reduced and indistinguishably fused with the reduced median portion of the clypeus to produce a small, subtriangular tumulus or convex platform that trails a brief septum posteriad scarcely beyond the level of the posterior socket rims (see Fig. 5). Clypeus, except for the small raised median portion, impressed, very narrow and not distinctly demarcated behind, its anterior border shallowly but broadly concave, unarmed. The basal part of the labrum forms a straight line within the clypeal concavity, and bears a row (actually backed by a second row) of peg-like teeth that seem at first sight to spring from the clypeal margin. These teeth fill the narrow space between the clypeus and the normally closed mandible. Mandibles short, gently curved, and linear, with bidentate apex and a few blunt, spaced teeth on apical half of inner border. Labrum broader than long, .sides converging distad; apex broadly emarginate; extensor surface with two irregular rows of peg-like teeth (or modified hairs) on basal half. Maxilla simplified from form of Stigmatomma pallipes (see Gotwald, 1969), without galeal comb, and galeal crown smoothly continuing the dorsal galeal margin; maxillary palpus 2-segmented. Labium apparently without paraglossal lobes; setae of subglossal brushes tapered to apices; labial palpi 2-segmented.

Truncus (= alitrunk, = thorax + propodeum) long and slender, consisting of a convex, immarginate pronotum into which is flexibly fitted a slightly longer oblong portion consisting mainly of propodeum, meso- and metathorax; mesonotum reduced to a narrow, depressed transverse strip largely covered by posterior edge of pronotum except when pronotum is flexed downward. Propodeal dorsum almost flat (weakly convex), immarginate but with pleura perpendicular; declivity strongly convex, immarginate and unarmed, overhanging lower part and orifice. Bulla of metapleural gland conspicuously outlined through cuticle, subcircular; propodeal spiracle contiguous with it anteriad. Coxae nearly the same size (anterior coxa largest); femora short and strongly incrassate toward their middle; tarsi short, slender at base but gradually becoming thicker to near their apices. Tibial spurs 1, 2, 2, the middle and posterior legs each with one large, broadly pectinate inner spur and a smaller, more slender, sparsely pectinate outer one. Metatarsus of anterior legs strongly curved, opposing the large pectinate tibial spur; other metatarsi straight, weakly clavate. Tarsal claws small, slender, simple.

Petiole with a massive subcubical node, a brief, slender, but distinct anterior peduncle, and a very short posterior peduncle. Both anterior and posterior faces of the node are vertical, and the petiole is connected to the gaster only by the narrowly strangulated connection of the posterior petiolar peduncle to the short anterior peduncle of the first gastric (postpetiolar) segment. Postpetiole (first gastric segment true abdominal segment III) reduced in size, only slightly broader than petiole; much smaller than the following segment, and showing a very slight beginning of constriction from the latter (constriction a little more distinct in the queen). Sternum of postpetiole especially reduced, only weakly convex and with only a suggestion of bilateral anteroventral processes on either side of a shallow anteromedian impression. Second gastric (IV abdominal) segment the longest, widest and deepest of the gaster; larger than the remaining apical segments taken together; these taper to a rounded apex from which issues a very long, slender, curved sting. Postpetiolar tergum and the terga of all succeeding segments of gaster easily and cleanly separable from sterna.

Entire body shining, smooth, with abundant small, distinct, spaced punctures on dorsum of head, becoming fewer and smaller on truncus and remainder of body; legs and antennal funiculae becoming more densely and finely punctulate apicad; cervix and a few other areas on sides of truncus and node loosely reticulate. Entire body (except lower sides of truncus) and appendages covered densely (more sparsely on under.side of petiole and gaster) with short, fine, pointed hairs.

Color ferruginous yellow; mandibles and appendages lighter yellow.

Queen
alate: Like the worker in general form of body, but more robust overall. Eyes well-developed, pigmented and moderately convex, with about 10 facets across the greatest diameter, situated far back, at about the posterior quarter of the head length. Ocelli developed, situated between compound eyes. Pterothorax well developed but nearly flat, continuing the nearly straight (very feebly convex) dorsal profile of the truncus as seen from the side. Scutum, prescutellum (= axillary area) and scutellum all developed, flat, the scutum without recognizable notauli or parapsidal furrows. Wings delicate, hyaline, microtrichiate.

The second and third free abscissae of Rs are wanting, creating a large cubital cell; Mf4 is completely lacking, and there is even a small gap left at its former origin at the angle between Mf3 and r-m, so that the cubital cell is not completely closed at its posterodistal corner (Fig. 7). Rs narrowly recurved into costal margin about halfway between pterostigma and wing apex, thus enclosing a fairly long radial cell; except for Rs, apical half of wing membrane without veins. Hind wing narrow, acutely rounded, venation restricted to R + Sc, which fades out before reaching midwing; hamuli small and weak, 5 in number in the specimen counted; no anal lobe.

Petiolar node and gaster a little wider than in worker, and the incipient constriction between postpetiole and succeeding segment a bit more distinct. Form of body, sculpture, pilosity and color otherwise much as in worker (the pilosity may be slightly more abundant and a bit longer.)

Male
Boudinot (2015) - Male Apomyrma are recognizable by the combination of nub-like mandibles, anteriorly elongate mesosoma, reduced wing venation (marginal, costal, discal, basal, subbasal cells closed; subdiscal cell 1 open; submarginal 1 closed or open; pterostigma absent; 2r-rs situated in basal half of wing), and small, wedge-shaped petiole which is broadly and infraaxially attached to abdominal segment III.

1. Alate (Fig. 8B–C).

2. Mandalus somewhat enlarged, but clearly ringed by sclerotized mandibular cuticle in dorsal view (Fig. 8A).

3. Mandibles strongly reduced, nub-like, lacking teeth (Fig. 8A).

4. Labrum strongly reduced, subrectangular.

5. Palpal formula 2,1, palps strongly reduced in size.

6. Antenna 13-merous; funiculus filiform.

7. Occipital carina absent (Fig. 8B–C).

8. Eyes situated anteriorly, malar area visible in profile view (Fig. 8B).

9. Oblique mesopleural sulcus absent (Fig. 8B).

10. Subalar sulcus broadly enlarged, larger than lower metapleural area (Fig. 8B).

11. Epimeron narrow, lamellar (Fig. 8B).

12. Metapleural spiracular plate absent (Fig. 8B).

13. Mesoscutum anteriorly elongated, with concomitant elongation of lateral pronotal face (Fig. 8B–C).

14. Notauli fine, shallowly impressed, nearly meeting at midline (Fig. 8B–C).

15. Axillae enlarged, meeting medially (Fig. 8C).

16. Scutoscutellar sulcus exceedingly fine (Fig. 8C).

17. Metapleural gland orifice conspicuous (Fig. 8B).

18. Propodeum small, convex (Fig. 8B).

19. Propodeal spiracle small, circular, situated in anteroventral sector of lateral propodeal face (Fig. 8B).

20. Propodeal lobe absent (Fig. 8B).

21. Ventrolateral meso- and metapleural margins ecarinate (Fig. 8B).

22. Velum of calcar absent.

23. Forewing lacking membrane anterior to costal vein (Fig. 9A).

24. Forewing venation Ogata type IVa: Submarginal cell, marginal cell 1, and discal cell 1 closed; subdiscal cell 1 open (Fig. 9A).

25. Forewing costal vein present, reaching 2r-rs (Fig. 9A).

26. Hindwing venation reduced, only R+Rs tubular (Fig. 9B).

27. Jugal lobe absent (Fig. 9B).

28. Petiole subsessile, conical, broadening posteriorly; posterior face weak; anterior and posterior foramina oriented along main body axis (Fig. 8B).

29. Petiolar tergum lacking anterior parabolic carina (basipetiolar carina).

30. Subpetiolar process absent (Fig. 8B).

31. Helcium infraaxial (Fig. 8B), broad in dorsal view.

32. Prora of abdominal sternum III absent (Fig. 8B).

33. Abdominal segment III undifferentiated from IV (Fig. 8B).

34. Cinctus between abdominal segment IV pre- and postsclerites absent (Fig. 8B).

35. Abdominal tergum VIII posterior margin parabolic, unmodified (Fig. 8B).

36. Abdominal sternum VIII visible in situ.

37. Abdominal sternum IX unmodified; neither pronged nor toothed (Fig. 9C).