Apomyrma, Brown, Gotwald Jr. & Levieux, 1971

Boudinot, Brendon E., 2015, Contributions to the knowledge of Formicidae (Hymenoptera, Aculeata): a new diagnosis of the family, the first global male-based key to subfamilies, and a treatment of early branching lineages, European Journal of Taxonomy 120, pp. 1-62 : 24-29

Apomyrma CD01

Figs 7C , 8–9

Non-type material examined (male)

DEMOCRATIC REPUBLIC OF THE CONGO, Bandundu: Wamba, Kikongo Mission, 4°15’S 17°10’E, 350–500 m elevation, Jul. 2008, Malaise trap ( T. Chapman), 20 Apr. 2008, forest Malaise trap (S.L. Heydon & S.E. Stevenson), 30 Mar.–5 Apr. 2006, Malaise trap in riparian forest (S.L. Heydon & S.E. Stevenson) and 24 Apr. 2006, Malaise trap in riparian forest (S.L. Heydon); Wamba, Nsheshe Forest NE of Kikongo Mission, 21–28 Jul. 2008, Malaise trap in primary forest ( T. Chapman). [Wamba is the name of the river running to the east of the georeference point.]

Male description

MEASUREMENTS (n=3). HL 0.36–0.41, HW1 0.32–0.38, HW2 0.45–0.51, MAL 0.06, MDL 0.03–0.04, SL 0.06–0.07, PDL 0.05–0.06, A3L 0.06–0.08, AAL 0.11–0.14, EL 0.22–0.26, EW 0.18–0.21, OOD 0.09–0.10, LOD 0.06–0.07, MOD 0.06–0.08, ML 0.78–0.95, MLL 0.22–0.25, MLW 0.17–0.20, MTL

0.46–0.57, MTW 0.33–0.40, PFL 0.29–0.36, MFL 0.30–0.37, PTH 0.13–0.16, PTL 0.12–0.16.

INDICES. CI 0.89–0.93, CS 0.34–0.40, SEI 356–427, SI 18.2–19.2, EI 77.4–82.5, EYE 118–120, MDI 8.2–10.5, OBI 70.4–74.6, OMI 3.71–4.50, MNI 2.05–2.14, MTI 126–144, FI 93.6–98.9, PTI 97.9– 109.1. Small, mesosoma bulky and elongate; wings situated in posterior half of mesosoma ( Fig. 8B ).

HEAD ( Fig. 8A ). In full-face view head slightly longer than broad excluding eyes, broader than long including eyes. Palpal formula 2,1; palps short, not reaching hypostomal margin. Stipes with carina along medial margin. Labrum extremely reduced, very narrow and weakly convex, glabrous; lacking dentiform setae; lateral margins nearly contacting medial mandibular base. Mandibles strongly reduced, nub-like, edentate; mandalus enlarged but still ringed by sclerite in dorsal view. Clypeus well-developed; anterior margin weakly emarginate; medial clypeal portion maximum anteroposterior length between 1.5–2 maximum antennal socket diameters; posterior clypeal margin extending slightly between antennal toruli. Supraclypeal area indistinct. Antennal toruli situated distant from anterior head margin; anterior tentorial pits located anterior to lateral torular arches. Frons and ocellar area bulging. Occipital carina absent, occiput obscured by vertex in full-face view. Compound eyes bulging; medial and posterior margins weakly convex; compound eye slightly narrower posteriorly than anteriorly. Ocelli small, situated distantly from compound eye. Hypostomal margin reduced, medial hypostoma narrowly carinate. Antenna 13-merous; scape overall smaller than pedicel; pedicel subspherical, slightly shorter than antennomere 3; funiculus filiform, not elongate, reaching propodeum when laid posteriorly against mesosoma.

MESOSOMA ( Fig. 8 B–C). Pronotal neck very short, discontinuous laterally with remainder of sclerite in dorsal view; pronotum weakly musculated, anteromedian face linear and appressed to mesoscutum; dorsoventral height of anteromedian pronotal face in profile view about ¼ x mesoscutum height in profile view; lateral pronotal face concave posterad procoxal insertion. Mesoscutum considerably longer than broad in dorsal view (length 1.26–1.42 x width); anterior and posterolateral areas not swollen. Notauli distinct, fine, not cross-ribbed; meeting or barely meeting at midlength, but not extending to transscutal line. Parapsidal lines slightly longer than half mesoscutum length, slightly divergent. Parascutal carinae fine, weakly sinuate, situated so low on mesoscutum that carinae completely obscured by wing base. Scutoscutellar sulcus deeply impressed dorsally, V-shaped. Axillae enlarged, meeting at body midline. Mesoscutellum at same height as mesoscutum, dorsal margin linear in profile view. Metascutellum small, convex, not produced. Metanotal trough deep, long, elliptical, broader anteriorly. Mesopectus lacking oblique sulcus; subalar furrow very large, about same size as petiole. Spiracular sclerite absent. Lower metapleural area offset by upper metapleural area by sulcus; upper metapleural area anteroposteriorly narrow, convex, sclerite thinned and differentiated from lower metapleuron, mesopectus, and propodeum. Metapleural gland orifice conspicuous, wide open, directed laterally, slightly posteriorly. Propodeum parabolic in profile view, dorsal face shorter than and continuous with posterior face; propodeal spiracle circular, small, situated anteroventrally. Propodeal lobe reduced to small tubercle with dorsal, dorsoventrally-oriented carina; petiolar presclerites visible in profile view, unobscured by propodeal lobe.

METASOMA ( Fig. 8C ). Petiole wedge-shaped, weakly nodiform in profile view; anteriormost portion of petiolar tergum not offset by carina; petiolar tergum overlapping sternum; anterodorsal petiolar face weakly concave, curving into shallow node in profile view; node with poorly-developed posterodorsal face; petiolar sternum ventral margin convex in profile view, sternum with symmetrical curving longitudinal carinae forming concentric long ellipses; petiolar sternum lacking process. Abdominal segment III similar in size, shape, and sculpture to segment IV; helcium infraaxial, broad, presternite not visible ventrad pretergite; prora absent, transverse sulcus ventrad helcial sternum absent (present in worker). Abdominal terga IV–VIII and sterna IV–IX normally developed, not reduced or obscured in situ. Abdominal sternum IX apical margin obtusely triangular, not pronged or toothed.

FOREWING ( Fig. 9A , see note below). Tegulum reduced, elliptical, much longer than broad. Wings hyaline, completely covered by fine setose layer. Pterostigma absent. Wing venation Ogata type IVa: one submarginal cell and marginal cell 1 closed, 1m-cu present, thus discal cell 1 closed. Costal vein tubular, contacting Rf distally. Cells clustered in basal half of wing, with only marginal cell extending into apical half. Rsf1 less than half length of Mf1; Rsf1 and Mf1 parallel. Rs+M sinuate (see note on wing venation below). 2r-rs slightly shorter than Mf1, directed posteroapically, oblique to long axis of wing. Rsf4–6 tubular, meeting Rf, enclosing marginal cell. Mf4–6 present, tubular for a short distance before disappearing. Crossvein cu-a tubular, situated distad Mf1. CuF slightly divergent with respect to Mf4–6. 1A extending distad 1m-cu but not enclosing subdiscal cell. Marginal and discal cells elongate; length of each cell considerably greater than half their width.

HINDWING ( Fig. 9B ). Venation reduced, only R+Rs tubular. Four hamuli present.

Genitalia ( Fig. 9 C–H). Pygostyles absent. Abdominal sternum IX hexagonal in outline; spiculum somewhat long, about four times longer than broad at base; anterior margins angle distinctly posterolaterally from spiculum; anterolateral margins weakly divergent; posterolateral margins extending to broadly rounded apex posteromedially. Anterolateral sternal corners hooked anteriorly. Cupula dorsal and ventral faces anteroposteriorly narrow; lateral face broad. Basimere ventromedially produced as lamina, concealing basivolsella in ventral view. Basimere and telomere continuous in profile view; telomere dorsoventrally narrow, dorsal telomeral margin concave, ventral margin convex, telomere weakly upturned, apex setose and evenly rounded. Basivolsella lateromedially narrow, oriented dorsoventrally; anterodorsal corner produced as dorsomedially-directed spur which abuts penisvalvar ventral margin base in situ; cuspis lobate, elongate, directed posterolaterad. Digitus elongate, arched, directed posteromesad, apex hooked. Penisvalvae dorsomedially fused from base to almost 3/4 ths their length, and fused anterodorsally with basimeres; valvura short, linear; valviceps dorsolateral face convex, lateral apodeme produced ventrolaterally, forming concave shell-like structure in which volsella may rest; ventral margin strongly concave, raised dorsally and only slightly differentiated from concave ventrolateral penisvalvar face; phallotreme situated apically, between dorsal penisvalvar margins where penisvalvar dorsal margins curve ventrally.

COLORATION. Body uniformly castaneous, legs yellowed.

SCULPTURATION. Body weakly sculptured, mostly smooth and shining except for the following features: head, mesonotum, metasoma posterad petiole, and legs covered with more-or-less even, somewhat dense piligerous punctures; subalar sulcus weakly longitudinally costulate.

SETATION. All setae short to very short; head setae head coarse, decumbent to erect, evenly spaced, apices slightly overlapping bases; mesoscutal setae similar in form and density to head, sparser mediad parascutal carinae; mesoscutellar setae somewhat longer and more dilute than mesoscutal setae, but otherwise similar, absent on lateral mesoscutellar face; metascutellum with few, coarse setae; pronotum bearing comparatively fine setae anterolaterally, otherwise glabrous; mesopectus with comparatively fine, long, and dilute setae; metapleuron and lateral propodeal face glabrous, posterior propodeal face with setae similar to mesoscutellum; propleural and procoxal setae similar to head setae on anterior surfaces; leg setae coarse, short, pale, appressed on most surfaces but decumbent to subdecumbent on ventral femoral faces; only petiolar node bearing coarse setae; metasoma posterad petiole with setation similar to head and mesoscutum.

Note

Interpretation of the abscissae enclosing submarginal cell 1 is ambiguous. The crossvein 1m-cu may be apically displaced, producing a second Rs+M abscissa which splits into Rsf2 and Mf2, or 1m-cu

may be unmoved and Rsf2 may be absent. Without a transitional series it is currently not possible to accurately determine these particular abscissal homologies, although the abscissa in question has a thyridium (weakening), suggesting that it is 2rs-m (the latter case).

Discussion

The species-level identification of the males described here is uncertain, as unpublished molecular work on Apomyrma has revealed more than one species in the genus (P.S. Ward, unpubl. data). The male described here, “ Apomyrma CD01”, differs from other male-based Apomyrma morphospecies by the following characters: head capsule in full-face view shorter, compound eyes more strongly protuberant; and ocelli large (equal in size to morphospecies Apomyrma CF01). The morphospecies probably differ in morphometrics, wing venation, and genitalic morphology, but these character systems were not evaluated as no physical specimens of other morphospecies were available. It may be the case that of the specific lineages of Apomyrma , the male of A. stygia will remain unknown until another nest collection is made.

A strong morphological case could be made to revive the Apomyrminae and remove Apomyrma from the Amblyoponinae . Published molecular studies, however, recover Apomyrma within or sister to the Amblyoponinae , but with weakly supported relationships with either the XMAS ( Brady et al. 2006; Moreau & Bell 2013) or the OCP clade ( Moreau et al. 2006; Rabeling et al. 2008). Given these results, Apomyrma is conservatively treated as an amblyoponine here, despite compelling morphological characters suggesting a relationship with the Leptanillinae , Opamyrma , and even Martialis (see “Shared apomorphies” section below). For further remarks on the similarities of Apomyrma to other taxa, see the Discussion section of the Martialis heureka species account below.

Figures

Fig. 7. A–B. Forewing. A. Ventral view, gyne. B. Dorsal view, male. C–D. Mesosoma, lateral view, male. E–F. Paramere, lateral view, male. — A. Aneuretus simoni (Sri Lanka, CASENT0172259, A. Nobile). B. Nylanderia vividula (U.S.A., CASENT0058918, A. Nobile). C. Apomyrma stygia (Central African Republic, CASENT0086073, E. Prado). D. Anochetus boltoni (Madagascar, CASENT0063847, A. Nobile). E. Dolichoderus validus (Costa Rica, INB0003662427, B. Boudinot). F. Formica pacifica (U.S.A., JTLC000006350, B. Boudinot). Scale bars: A–C, E–F = 0.5 mm, D = 1.0 mm.

Fig. 8. Apomyrma CD01, male, photomicrographs (CASENT0086073, E. Prado). A. Head, frontal view. B. Body, lateral view. C. Body, dorsal view. Scale bars: A = 0.2 mm, B–C = 0.5 mm.

Fig. 9. Apomyrma CD01, male, photomicrographs. A. Forewing. B. Hindwing. C. Abdominal sternum IX, ventral view. D. Genital capsule, dorsal view. E. Genital valves, slightly splayed and without cupula, ventral view. F. Genital capsule, lateral view. G. Volsella and paramere, mesal view. H. Penisvalva in situ, mesal view. Scale bars: A–B = 0.5 mm, C–H = 0.1 mm. Abbreviations: see Material and Methods