Adelomyrmex

Adelomyrmex includes some of the least known myrmicine ants, which are rare in insect collections. The queen was unknown to date in the New World, and the male was unknown to date in the World. Little of the way of life of the species is known. (Fernández 2003)

Identification
Fernández (2003) - Adelomyrmex is defined by at least three traits postulated to be synapomorphic, that establish the putative monophyly of this taxon.

(1) Clypeal structure: elevated medially, in form of a very narrow longitudinal platform, with sharply delimited lateral borders. From this median platform the clypeus is sloped laterally in form of a concavity each side, and in lateral view forms a ventral concavity. The anterior clypeal border, in the elevated portion, is formed in some taxa as a slightly or distinctly defined bidentate projection, the median clypeal teeth. The anterior clypeal margin possesses, in most species, a pair of teeth, one on each side of the median proyection, generally close and opposed to the teeth of the basal margin of mandibles, the lateral clypeal teeth.

(2) Number and disposition of the clypeal setae: one apical (sometimes replaced with a pair of apical setae), which is projected laterally, and two pairs of paracarinal setae, the first pair inserted near the lateral borders of the clypeal platform and the second laterally from the sides of the clypeus. The clypeal area possesses other setae, but in some species, number and conformation vary among the included species. The pattern of the clypeal setae (an apical and two paracarinal setae) is constant in all species studied.

(3) Mandibles with a tooth near the proximal quarter of the basal margin. In general it is followed by a hiatus or notch of variable size. In most of the species these teeth are (with the closed or almost closed mandibles) opposed to the teeth of the anterior clypeal margin (the lateral clypeal teeth). Additionally, the palpal formula is 2,2 or less.

The basal mandibular tooth isolates Adelomyrmex not only from its close relative, Baracidris, but from most other myrmicines (Perissomyrmex possesses teeth in the basal margin, but this is a very distant genus; Longino & Hartley, 1994). In some workers of Adelomyrmex tristani and Adelomyrmex silvestrii, this tooth is hardly noticed, but this may be interpreted as secondary reduction.

Fernández (2004) created a generic group consisting of Cryptomyrmex, Adelomyrmex and Baracidris that shared the following characters: With characters of solenopsidine tribe group (Bolton, 2003:57). Mandibles with four to seven teeth in the masticatory border (Fig. 4). Basal margin of mandibles simple to armed. Internal side of mandibles with a row of 2-3 to 5-6 hairs modified as lamelliform setae. Clypeus with median longitudinal plate, ridge or strip raised (Fig. 3). A median clypeal seta usually present. Palpal formula 2,2 or less. Antennae 12 segmented, with club 2-segmented. Propodeum angulated or armed with teeth. U-shaped sulcus in the basalmost portion of the first tergum. Monomorphic.

These three genera can be separated using the following key:

1

 * Mandibles with four teeth in the masticatory border; frontal area lacking; petiolar node low; Brazil and Paraguay . . . . . Cryptomyrmex 
 * Mandibles with 5-7 teeth in the masticatory border; frontal area present, reduced; petiolar node high (Fig. 2) . . . . . 2

2
return to couplet #1
 * Clypeal lateral teeth present; basal margin of mandible with teeth and notch; hypostomal teeth present, usually small; Neotropics, New Guinea, Fiji, Samoa and New Caledonia . . . . . Adelomyrmex
 * Clypeal lateral teeth absent; basal margin of mandible without teeth; hypostomal bridge without teeth; Africa . . . . . Baracidris

Distribution
Represented in the Neotropical Region by more than 20 species ranging collectively from northern México to southern Brazil and Paraguay, but absent from Chile, in the south, and from the West Indies, in the Caribbean Basin. The three species of the Old World inhabit islands (Fiji, Samoa and New Guinea) more or less near the Australian continent.

Species richness
Species richness by country based on regional taxon lists (countries with darker colours are more species-rich). View Data



Nomenclature

 *  ADELOMYRMEX [Myrmicinae: Adelomyrmecini]
 * Adelomyrmex Emery, 1897c: 590. Type-species: Adelomyrmex biroi, by monotypy.
 * Adelomyrmex senior synonym of Apsychomyrmex: Kempf, 1972a: 18.
 * Adelomyrmex senior synonym of Arctomyrmex: [Brown, 1973b: 178 (provisional synonym)]; Bolton, 1994: 106.
 * APSYCHOMYRMEX [junior synonym of Adelomyrmex]
 * Apsychomyrmex Wheeler, W.M. 1910a: 261. Type-species: Apsychomyrmex myops, by monotypy.
 * Apsychomyrmex junior synonym of Adelomyrmex: Kempf, 1972a: 18.
 * ARCTOMYRMEX [junior synonym of Adelomyrmex]
 * Arctomyrmex Mann, 1921: 457 [as subgenus of Adelomyrmex]. Type-species: Adelomyrmex (Arctomyrmex) hirsutus, by original designation.
 * Arctomyrmex junior synonym of Adelomyrmex: Bolton, 1994: 106.

Fernández 2003:

With character states of Adelomyrmex  genus-group (Genera included: Adelomyrmex and Baracidris).

Myrmicine ants with the following combination of characters:

Mandibles with 4 to 6 teeth in the masticatory margin.

Internal side of mandibles with a row of 2–3 to 5–6 hairs modified as lamelliform setae.

Clypeus with raised median longitudinal plate, ridge or strip.

Palpal formula 2,2 or less.

Frontal lobes not extending posteriorly as frontal carinae.

Antennal scrobes absent.

Antennae 12 segmented, with club 2-segmented.

Propodeum angulated or armed with teeth.

U-shaped sulcus in the basalmost portion of the first abdominal tergum.

Monomorphic.

Adelomyrmex  modified as follows. Worker Monomorphic, length from 1.80 to 4.2 mm. Body variously sculptured, from striate to coarsely reticulorugose. Erect or suberect setae on body, shorter and appressed on antennae and legs.

Head longer than wide, with posteriolateral corners rounded, and posterior margin slightly convex, flat, or slightly concave. Clypeus pronouncedly raised or elevated medially as a narrow longitudinal plate. Clypeus with median apical to slightly subapical seta long, projected laterad, also two lateral and two dorsal long setae posteriad apical seta. In side view clypeus concave ventrally. Anterior clypeal margin with two teeth near and opposing basal mandibular teeth. Frontal carinae distinct, closely approximated, with elongate and impressed area between them, extended to clypeal plate. Antennae 12 segmented, with 2-segmented club. Eyes relatively small, with 3 to 30 facets, situated slightly anteriad middle of head. Mandible with 4 to 7 teeth, with distinct tooth on basal margin, near to proximal quarter, in full face view opposing lateral clypeal teeth. Hypostomal tooth present, except in A. boltoni and A. longinodus. Palpal segments 2,2 or 1,1.

Promesonotum convex, without promesonotal suture. Metanotal groove distinct to indistinctly impressed. Propodeum with two spines. Propodeal spiracle round and at some distance from propodeal margin. Propodeal lobe subtriangular, rounded. Legs moderately stout, both middle and hind tibiae without spurs. Petiole distinct, campaniform to pedunculate; petiole with several ventral transverse rugae; postpetiole with conspicuous ventral transverse rugae (appearing in profile as toothlike projection).

Gaster oval (in one species with anterior angulate emarginations). Gaster smooth and shining to subopaque. Black to light brown in color. Sting large.

Queen: As worker, differing from workers in the normal myrmicine queenly traits. General body size as in worker in some species. Ocelli three; anterior ocelli in fossae. Eyes with more than 120 facets. Anterior promesonotal area smooth and shining, posterior area sculptured. Most of katepisternum smooth and shining. Wings as in figure 43, densely and finely setose.

Male (based on A. vaderi). With general traits of myrmicine males. Surface sculpture: promesonotum, major areas of sides of mesosoma and gaster smooth and shining, promesonotum with several punctures; head, mesonotum, propodeum (lateral and dorsal surfaces), petiole and postpetiole irregularly rugulose, postpetiole devoid of ventral transverse carinae. Anterior border of head, and propodeal, petiolar and postpetiolar dorsum with transverse trend.

Pilosity: body abundantly setose. Head, dorsum of mesosoma, petiole, postpetiole and gaster with conspicuous suberect long setae, those of petiole and postpetiole more appressed; in full face view, several long setae oriented outward and anteriorly from clypeal area; antennae densely covered with short, decumbent setae; numerous short, erect setae on eyes; mandibles with long curved setae directed outward and forward.

Head hemispheric. Clypeus medially protuberant, convex. Frontal carinae only partially covering antennal insertions. Eyes large, globose, with numerous facets (>30 in maximum diameter). Three ocelli, prominent and sphaerical. Antennae 13-segmented, flagellomeres increasing in size from scape to apex, without evident club; scape less curved than in workers, surpassing conspicuously border of vertex. Labrum exposed. Mandibles simple, pointed. Palpal formula (in situ) 2,2. Propodeal spiracle opening shifted posteriad and laterad. Propodeum without spines. Wings (Fig. 43) densely setose, but less than in females. Petiole subcampaniform, with node evenly meeting in rounded summit, postpetiole dome-shaped.