Overview

Comprehensive Description

Adelomyrmex HNS

Basal border of mandibles with a tooth at or proximal to the midlength of the border.

Maxillary palp 1 - segmented (Gotwald, 1969).

Median portion of clypeus swept upwards into a strongly raised sharp-edged longitudinal platform which projects sharply forwards into a lobe; anterior clypeal margin sweeping downwards and outwards away from and behind the apex of this lobe.

Hairs present on dorsal surfaces of head and body.

Postpetiole not short-cylindrical in dorsal view, usually without a truncated ventral process.

Petiole usually high and narrow in profile, only rarely low.

Metapleural lobes small, separated from the propodeal spines above.

Range: Neotropics, New Guinea, Fiji, Samoa.

Among the Myrmicinae HNS of the Ethiopian zoogeographical region Baracidris HNS is unique in possessing 12 - segmented antennae with a 2 - segmented club. This character, coupled with the very closely approximated frontal lobes with the median clypeus narrowly inserted between them, the short 5 - dentate mandibles, reduced palp formula of 2, 2 and the shape of the pedicel segments, renders Baracidris HNS quickly recognizable. The key presented below will separate the myrmicine genera of the region which have a conspicuously 2 - segmented antennal club. Crematogaster HNS is included as a few species have such a club although the vast majority of species in this genus have the club 3 - segmented.

  • Bolton, B. (1981): A revision of six minor genera of Myrmicinae (Hymenoptera: Formicidae) in the Ethiopian zoogeographical region. Bulletin of the British Museum (Natural History) Entomology 43, 245-307: 253-253, URL:http://atbi.biosci.ohio-state.edu/HymOnline/reference-full.html?id=6438
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TAXONOMIC SYNOPSIS

Adelomyrmex HNS genus group. Neotropics, Samoa, Fiji, New Guinea, Central Africa.

Adelomyrmex betoi Fernandez HNS . México . NEW SPECIES .

A. biroi Emery HNS , 1897. New Guinea.

A. boltoni Fernandez HNS . Brazil and Paraguay. NEW SPECIES .

A. brevispinosus Fernandez HNS , 2003. México and Costa Rica

A. costatus Fernandez HNS . Colombia. NEW SPECIES .

A. cristiani Fernandez HNS . Colombia. NEW SPECIES .

A. foveolatus Fernandez HNS , 2003. Costa Rica.

A. grandis Fernandez HNS . Colombia. NEW SPECIES .

A. hirsutus Mann HNS , 1921. Fiji Islands.

A. laevigatus MacKay HNS , 2003. Costa Rica.

A. longinodus Fernandez & Brandao HNS . Brazil. NEW SPECIES .

A. longinoi Fernandez HNS . México and Costa Rica. NEW SPECIES .

A. mackayi Fernandez HNS . México . NEW SPECIES .

A. micans Fernandez HNS , 2003. México .

A. microps Fernandez HNS , 2003. Costa Rica.

A. minimus Fernandez HNS , 2003. Costa Rica.

A. myops (Wheeler HNS , 1910). Guatemala to Colombia.

A. robustus Fernandez HNS . México . NEW SPECIES .

A. samoanus Wilson & Taylor HNS , 1967. Samoa.

A. silvestrii (Menozzi HNS , 1931). Mesoamerica.

A. striatus Fernandez HNS . Brazil. NEW SPECIES .

A. tristani (Menozzi HNS , 1931). México to Colombia.

A. vaderi Fernandez HNS . Colombia. NEW SPECIES .

Baracidris meketra Bolton HNS , 1981. Nigeria.

B. pilosa Fernandez HNS . Kenya and Gabon. NEW SPECIES .

B. sitra Bolton HNS , 1981. Gabon.

  • Fernández, F. (2003): Revision of the myrmicine ants of the Adelomyrmex genus-group (Hymenoptera: Formicidae). Zootaxa 361, 1-52: 5-6, URL:http://www.antbase.org/ants/publications/20236/20236.pdf
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[[ Adelomyrmex HNS genus-group ]]

BIOGEOGRAPHICAL CONSIDERATIONS

The two genera of the Adelomyrmex HNS genus-group exhibit in the Southern Hemisphere a vicariant distribution pattern with Baracidris HNS confined to the Afrotropical part of the African continent, and with Adelomyrmex HNS being represented in New Guinea, the Western Pacific archipelagoes of Samoa and Fiji, and in the Neotropical Region (tropical South America and Middle America). Large gaps in range are a prominent feature of the distribution pattern.

Such vicariance suggests a group that originated in the Southern Hemisphere on the Gondwanian land mass before Africa became isolated in Lower Cretaceous time (some 135 to 125 MYA) (Storey, 1995; MacLoughlin, 2001). So, the ancestral stock of the extant genera of the group could have originated no later than that time, with initial differentiation of ancestral Baracidris HNS and ancestral Adelomyrmex HNS coinciding with separation of the West Gondwanian African continent from its principal counterpart, South America. Such timing predates the age of the earliest known ant fossils, indicating that the Formicidae is probably older than postulated previously.

The geographical range of ancestral Adelomyrmex HNS probably extended in later Cretaceous time from South America through East Gondwanaland (i.e., Antarctica + Australia + New Zealand). Probably events associated with climatic change (glaciation of Antarctica and drying of large parts of the Australian continent) were the driving forces in causing the present wide separation of elements of Adelomyrmex HNS , whose extant members seem to be adapted to tropical climate, and life in mesic habitats.

If, through unfavorable climatic changes, Adelomyrmex HNS experienced forced withdrawal from large parts of East Gondwanaland, in West Gondwanian South America, the opposite occurred, with range expansion into tropical Middle America, and extensive differentiation there (the A. tristani HNS species complex has there many populations isolated in valleys, from Panamá to México ).

In conclusion, the geographical distribution of Adelomyrmex HNS genus-group is an interesting biogeographic puzzle, the broad outlines of which have been addressed above. This subject will be addressed in more detail, in the prospective treatment of phylogenetic and chorological relationships of the group taxa.

  • Fernández, F. (2003): Revision of the myrmicine ants of the Adelomyrmex genus-group (Hymenoptera: Formicidae). Zootaxa 361, 1-52: 37-37, URL:http://www.antbase.org/ants/publications/20236/20236.pdf
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[[ Adelomyrmex HNS genus-group ]]

The genus Adelomyrmex HNS is known from the Neotropical and Australian-Pacific Regions with 12 described species (Bolton, 1995; Fernández & MacKay, 2003), while Baracidris (Bolton HNS , 1981) is a genus with 2 described species from Central and Western Africa. Bolton (1981) suggested that Baracidris HNS is close to Adelomyrmex HNS , based on the shared possession of antennae 12 segmented with 2 segmented club, and established the differences between both taxa. However, this suggested proximity was not reflected in the classification of the subfamily.

I propose that both genera form a monophyletic group and I redescribe Adelomyrmex HNS . A revision of all known species of the group is provided, including the description of new species.

TAXONOMIC HISTORY

The taxonomic history of the group is short. Emery (1897) proposed Adelomyrmex HNS to acommodate a single species, A. biroi HNS from New Guinea. Wheeler (1910) described the genus Apsychomyrmex HNS for a Mesoamerican species, A. myops HNS . Smith (1947) later reviewed this genus. Kempf (1972) placed Apsychomyrmex HNS as a junior synonym of Adelomyrmex HNS . Mann (1921) proposed Arctomyrmex HNS as a subgenus of Adelomyrmex HNS , a name synonymized under Adelomyrmex HNS by Bolton (1994). Bolton (1981) described Baracidris HNS and suggested its close relationship with Adelomyrmex HNS .

Forel (1917) placed Adelomyrmex HNS and Apsychomyrmex HNS in the tribe Leptothoracini HNS . Kempf (1972) put Adelomyrmex HNS in the tribe Leptothoracini HNS ; Hölldobler & Wilson (1990) left Adelomyrmex HNS and Baracidris HNS without tribal assignation, and Bolton (1994) placed both genera provisionally in Stenammini HNS .

  • Fernández, F. (2003): Revision of the myrmicine ants of the Adelomyrmex genus-group (Hymenoptera: Formicidae). Zootaxa 361, 1-52: 3-3, URL:http://www.antbase.org/ants/publications/20236/20236.pdf
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Genus Adelomyrmex Emery HNS

Adelomyrmex Emery HNS , 1897:590. Type species: Adelomyrmex biroi Emery HNS , 1897 (monobasic). Kempf, 1972:18 (Checklist of Neotropical species). Bolton, 1994:106 (Preliminary tribal assignment). Bolton, 1995:58 (World catalog).

Apsychomyrmex Wheeler HNS , 1910:261. Type species: Apsychomyrmex myops Wheeler HNS (monobasic). Emery, 1922:268; Smith, 1947: 468-473 (partial revision). Kempf, 1972:18 (as junior synonym of Adelomyrmex HNS ).

Arctomyrmex Mann HNS , 1921:457 (as subgenus of Adelomyrmex HNS (sensu lato)). Type species: Adelomyrmex hirsutus Mann HNS (monobasic). Brown, 1973:178 (provisional junior synonym of Adelomyrmex HNS ). Bolton 1994:106 (synonymy confirmed).

Adelomyrmex HNS 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.

Notes about synonymy and taxonomic history. The myrmicine ant genus Adelomyrmex HNS was previously known from the Neotropical and Oriental Regions, with 12 species ( Fernández & MacKay, 2003). The Neotropical species were formerly in the genus Apsychomyrmex HNS (described by Wheeler in 1910), with the sole species Apsychomyrmex myops HNS , based on a single worker from Guatemala. Menozzi (1931) described two new species, A. silvestrii HNS and A. tristani HNS , from Guatemala and Costa Rica respectively. Smith (1947) offered a synthesis of the systematics, way of life and geographical distribution of this genus, redescribing taxa and expanding the known ranges of some species. In this paper, Smith (1947) suggested the possibility of the presence of Apsychomyrmex HNS in México and South America. Kempf (1972) in his Neotropical catalogue, synonymized Apsychomyrmex HNS and Adelomyrmex HNS , following a suggestion of W.L. Brown, who did not provide formal justification for that proposal. Authors have followed Kempf's arrangement (i.e., Brown, 1973; Hölldobler & Wilson, 1990; Bolton, 1994, 1995). The Western Pacific islandic species Adelomyrmex hirsutus Mann HNS and A. samoanus Wilson & Taylor HNS were initially placed in the subgenus Arctomyrmex Mann HNS .

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

Diagnosis. Adelomyrmex HNS 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 (Figs. 9, 16, 22, 26, 47, 48, 54). From this median platform the clypeus is sloped laterally in form of a concavity each side, and in lateral view forms a ventral concavity (e.g. Fig. 15). The anterior clypeal border, in the elevated portion, is formed in some taxa as a slightly or distinctly defined bidentate projection (as in Fig. 9), 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 (e.g. Figs. 9, 22, 29), 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 (Figs. 16, 22). 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 (Figs. 22, 54). 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 (Fig. 59).

Description. With character states of Adelomyrmex HNS genus-group, 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 HNS and A. longinodus HNS . 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 (Fig. 42): 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 (previously unknown, based on A. vaderi HNS , Figs. 43, 44). 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.

Geographical distribution. Adelomyrmex HNS is represented in the Neotropical Region by 23 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. Initially the genus was divided in several species-groups (e.g. Fernández & MacKay, 2003; however, a recent cladistic analysis ( Fernández , unpublished) failed to support any of these groups. Then, for time being is not desirable to propose groups until more analysis can made.

Key to the species (workers):

1 Head and dorsum of promesonotum smooth and shining (as in Figs. 57, 58, 60) ... 2

- Head and promesonotum at least partly sculptured with striae, rugulae or punctures(as in Figs. 8, 11, 23, 28, 49, 56) .................................................................. 4

2(1) Petiole with node low (Figs. 57, 64, 65); propodeal spines large (Figs. 57, 64, 65); lateral clypeal teeth absent or not visible (Fig. 58) ................................................ 3

- Petiole with node high, shorter (as in Fig. 12); propodeal spines reduced to angles; lateral clypeal teeth present; México .............................................. A. micans HNS sp.n.

3(2) Propodeal dorsum and sides smooth; Brazil .............................. A. longinodus HNS sp.n.

- Propodeal dorsum and sides with longitudinal rugulae; Brazil and Paraguay ........ .......................................................................................................... A. boltoni HNS sp.n.

4(1) Most of promesonotum and first gastral tergum with coarse punctures; Old World ................................................................................................................................ 5

- Promesonotum at least partly with striae and/or rugulae; gaster without coarse punctures; New World .......................................................................................... 7

5(4) Propodeal spines large, stout (Fig. 66); New Guinea .................................. A. biroi HNS

- Propodeal spines small (Figs. 67, 68) .................................................................... 6

6(5) Head with longitudinal striation; eyes reduced to a few ommatidia; mesosoma in lateral view as in figure 68; Samoa ...................................................... A. samoanus HNS

- Head punctate; eyes reduced to dark spots; mesosoma as in figure 67; Fiji ........... ................................................................................................................ A. hirsutus HNS

7(4) Mesosomal dorsum with small to large areas smooth and shining (as in Figs. 49, 56) ............................................................................................................................... 8

- Mesosomal dorsum always sculpturated througout (Figs. 11, 17, 23, 28, 39, 40) .. ..............................................................................................................................12

8(7) Propodeal spines very short, wider than long (Fig. 45); promesonotum with small to median-sized, smooth and shining central area; México and Costa Rica............ ....................................................................................................... A. brevispinosus HNS

- Propodeal spines as long as wide or longer than wider (Fig. 51); promesonotum with a large smooth and shining area.................................................................... 9

9(8) Dorsum of head, between vertex and central area, smooth and shining and densely foveolated; Costa Rica........................................................................................ 10

- Dorsum of head never smooth and shining nor foveolate, instead reticulated or rugoreticulate .......................................................................................................11

10(9) Eyes with 7-8 ommatidia; HW> 0.50 mm; dark brown in color...... A. foveolatus HNS

- Eyes with one ommatidium; HW <0.50 mm; light brown in color...... A. minimus HNS

11(9) Most of side of pronotum smooth and shining (Fig. 51); hypostomal teeth large, stout (Fig. 53); eyes with 5 ommatidia; Costa Rica and Panamá ....... A. laevigatus HNS

- Sides of pronotum never with areas smooth and shining; hypostomal teeth never large or stout, eyes with two ommatida; Costa Rica............................... A. microps HNS

12(7) Mesosoma and gaster devoid of any kind of pilosity; body with bead-like carinae; postpetiole with a strong transverse carina; México ........................... A. betoi HNS sp.n.

- Mesosoma and gaster always hairy; carinae of body not bead-like; postpetiole without strong transverse carina.......................................................................... 13

13(12) Postpetiole posteriorly overhanging gaster (Figs 13, 18); in dorsal view, gaster distinctly emarginate at base, with humeral angles; Central America....... A. silvestrii HNS

- Postpetiole posteriorly not overhanging gaster (as in Figs. 12, 24); in dorsal view gaster without humeral angles..............................................................................14

14(13) Dorsum of mesosoma coarsely rugo-reticulate (Fig. 11).....................................15

- Dorsum of mesosoma with at least some central rugulae or costae more or less longitudinal (as in Figs. 23, 28), rarely with transverse striae (Fig. 39).............. 16

15(14) Propodeal spines pointed, higher than wide (Fig. 7); México to Colombia............ .................................................................................................................. A. myops HNS

- Propodeal spines low, wider than high; México ............................ A. mackayi HNS sp.n.

16(14) Lateral clypeal teeth very reduced, smaller than median clypeal teeth; HW 0.44 mm or less.............................................................................................................17

- Lateral clypeal teeth larger than median clypeal teeth; HW> 0.44 mm .............18

17(16) Eyes with six ommatidia; anterior margin of clypeal plate concave; HW> 0.42; Central Andes in Colombia .......................................................... A. cristiani HNS sp.n.

- Eyes with four ommatidia; anterior margin of clypeal plate straight; HW <0.42 mm; México to Costa Rica............................................................ A. longinoi HNS sp.n.

18(16) HW <0.82 mm ....................................................................................................19

- HW> 0.82 mm ....................................................................................................21

19(18) Promesonotum in lateral view notably convex (Figs. 35, 37); dorsum of promesonotum with regular longitudinal striation ......................................................... 20

- Promesonotum in lateral view feebly convex (Fig. 33); typical mesosomal dorsum as in figure 23, but some as in figures 39, 40; probably a complex of species; Méx- ico to Colombia ......................................................................................... A. tristani HNS

20(19) Promesonotum strongly convex anteriorly (Fig. 37); propodeal spines low, broader than higher (Fig. 37); Brazil ............................................. A. striatus HNS sp.n.

- Promesonotum evenly convex (Fig. 35); propodeal spines triangular (Fig. 35); Gorgona Island in SW Colombia ................................................... A. costatus HNS sp.n.

21(18) HW> 0.90 mm; SW Colombia ...................................................... A. grandis HNS sp.n.

- HW <0.90 mm .................................................................................................... 22

22(21) Promesonotum with abundant erect hairs (each about 0.14 mm); body brown with appendages light brown; Eastern Andes in Colombia ....................... A. vaderi HNS sp.n.

- Promesonotum with few to almost none erect hairs; head, mesosoma, petiole and postpetiole black with gaster and appendages dark brown; México ....................... ....................................................................................................... A. robustus HNS sp.n.

  • Fernández, F. (2003): Revision of the myrmicine ants of the Adelomyrmex genus-group (Hymenoptera: Formicidae). Zootaxa 361, 1-52: 8-13, URL:http://www.antbase.org/ants/publications/20236/20236.pdf
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Adelomyrmex HNS genus-group (Figs. 1-77)

Genera included: Adelomyrmex Emery HNS and Baracidris Bolton HNS .

Diagnosis. 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.

Discussion. Two features noted above and setation of the clypeus require some discussion. The most interesting character, evidently an autapomorphy for the group, is the presence of modified setae on the internal face of the mandibles. Most ants exhibit setae on the internal face of the mandibles, mainly in form of a parallel row near the masticatory margin (Figs. 1, 2, 3). This configuration is more or less general in ants, with some few setae scattered or diffuse ( Ponerinae , Pseudomyrmecinae HNS , Formicinae HNS , Myrmicinae HNS ). For Adelomyrmex HNS genus group, there is an important difference: these setae are lamelliform, transparent, varying in length and shape (Figs. 4, 5), from narrow and long to triangular or subtriangular. These lamelliform setae are very small and transparent, which makes their observation difficult with traditional magnification and light. Moreover, they need to be viewed from certain angles with particular light incidence. Also, in the ants normally mounted with mandibles closed, the internal setae are not visible. Only with the SEM pictures are the lamelliform setae easily visible (Figs. 4, 5) as a result of the gold coating.

The size and position of the lamellae suggest that these are modified setae, as stated below. These modified setae are very flexible, because in specimens with closed mandibles these structures bend on the integument. When a previously dry specimen is dampened and is mounted with open mandibles, the setae return to their erect position without breaking. The function of these structures is unknown, although they could be implicated in some type of sensorial specialization. Longino (1997) speculates about some kind of special prey for Adelomyrmex HNS , based on the clypeomandibular configuration (lateral clypeal teeth opposed to teeth in basal margin of mandible, Fig. 9). Unfortunately we do not know what these ants eat.

In some Adelomyrmex HNS species the modified setae are parallel to the occlusal border, with few or none near the basal tooth of the basal margin. In other species, seemingly, the setae are located more toward the basal margin of the mandible or are limited to two on the internal face of the basal margin, between the tooth of basal margin and the basal tooth of occlusal margin.

Although the U-shaped sulcus in the most basal portion of the first tergum (Fig. 6) may be a synapomorphy for the group (Bolton, pers. comm.), this structure is only shallowly impressed in some species. In workers of some other myrmicine genera (e.g. Myrmicaria HNS sp., Meranoplus mucronata HNS ) a similar structure is evident, and in the females of Solenopsidini HNS this sulcus is very deep. However, most myrmicines examined lack this sulcus(e.g. Myrmica HNS , Hylomyrma HNS , Monomorium HNS , Megalomyrmex HNS , Solenopsis HNS , Ochetomyrmex HNS , Tranopelta HNS , Pheidologeton HNS , Atopomyrmex HNS , Colobostruma HNS , Daceton HNS , Pheidole HNS , Aphaenogaster HNS ). I postulate that this trait has evolved more than once in Myrmicinae HNS .

The genus Adelomyrmex HNS exhibits an apical median seta on the clypeus, distinguished from the other clypeal setae, which I postulate as an apomorphic condition, but ancestral for the group. Nonetheless, the other genus of the group, Baracidris HNS , lacks this feature (at least the seta was not apparent at 200 X), which I believe to be a loss. Its absence could be a consequence of the reduction of the median clypeal fringe. However, if the clypeal configuration in Baracidris HNS and some Adelomyrmex HNS ( A. biroi HNS and A. hirsutus HNS ) is postulated to be ancestral, that is to say, the median portion of the clypeus represented merely by a narrow fringe, and the configuration in the species of the genus Adelomyrmex HNS is the derived condition, it can be thought that a central seta is an apomorphy for this genus alone, rather than for the Adelomyrmex HNS genus-group.

The Solenopsis HNS genus group possesses an apical clypeal seta projected forward (Bolton, 1987). However, this group exhibits other traits (number of antennomeres in antennae and antennal club) that excludes the possibility of the inclusion of Adelomyrmex HNS (and Baracidris HNS ) in the group. The median clypeal seta is also observed sporadically in some Stenammini HNS . Because the nearest tribe to Solenopsidini HNS seems to be Pheidologetonini HNS (Bolton, pers. comm.), which lacks the central clypeal seta, I postulate that the presence of a central seta could be a convergence among Solenopsidini HNS , Adelomyrmex HNS genus group and some Stenammini HNS .

How could a central seta have evolved in Adelomyrmex HNS ? In the ancestral situation we can imagine a continuous, flat clypeus with a row of apical setae of similar size (as in Myrmica HNS or Tetramorium HNS , Fig. 1). When the median bulge of the clypeus developed, some of these setae "migrated" to different positions, leaving one of them as central, accompanied at sides by paracarinal setae (Ettershank, 1966). In Solenopsidini HNS the clypeus does not present the degree of modifications as in Adelomyrmex HNS genus group; so the presence of a central seta must have an independent origin in this group. The same may be stated for those few Stenammini HNS that possess a central clypeal seta.

Geographical distribution. The range of the Adelomyrmex HNS genus-group includes the Neotropical and Afrotropical Regions, New Guinea, toward the eastern end of the Oriental Region, and the Samoan and Fijian archipelagoes in Oceania. See "Biogeographical Considerations ", below.

Key to genera of Adelomyrmex HNS genus-group

1 Basal border of mandible with tooth (as in Fig. 54); apical clypeal seta usually present (as in Fig. 9) and hypostomal bridge with median tooth as in (Fig. 29) or petiolar node low, poorly differentiated (Figs. 64, 65); Neotropics, New Guinea, Fiji, Samoa .......... ...................................................................................................... Adelomyrmex Emery HNS

- Basal border of mandible unarmed (Fig. 69); apical clypeal seta absent or not noticeable(Fig. 69); hypostomal bridge simple; node of petiole high (Fig. 69); West and Central Africa.................................................................................... Baracidris Bolton HNS

  • Fernández, F. (2003): Revision of the myrmicine ants of the Adelomyrmex genus-group (Hymenoptera: Formicidae). Zootaxa 361, 1-52: 6-8, URL:http://www.antbase.org/ants/publications/20236/20236.pdf
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Physical Description

Diagnostic Description

BIOGEOGRAPHICAL CONSIDERATIONS

 

The two genera of the Adelomyrmex genus-group exhibit in the Southern Hemisphere a vicariant distribution pattern with Baracidris confined to the Afrotropical part of the African continent, and with Adelomyrmex being represented in New Guinea, the Western Pacific archipelagoes of Samoa and Fiji, and in the Neotropical Region (tropical South America and Middle America). Large gaps in range are a prominent feature of the distribution pattern.

 

Such vicariance suggests a group that originated in the Southern Hemisphere on the Gondwanian land mass before Africa became isolated in Lower Cretaceous time (some 135 to 125 MYA) (Storey, 1995; MacLoughlin, 2001). So, the ancestral stock of the extant genera of the group could have originated no later than that time, with initial differentiation of ancestral Baracidris and ancestral Adelomyrmex coinciding with separation of the West Gondwanian African continent from its principal counterpart, South America. Such timing predates the age of the earliest known ant fossils, indicating that the Formicidae is probably older than postulated previously.

 

The geographical range of ancestral Adelomyrmex probably extended in later Cretaceous time from South America through East Gondwanaland (i.e., Antarctica + Australia + New Zealand). Probably events associated with climatic change (glaciation of Antarctica and drying of large parts of the Australian continent) were the driving forces in causing the present wide separation of elements of Adelomyrmex , whose extant members seem to be adapted to tropical climate, and life in mesic habitats.

 

If, through unfavorable climatic changes, Adelomyrmex experienced forced withdrawal from large parts of East Gondwanaland, in West Gondwanian South America, the opposite occurred, with range expansion into tropical Middle America, and extensive differentiation there (the A. tristani species complex has there many populations isolated in valleys, from Panamá to México ).

 

In conclusion, the geographical distribution of Adelomyrmex genus-group is an interesting biogeographic puzzle, the broad outlines of which have been addressed above. This subject will be addressed in more detail, in the prospective treatment of phylogenetic and chorological relationships of the group taxa.

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Adelomyrmex Emery , 1897:590. Type species: Adelomyrmex biroi Emery , 1897 (monobasic). Kempf, 1972:18 (Checklist of Neotropical species). Bolton, 1994:106 (Preliminary tribal assignment). Bolton, 1995:58 (World catalog).

 

Apsychomyrmex Wheeler , 1910:261. Type species: Apsychomyrmex myops Wheeler (monobasic). Emery, 1922:268; Smith, 1947: 468-473 (partial revision). Kempf, 1972:18 (as junior synonym of Adelomyrmex ).

 

Arctomyrmex Mann , 1921:457 (as subgenus of Adelomyrmex (sensu lato)). Type species: Adelomyrmex hirsutus Mann (monobasic). Brown, 1973:178 (provisional junior synonym of Adelomyrmex ). Bolton 1994:106 (synonymy confirmed).

 

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.

 

Notes about synonymy and taxonomic history. The myrmicine ant genus Adelomyrmex was previously known from the Neotropical and Oriental Regions, with 12 species ( Fernández & MacKay, 2003). The Neotropical species were formerly in the genus Apsychomyrmex (described by Wheeler in 1910), with the sole species Apsychomyrmex myops , based on a single worker from Guatemala. Menozzi (1931) described two new species, A. silvestrii and A. tristani , from Guatemala and Costa Rica respectively. Smith (1947) offered a synthesis of the systematics, way of life and geographical distribution of this genus, redescribing taxa and expanding the known ranges of some species. In this paper, Smith (1947) suggested the possibility of the presence of Apsychomyrmex in México and South America. Kempf (1972) in his Neotropical catalogue, synonymized Apsychomyrmex and Adelomyrmex , following a suggestion of W.L. Brown, who did not provide formal justification for that proposal. Authors have followed Kempf's arrangement (i.e., Brown, 1973; Hölldobler & Wilson, 1990; Bolton, 1994, 1995). The Western Pacific islandic species Adelomyrmex hirsutus Mann and A. samoanus Wilson & Taylor were initially placed in the subgenus Arctomyrmex Mann .

 

Recognition. 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 A. tristani and A. silvestrii , this tooth is hardly noticed, but this may be interpreted as secondary reduction.

 

Diagnosis. 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 (Figs. 9, 16, 22, 26, 47, 48, 54). From this median platform the clypeus is sloped laterally in form of a concavity each side, and in lateral view forms a ventral concavity (e.g. Fig. 15). The anterior clypeal border, in the elevated portion, is formed in some taxa as a slightly or distinctly defined bidentate projection (as in Fig. 9), 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 (e.g. Figs. 9, 22, 29), 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 (Figs. 16, 22). 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 (Figs. 22, 54). 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 (Fig. 59).

 

Description. With character states of Adelomyrmex genus-group, 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 (Fig. 42): 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 (previously unknown, based on A. vaderi , Figs. 43, 44). 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.

 

Geographical distribution. Adelomyrmex is represented in the Neotropical Region by 23 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. Initially the genus was divided in several species-groups (e.g. Fernández & MacKay, 2003; however, a recent cladistic analysis ( Fernández , unpublished) failed to support any of these groups. Then, for time being is not desirable to propose groups until more analysis can made.

 

Key to the species (workers):

 

1 Head and dorsum of promesonotum smooth and shining (as in Figs. 57, 58, 60) ... 2

 

- Head and promesonotum at least partly sculptured with striae, rugulae or punctures(as in Figs. 8, 11, 23, 28, 49, 56) .................................................................. 4

 

2(1) Petiole with node low (Figs. 57, 64, 65); propodeal spines large (Figs. 57, 64, 65); lateral clypeal teeth absent or not visible (Fig. 58) ................................................ 3

 

- Petiole with node high, shorter (as in Fig. 12); propodeal spines reduced to angles; lateral clypeal teeth present; México .............................................. A. micanssp.n.

 

3(2) Propodeal dorsum and sides smooth; Brazil .............................. A. longinodussp.n.

 

- Propodeal dorsum and sides with longitudinal rugulae; Brazil and Paraguay ........ .......................................................................................................... A. boltonisp.n.

 

4(1) Most of promesonotum and first gastral tergum with coarse punctures; Old World ................................................................................................................................ 5

 

- Promesonotum at least partly with striae and/or rugulae; gaster without coarse punctures; New World .......................................................................................... 7

 

5(4) Propodeal spines large, stout (Fig. 66); New Guinea .................................. A. biroi

 

- Propodeal spines small (Figs. 67, 68) .................................................................... 6

 

6(5) Head with longitudinal striation; eyes reduced to a few ommatidia; mesosoma in lateral view as in figure 68; Samoa ...................................................... A. samoanus

 

- Head punctate; eyes reduced to dark spots; mesosoma as in figure 67; Fiji ........... ................................................................................................................ A. hirsutus

 

7(4) Mesosomal dorsum with small to large areas smooth and shining (as in Figs. 49, 56) ............................................................................................................................... 8

 

- Mesosomal dorsum always sculpturated througout (Figs. 11, 17, 23, 28, 39, 40) .. ..............................................................................................................................12

 

8(7) Propodeal spines very short, wider than long (Fig. 45); promesonotum with small to median-sized, smooth and shining central area; México and Costa Rica............ ....................................................................................................... A. brevispinosus

 

- Propodeal spines as long as wide or longer than wider (Fig. 51); promesonotum with a large smooth and shining area.................................................................... 9

 

9(8) Dorsum of head, between vertex and central area, smooth and shining and densely foveolated; Costa Rica........................................................................................ 10

 

- Dorsum of head never smooth and shining nor foveolate, instead reticulated or rugoreticulate .......................................................................................................11

 

10(9) Eyes with 7-8 ommatidia; HW> 0.50 mm; dark brown in color...... A. foveolatus

 

- Eyes with one ommatidium; HW <0.50 mm; light brown in color...... A. minimus

 

11(9) Most of side of pronotum smooth and shining (Fig. 51); hypostomal teeth large, stout (Fig. 53); eyes with 5 ommatidia; Costa Rica and Panamá ....... A. laevigatus

 

- Sides of pronotum never with areas smooth and shining; hypostomal teeth never large or stout, eyes with two ommatida; Costa Rica............................... A. microps

 

12(7) Mesosoma and gaster devoid of any kind of pilosity; body with bead-like carinae; postpetiole with a strong transverse carina; México ........................... A. betoisp.n.

 

- Mesosoma and gaster always hairy; carinae of body not bead-like; postpetiole without strong transverse carina.......................................................................... 13

 

13(12) Postpetiole posteriorly overhanging gaster (Figs 13, 18); in dorsal view, gaster distinctly emarginate at base, with humeral angles; Central America....... A. silvestrii

 

- Postpetiole posteriorly not overhanging gaster (as in Figs. 12, 24); in dorsal view gaster without humeral angles..............................................................................14

 

14(13) Dorsum of mesosoma coarsely rugo-reticulate (Fig. 11).....................................15

 

- Dorsum of mesosoma with at least some central rugulae or costae more or less longitudinal (as in Figs. 23, 28), rarely with transverse striae (Fig. 39).............. 16

 

15(14) Propodeal spines pointed, higher than wide (Fig. 7); México to Colombia............ .................................................................................................................. A. myops

 

- Propodeal spines low, wider than high; México ............................ A. mackayisp.n.

 

16(14) Lateral clypeal teeth very reduced, smaller than median clypeal teeth; HW 0.44 mm or less.............................................................................................................17

 

- Lateral clypeal teeth larger than median clypeal teeth; HW> 0.44 mm .............18

 

17(16) Eyes with six ommatidia; anterior margin of clypeal plate concave; HW> 0.42; Central Andes in Colombia .......................................................... A. cristianisp.n.

 

- Eyes with four ommatidia; anterior margin of clypeal plate straight; HW <0.42 mm; México to Costa Rica............................................................ A. longinoisp.n.

 

18(16) HW <0.82 mm ....................................................................................................19

 

- HW> 0.82 mm ....................................................................................................21

 

19(18) Promesonotum in lateral view notably convex (Figs. 35, 37); dorsum of promesonotum with regular longitudinal striation ......................................................... 20

 

- Promesonotum in lateral view feebly convex (Fig. 33); typical mesosomal dorsum as in figure 23, but some as in figures 39, 40; probably a complex of species; Méx- ico to Colombia ......................................................................................... A. tristani

 

20(19) Promesonotum strongly convex anteriorly (Fig. 37); propodeal spines low, broader than higher (Fig. 37); Brazil ............................................. A. striatussp.n.

 

- Promesonotum evenly convex (Fig. 35); propodeal spines triangular (Fig. 35); Gorgona Island in SW Colombia ................................................... A. costatussp.n.

 

21(18) HW> 0.90 mm; SW Colombia ...................................................... A. grandissp.n.

 

- HW <0.90 mm .................................................................................................... 22

 

22(21) Promesonotum with abundant erect hairs (each about 0.14 mm); body brown with appendages light brown; Eastern Andes in Colombia ....................... A. vaderisp.n.

 

- Promesonotum with few to almost none erect hairs; head, mesosoma, petiole and postpetiole black with gaster and appendages dark brown; México ....................... ....................................................................................................... A. robustussp.n.

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Diagnosis. 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.

 

Discussion. Two features noted above and setation of the clypeus require some discussion. The most interesting character, evidently an autapomorphy for the group, is the presence of modified setae on the internal face of the mandibles. Most ants exhibit setae on the internal face of the mandibles, mainly in form of a parallel row near the masticatory margin (Figs. 1, 2, 3). This configuration is more or less general in ants, with some few setae scattered or diffuse ( Ponerinae , Pseudomyrmecinae , Formicinae , Myrmicinae ). For Adelomyrmex genus group, there is an important difference: these setae are lamelliform, transparent, varying in length and shape (Figs. 4, 5), from narrow and long to triangular or subtriangular. These lamelliform setae are very small and transparent, which makes their observation difficult with traditional magnification and light. Moreover, they need to be viewed from certain angles with particular light incidence. Also, in the ants normally mounted with mandibles closed, the internal setae are not visible. Only with the SEM pictures are the lamelliform setae easily visible (Figs. 4, 5) as a result of the gold coating.

 

The size and position of the lamellae suggest that these are modified setae, as stated below. These modified setae are very flexible, because in specimens with closed mandibles these structures bend on the integument. When a previously dry specimen is dampened and is mounted with open mandibles, the setae return to their erect position without breaking. The function of these structures is unknown, although they could be implicated in some type of sensorial specialization. Longino (1997) speculates about some kind of special prey for Adelomyrmex , based on the clypeomandibular configuration (lateral clypeal teeth opposed to teeth in basal margin of mandible, Fig. 9). Unfortunately we do not know what these ants eat.

 

In some Adelomyrmex species the modified setae are parallel to the occlusal border, with few or none near the basal tooth of the basal margin. In other species, seemingly, the setae are located more toward the basal margin of the mandible or are limited to two on the internal face of the basal margin, between the tooth of basal margin and the basal tooth of occlusal margin.

 

Although the U-shaped sulcus in the most basal portion of the first tergum (Fig. 6) may be a synapomorphy for the group (Bolton, pers. comm.), this structure is only shallowly impressed in some species. In workers of some other myrmicine genera (e.g. Myrmicaria sp., Meranoplus mucronata ) a similar structure is evident, and in the females of Solenopsidini this sulcus is very deep. However, most myrmicines examined lack this sulcus(e.g. Myrmica , Hylomyrma , Monomorium , Megalomyrmex , Solenopsis , Ochetomyrmex , Tranopelta , Pheidologeton , Atopomyrmex , Colobostruma , Daceton , Pheidole , Aphaenogaster ). I postulate that this trait has evolved more than once in Myrmicinae .

 

The genus Adelomyrmex exhibits an apical median seta on the clypeus, distinguished from the other clypeal setae, which I postulate as an apomorphic condition, but ancestral for the group. Nonetheless, the other genus of the group, Baracidris , lacks this feature (at least the seta was not apparent at 200 X), which I believe to be a loss. Its absence could be a consequence of the reduction of the median clypeal fringe. However, if the clypeal configuration in Baracidris and some Adelomyrmex ( A. biroi and A. hirsutus ) is postulated to be ancestral, that is to say, the median portion of the clypeus represented merely by a narrow fringe, and the configuration in the species of the genus Adelomyrmex is the derived condition, it can be thought that a central seta is an apomorphy for this genus alone, rather than for the Adelomyrmex genus-group.

 

The Solenopsis genus group possesses an apical clypeal seta projected forward (Bolton, 1987). However, this group exhibits other traits (number of antennomeres in antennae and antennal club) that excludes the possibility of the inclusion of Adelomyrmex (and Baracidris ) in the group. The median clypeal seta is also observed sporadically in some Stenammini . Because the nearest tribe to Solenopsidini seems to be Pheidologetonini (Bolton, pers. comm.), which lacks the central clypeal seta, I postulate that the presence of a central seta could be a convergence among Solenopsidini , Adelomyrmex genus group and some Stenammini .

 

How could a central seta have evolved in Adelomyrmex ? In the ancestral situation we can imagine a continuous, flat clypeus with a row of apical setae of similar size (as in Myrmica or Tetramorium , Fig. 1). When the median bulge of the clypeus developed, some of these setae "migrated" to different positions, leaving one of them as central, accompanied at sides by paracarinal setae (Ettershank, 1966). In Solenopsidini the clypeus does not present the degree of modifications as in Adelomyrmex genus group; so the presence of a central seta must have an independent origin in this group. The same may be stated for those few Stenammini that possess a central clypeal seta.

 

Geographical distribution. The range of the Adelomyrmex genus-group includes the Neotropical and Afrotropical Regions, New Guinea, toward the eastern end of the Oriental Region, and the Samoan and Fijian archipelagoes in Oceania. See "Biogeographical Considerations ", below.

 

Key to genera of Adelomyrmex genus-group

 

1 Basal border of mandible with tooth (as in Fig. 54); apical clypeal seta usually present (as in Fig. 9) and hypostomal bridge with median tooth as in (Fig. 29) or petiolar node low, poorly differentiated (Figs. 64, 65); Neotropics, New Guinea, Fiji, Samoa .......... ...................................................................................................... Adelomyrmex Emery

 

- Basal border of mandible unarmed (Fig. 69); apical clypeal seta absent or not noticeable(Fig. 69); hypostomal bridge simple; node of petiole high (Fig. 69); West and Central Africa.................................................................................... Baracidris Bolton

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The genus Adelomyrmex is known from the Neotropical and Australian-Pacific Regions with 12 described species (Bolton, 1995; Fernández & MacKay, 2003), while Baracidris (Bolton , 1981) is a genus with 2 described species from Central and Western Africa. Bolton (1981) suggested that Baracidris is close to Adelomyrmex , based on the shared possession of antennae 12 segmented with 2 segmented club, and established the differences between both taxa. However, this suggested proximity was not reflected in the classification of the subfamily.

 

I propose that both genera form a monophyletic group and I redescribe Adelomyrmex . A revision of all known species of the group is provided, including the description of new species.

 

TAXONOMIC HISTORY

 

The taxonomic history of the group is short. Emery (1897) proposed Adelomyrmex to acommodate a single species, A. biroi from New Guinea. Wheeler (1910) described the genus Apsychomyrmex for a Mesoamerican species, A. myops . Smith (1947) later reviewed this genus. Kempf (1972) placed Apsychomyrmex as a junior synonym of Adelomyrmex . Mann (1921) proposed Arctomyrmex as a subgenus of Adelomyrmex , a name synonymized under Adelomyrmex by Bolton (1994). Bolton (1981) described Baracidris and suggested its close relationship with Adelomyrmex .

 

Forel (1917) placed Adelomyrmex and Apsychomyrmex in the tribe Leptothoracini . Kempf (1972) put Adelomyrmex in the tribe Leptothoracini ; Hölldobler & Wilson (1990) left Adelomyrmex and Baracidris without tribal assignation, and Bolton (1994) placed both genera provisionally in Stenammini .

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Basal border of mandibles with a tooth at or proximal to the midlength of the border.

 

Maxillary palp 1 - segmented (Gotwald, 1969).

 

Median portion of clypeus swept upwards into a strongly raised sharp-edged longitudinal platform which projects sharply forwards into a lobe; anterior clypeal margin sweeping downwards and outwards away from and behind the apex of this lobe.

 

Hairs present on dorsal surfaces of head and body.

 

Postpetiole not short-cylindrical in dorsal view, usually without a truncated ventral process.

 

Petiole usually high and narrow in profile, only rarely low.

 

Metapleural lobes small, separated from the propodeal spines above.

 

Range: Neotropics, New Guinea, Fiji, Samoa.

 

Among the Myrmicinae of the Ethiopian zoogeographical region Baracidris is unique in possessing 12 - segmented antennae with a 2 - segmented club. This character, coupled with the very closely approximated frontal lobes with the median clypeus narrowly inserted between them, the short 5 - dentate mandibles, reduced palp formula of 2, 2 and the shape of the pedicel segments, renders Baracidris quickly recognizable. The key presented below will separate the myrmicine genera of the region which have a conspicuously 2 - segmented antennal club. Crematogaster is included as a few species have such a club although the vast majority of species in this genus have the club 3 - segmented.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Adelomyrmex MAS002

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Specimens with Barcodes: 94
Species With Barcodes: 1
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Statistics of barcoding coverage: Adelomyrmex MAS003

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Specimens with Barcodes: 10
Species With Barcodes: 1
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Statistics of barcoding coverage: Adelomyrmex MAS007

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Specimens with Barcodes: 25
Species With Barcodes: 1
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Statistics of barcoding coverage: Adelomyrmex MAS006

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Public Records: 0
Specimens with Barcodes: 3
Species With Barcodes: 1
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Statistics of barcoding coverage: Adelomyrmex MAS005

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Specimens with Barcodes: 1
Species With Barcodes: 1
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Statistics of barcoding coverage: Adelomyrmex MAS001

Barcode of Life Data Systems (BOLDS) Stats
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Specimens with Barcodes: 3
Species With Barcodes: 1
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Statistics of barcoding coverage: Adelomyrmex SC02

Barcode of Life Data Systems (BOLDS) Stats
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Specimens with Barcodes: 3
Species With Barcodes: 1
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Statistics of barcoding coverage: Adelomyrmex SC01

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 14
Species With Barcodes: 1
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Wikipedia

Adelomyrmex

Adelomyrmex is a genus of ants in the subfamily Myrmicinae.[2] Species of Adelomyrmex are small, litter-inhabiting ants most often collected in Berlese and Winkler samples. Although the genus and its relatives have a pantropical distribution, Central American cloud forests are the only places where they are abundant and diverse.[3]

Habitat and distribution[edit]

The center of Adelomyrmex abundance and diversity is Central America, and a few far-flung species occur in New Guinea, Samoa, Fiji, Tonga, New Caledonia, and Isla del Coco.[3] Several Adelomyrmex species are mountain-top endemics with very restricted ranges, and climate change clearly poses the threat of mountain-top extinction.[3]

The geographic range of the genus in the New World is (1) the mainland from northern Mexico to Amazonian Brazil; (2) the Galápagos, where the mainland species A. myops is probably recently introduced; and (3) Isla del Coco, a small oceanic island north of the Galápagos, with a highly distinctive endemic species. The genus is unknown from the Caribbean islands. The center of abundance and diversity is the Central American highlands south to western Panama. Elsewhere in the range the genus is always very rare with low local diversity.[3]

In Central America, Adelomyrmex occur primarily in mature wet forest habitats, in rotten wood and leaf litter on the forest floor. They are far more abundant in montane cloud forest than in lowland rainforest. In some cloud forest habitats they can occur in nearly 100% of miniWinkler samples (1 m2 samples of sifted litter) and dozens of individuals may occur in samples. In lowland rainforest they are rare, occurring in fewer than 10% of miniWinklers, and usually as one or two individuals per sample. Highland species are typically larger as well. Thus in some cloud forests Adelomyrmex make up a large proportion of the ant biomass (often sharing that role with another dominant cloud forest myrmicine genus, Stenamma). In contrast, in lowland habitats they are very rare and a minute proportion of the biomass. In South America they are always rare, whether in lowlands or cloud forest.[3]

Nests[edit]

Given their abundance in cloud forest Winkler samples, remarkably few nests have been observed. Small nests of A. tristani and A. paratristani are occasionally found in bits of rotten wood on the ground. The dark workers curl and lie motionless on disturbance, blending with the background debris. Only the white brood gives them away. An exception is some montane sites in Guatemala and Chiapas where A. robustus occurs. Adelomyrmex robustus can be a more conspicuous presence, with large colonies in rotten wood at forest edges. Adelomyrmex bispeculum, a species endemic to Monteverde, Costa Rica, is only known from three nest collections. These nests were in small chambers in clay soil, one beneath a stone and two in a vertical trailside bank. It is revealing that this species has not been collected in the hundreds of sifted litter samples taken in the Monteverde area, in which A. tristani is very abundant. It suggests fine-scale microsite segregation of Adelomyrmex species.[4]

Biology[edit]

Head of a Adelomyrmex myops dealate queen

Foragers are almost never seen. Adelomyrmex workers generally have small eyes and presumably forage almost entirely beneath the litter. In baiting transects in cloud forest, Adelomyrmex are occasionally encountered, but not in numbers that reflect their abundance in sifted litter samples. Nothing is known of their feeding habits.[3]

The reproductive biology of Adelomyrmex is mysterious. In Winkler samples, Adelomyrmex workers are routinely accompanied by wingless queens and intercaste individuals. The queens are about the same size as workers but with ocelli, large compound eyes, and the typical enlarged mesosoma of myrmicine queens. The typical sclerites of winged queens and apparent wing scars are present. One queen of A. silvestrii from a Winkler sample has a shred of membranous wing, as though it were irregularly torn or chewed off. Intercaste individuals show variable intermediacy between workers and queens, with variable presence of a single median ocellus, compound eyes of intermediate size, and an enlarged promesonotum.[4] In spite of the relative commonness of these putative reproductives, males and winged queens are rare in Central America. None have appeared in hundreds of Winkler samples, and none have appeared in Malaise samples from the same sites where Adelomyrmex are abundant in the litter. The only known winged reproductives in the genus are the single report of males and alate queens of A. vaderi, a species from Colombia.[4]

Species[edit]

References[edit]

  1. ^ Bolton, B. (2014). "Adelomyrmex". An online catalog of the ants of the world. Retrieved 3 July 2014. 
  2. ^ "Genus: Adelomyrmex". antweb.org. AntWeb. Retrieved 23 September 2013. 
  3. ^ a b c d e f Longino 2012, p. 2
  4. ^ a b c Longino 2012, p. 3
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