Megalomyrmex mondaboroides Longino

Longino, John T., 2010, A taxonomic review of the ant genus Megalomyrmex Forel (Hymenoptera: Formicidae) in Central America, Zootaxa 2720, pp. 35-58 : 49-51

Megalomyrmex mondaboroides Longino , new species

( Figs 1 E, 5B, 5D, 6B, 9A–H)

Megalomyrmex mondabora Brandão (part): Adams & Longino, 2007:136 -143.

Type material. Holotype worker. PANAMA, Panama: El Llano, 9.27956°N 78.96150°W, 300 m, 30 Mar 2001 (H. Fernandez-Marin#HF 010330 –50) [ MCZ, unique specimen identifier JTLC 000015325]. Paratypes: Same data as holotype, 1 queen, 1 male [ MCZ, CASENT 0613246, CASENT 0613247], 1 worker [ MZSP, CASENT 0613228], 1 queen, 1 male, 1 worker [ CAS, CASENT 0613229], 2 workers [ USNM, USNMENT 693033, USNMENT 693032], 1 worker [ LACM, JTLC 000015326]; discrepancy in paratype CASENT 0613230; same data as holotype except (C. Currie#CC 010324 –50), 2 workers [ USNM, CASENT 0613226, CASENT 0613227].

Geographic range. Panama, Costa Rica.

Diagnosis. Worker differing from M. mondabora as follows: (1) scape shorter, SI <114; (2) frontal carinae relatively smaller and less elevated; (3) occipital carina thinner, less pronounced; (4) propodeum less convex, medial portion above petiolar insertion usually flat to slightly concave; (5) color black to lighter red brown (always dark red brown to black in mondabora ). Queen differing as follows: (1) scape shorter, SI <105 vs.> 113; (2) frontal carinae relatively smaller and less elevated; (3) occipital carina thinner, less pronounced. Male differing as follows: (1) size smaller, HW <0.8 vs.> 0.8; (2) frontal carinae relatively smaller and less elevated; (3) occipital carina thinner, less pronounced; (4) antennae completely white (segments 7 and above more strongly infuscated in mondabora ).

Description. Worker. Measurements (holotype): HW 0.718, HL 0.783, SL 0.851, EL 0.231, ML 1.180, CI 92, SI 109.

Measurements (n=6): HW 0.605–0.721, HL 0.642–0.788, SL 0.682–0.866, EL 0.188–0.261, ML 0.893–1.180, CI 91–94, SI 106–110.

Palp formula 4,3; mandible with large apical and subapical teeth, 8–10 smaller basal teeth; most basal tooth smaller than adjacent distal tooth, so that juncture of basal and masticatory margin of mandible is rounded; dorsal surface of mandible smooth and shiny; occipital carina narrow, not visible in full-face view, anterior ends extending a short distance onto ventral surface of head, not much beyond level of foramen; face, clypeus, and ventral surface of head smooth and shiny, with a few irregular rugulae on clypeus; mesosoma largely smooth and shiny, with variable development of coarse longitudinal carinae on posterior katepisternum and metanotal groove; foraminal carina an entire semicircle delimiting propodeal foramen, some specimens with a second concentric carina above foraminal carina; petiole and postpetiole smooth and shining, posterior peduncles of both with a few concentric carinulae dorsally; ventral margin of petiole flat, with a very small anterior tooth and almost no development of a ventral keel; ventral margin of postpetiole flat; gaster smooth and shining; all dorsal body surfaces and appendages with abundant flexuous setae; color red brown, with appendages and mandibles lighter brown to a variable degree.

Queen. Measurements (n=1): HW 0.813, HL 0.847, SL 0.874, EL 0.317, ML 1.286, CI 96, SI 103.

Palp formula 4,3 or 3,2; general shape, sculpture, and pilosity characters, including mandibular dentition and sculpture, similar to worker; parapsidal lines present, extending from posterior border of mesoscutum to midlength; wing venation as in Fig. 9 H.

Male. Measurements (n=2): HW 0.723–0.749, HL 0.639–0.658, SL 0.291–0.334, EL 0.350–0.355, ML 1.157–1.167, CI 113–114, SI 46–51.

Palp formula 4,3 or 3,3; mandible with large apical tooth, more than twice length of subapical tooth, subapical tooth followed by 5 small basal teeth of somewhat irregular size and spacing; antenna with kinks in basal segments, strongly flexed between 3rd and 4th segment, 4th segment bent at 3/4ths length, 5th segment bent at midlength, 6th segment bent near base, remaining segments straight; occipital carina very thin, not developed as a distinct flange; fused notaulae present anteromedially, parapsidal lines distinct; wing venation similar to queen but more feeble; ventral margin of petiole a more delicate version of condition in worker and queen; abundant flexuous suberect setae on dorsal head, mesosoma, and metasoma; color dark red brown to black with wings, legs (including coxae), entire antenna (including apex), and mandible contrasting ivory, nearly white.

Biology. Megalomyrmex mondaboroides occurs in lowland wet forest habitats in Panama and Costa Rica. Colonies have been collected in the nests of small attines, primarily Cyphomyrmex costatus Mann and Apterostigma goniodes Lattke. In Costa Rica a worker was collected in a Winkler sample of sifted leaf litter.

Etymology. The name of this species refers to its similarity to M. mondabora .

Comments. Megalomyrmex mondaboroides and M. mondabora are very similar species, and they were treated as a single variable species in Adams and Longino (2007). There is now evidence that the two forms are sympatric in Costa Rica, and molecular evidence suggests that the two are probably sister taxa (Adams, pers. comm.). There are also hints that both may further resolve into multiple cryptic species. Collections from Panama include two nests found with Cyphomyrmex costatus and two nests found with Apterostigma gonioides . The workers with C. costatus are relatively small, with HL <0.70 mm, while the workers from A. gonioides are larger, with HL> 0.78 mm. An isolated worker from Costa Rica is also larger, with HL about 0.78. In the case of M. mondabora , there are contrasting forms of mandibular dentition (described in the key to species). Numerous collections of a form with a large basal denticle on the mandible have been made from nests of C. cornutus , and this form was the subject of the behavioral study of Adams and Longino (2007). In contrast, the holotype of M. mondabora has the small basal denticle and rounded junction of M. mondaboroides . The holotype also differs in host association; it was accompanied by fieldnotes indicating it was associated with an Apterostigma Mayr nest. The types were collected by the renowned myrmecologist W. L. Brown, Jr., and it is inconceivable that he could have misidentified the genus (i.e., misidentifying C. cornutus ). Thus in both M. mondaboroides and M. mondabora there is the potential for further division, perhaps paralleling specialization on various attine hosts. Further host-associated collections of these elusive ants are needed.

In South America, scattered collections of M. mondabora -like ants are known from Ecuador, Peru, and Amazonian Brazil. Many were collected with attine hosts. Morphologically they blur the distinctions that separate the sympatric M. mondaboroides and M. mondabora in Costa Rica. One can anticipate a considerably more complex story when the group is better collected throughout the range.

Additional material examined. COSTA RICA: Heredia: La Selva Biological Station, 10°24'59"N, 084°01'12"W, 50 m, mature wet forest, 14 Jun 2004 (M Molina, D Alvarez, G Hurtado ); PANAMA: Pipeline Road km 2.0, 09°09'36"N, 079°44'42"W (C. Currie); Barro Colorado Island, Fausto to Wheeler trail, 09°09'53"N, 079°50'12"W, 23 Dec 2004 (R. Adams); Gamboa, Pipeline Rd, 2.5 km past Rio Frijoles, 72m, 6–8 Jun 2002 (C. J. Marshall).

South American material in the mondabora complex: BRAZIL: Rondonia: Vilhena, 12°43'S, 060°07'W, Nov 1973 (M. Alvarenga); Sao Paulo: Picinguaba, P. E. Serra do Mar, 23°20'10"S, 044°50'15"W, 100 m, 30 Mar–4 Apr 2001 (C. R. F. Brandão); ECUADOR: Napo: Tiputini, Matapalo Trail, 00°38'18"S, 076°08'58"W, 14 Jun 2003 (C. Currie); Pichincha: Unión del Toachi Station, 4 km SE of station, 00°19'16"S, 078°56'22"W, 875 m, 15 Mar 2006 (R. Adams); PERU: Madre de Dios: Manú, Huacaria, 12°54'10"S, 071°25'25"W, 600 m, 28 May 2004 (R. Adams).

Figures

FIGURE 1. Variation in mandibular dentition among (A) foreli, (B) symmetochus, (C) drifti, (D) incisus, (E) mondaboroides, and (F) silvestrii.

FIGURE 9. Megalomyrmex mondaboroides. A. Holotype worker, face view. B. Same, lateral view. C. Paratype queen, face view. D. Same, lateral view. E. Paratype male, face view. F. Same, lateral view. G. Male antenna. H. Queen fore and hindwing. Scale bars on face views = 0.5 mm, on lateral views and wings = 1.0 mm.