Megalomyrmex

Longino, John T., 2010, A taxonomic review of the ant genus Megalomyrmex Forel (Hymenoptera: Formicidae) in Central America, Zootaxa 2720, pp. 35-58 : 37-41

Key to the species of Megalomyrmex

This key covers the region from central Panama to the northern limit of the genus in Mexico. Megalomyrmex reina , known only from queens, is not keyed.

1 Mandibles with 5 distinct teeth, apical tooth largest, proximal tooth next largest, remaining three teeth the smallest and subequal in size ( Fig. 1 A); ML greater than 1 mm ................................................................................................ 2

- Mandibles with a large apical and subapical tooth, and a series of usually 4 or more smaller basal teeth ( Figs 1 B–F); if only 3 basal teeth (some specimens of drifti ), then ML less than 1 mm ................................................................... 4

2 Dorsal surface of mandible striate; occipital carina not visible in face view. Costa Rica to Venezuela........................ ...................................................................................................................................................... M. modestus Emery

- Dorsal surface of mandible largely smooth with large piligerous punctures; occipital carina visible or not............... 3

3 Metanotal groove very deep and broad; propodeum broadly curved, without differentiated dorsal and posterior faces ( Fig. 2 A); ventral margin of postpetiole protruding, evenly convex, without anteroventral spine. Costa Rica to Guianas, Amazonian Brazil.................................................................................................................... M. wallacei Mann

- Metanotal groove less strongly impressed; propodeum with differentiated dorsal and posterior faces, and often with pair of blunt tubercles ( Fig. 2 B); ventral margin of postpetiole flat, sloping anteriorly, anterior margin often terminating in long, needle-like spine. Costa Rica south to Andean regions of Colombia, Ecuador, and northern Peru............ ............................................................................................................................................................. M. foreli Emery

4 Dorsal surface of mandible coarsely striate; color orange brown; body covered with dense, yellow pilosity............. 5

- Dorsal surface of mandible entirely smooth or smooth distally and striate only at base; color and pilosity various... 6

5 Dorsal pilosity thin and flexuous ( Fig. 3 A); scape relatively short (SI 90–93); ventral keel of petiole Y-shaped, anterior carina splitting into two and forming two diverging posterior arms ( Fig. 3 C). Costa Rica and Panama, possibly further south into South America......................................................................................... M. symmetochus Wheeler

- Dorsal pilosity coarse and stiff ( Fig. 3 B); scape relatively long (SI 94–98); ventral keel of petiole interrupted, a single median carina anteriorly, two short subparallel carinae posteriorly ( Fig. 3 D). Panama, possibly further south into South America...................................................................................................................... M. adamsae new species

6 Eyes very small, <6 facets across greatest diameter; color yellow orange................................................................... 7

- Eyes larger,>10 facets across greatest diameter; color usually red brown to black ( silvestrii specimens may occasionally be pale brown) ................................................................................................................................................. 8

7 Foraminal carina (on the posterior face of the propodeum) complete ( Fig. 5 B); subpetiolar process with a transversly sculptured flange. Costa Rica.............................................................................................................. M. miri Brandão

- Foraminal carina incomplete ( Fig. 5 A); subpetiolar process a laterally compressed tooth, not a transverse flange. Costa Rica and Panama............................................................................................................... M. wettereri Brandão

8 Petiolar node in lateral view robust, subtriangular, with anterior face straight, steeper than posterior face ( Fig. 4 A); scape short (SI ~92); mandible subfalcate, 4–7 basal teeth, often with the second tooth from the base larger than the flanking teeth ( Fig. 1 D). Southern Mexico south to central Brazil and Peru, absent in Costa Rica.............................. .................................................................................................................................................. M. incisus M.R. Smith

- Petiolar node thinner, anterior face slightly concave, less steep than posterior face ( Fig. 4 B); scape length various (SL 75–140); mandible more triangular, not falcate, basal teeth of more uniform size, gradually increasing in size apically, or rarely with second from base slightly larger than others ( Figs 1 C, E, F) .................................................. 9

9 Scape not or barely surpassing vertex margin (SI 79–95); HW <0.60 mm; mandible with 3–5 small teeth proximal to larger distal pair ( Fig. 1 C); clypeus usually with pair of longitudinal carinae. Southern Mexico to southern Brazil............................................................................................................................................................. M. drifti Kempf

- Scape distinctly surpassing vertex margin (SI> 95); HW> 0.60 mm; mandible with five or more teeth proximal to distal pair ( Figs 1 E, F) ................................................................................................................................................ 10

10 Mandible with series of 12 or more minute teeth proximal to distal pair ( Fig. 1 E); median portion of clypeus protruding and the anterior margin of clypeus recessed, such that in face view the median portion of the clypeus partially obscures the anterior margin; scape long (SI 115–120). Southern Mexico to northern Argentina................................. .................................................................................................................................................... M. silvestrii Wheeler

- Mandible with series of 7–10 teeth proximal to distal pair ( Fig. 1 F); clypeus not protruding, anteromedian margin visible in face view; scape length variable.................................................................................................................. 11

11 Foraminal carina incomplete, absent dorsally ( Fig. 5 A); anterior clypeal margin more produced and subangular, not evenly rounded ( Fig. 5 C); scape relatively short (SI <103). Costa Rica............................ M. nocarina new species

- Foraminal carina complete ( Fig. 5 B); anterior clypeal margin evenly rounded ( Fig. 5 D); scape relatively long (SI> 105) ............................................................................................................................................................................ 12

12 Scape relatively long (SI> 120); juncture of dorsal and posterior face of propodeum evenly convex ( Fig. 6 A); occipital carina relatively more developed ( Fig. 6 A); for most collections, basal tooth on the masticatory margin of the mandible similar in size to the more distal teeth, such that the juncture of the basal and masticatory margins forms a well-defined angle ( M. mondabora holotype shows contrasting condition found in M. mondaboroides ). Costa Rica............................................................................................................................................... M. mondabora Brandão

- Scape relatively short (SI <114); juncture of dorsal and posterior face of propodeum moderately depressed, flat to slightly concave ( Fig. 6 B); occipital carina relatively less developed ( Fig. 6 B); basal tooth on mandible smaller than more distal teeth, such that the basal and masticatory margin have a more rounded juncture. Costa Rica and Panama, possibly further south into Ecuador, Brazil................................................................ M. mondaboroides new species

Figures

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

FIGURE 2. Mesosomal profile of (A) wallacei and (B) foreli.

FIGURE 3. Dorsal pilosity of (A) symmetochus and (B) adamsae. Ventral petiolar keel of (C) symmetochus and (D) adamsae.

FIGURE 4. Lateral view of petiole of (A) incisus and (B) drifti.

FIGURE 5. Foraminal carina (viewing posterior face of propodeum) of (A) nocarina and (B) mondaboroides. The foraminal carina is a distinct, elevated rim around the foramen in the posterior face of the propodeum, above the insertion of the petiole. It varies in completeness and may be absent dorsally, as in nocarina. Anterior clypeal margin of (C) nocarina and (D) mondaboroides.

FIGURE 6. Contrasting propodeal shape and occipital carina of (A) mondabora and (B) mondaboroides.