Megalomyrmex

Longino (2010) - Although widespread in the Neotropics, from southern Mexico to northern Argentina, Megalomyrmex species are never abundant. They occur in low to middle elevation wet to dry forest habitats. Some species are free-living with large diffuse nests in the soil (e.g. Megalomyrmex modestus) or small nests in dead wood (e.g. Megalomyrmex drifti) (Brandão 1990, 2003). Others are specialized social parasites or predators of Attini (e.g. Megalomyrmex mondabora, Megalomyrmex symmetochus, Megalomyrmex wettereri; Wheeler 1925, Weber 1941, Kempf & Brown 1968, Adams et al. 2000, Adams & Longino 2007). Some species have unusual alkaloids (Jones et al. 1991a; Jones et al.1991b; Jones et al. 1999).

Identification
Boudinot et al. (2013) - Males of Megalomyrmex are morphologically heterogeneous; some species resemble “generalized myrmicines” whereas others resemble the strange attenuated males of Neotropical Aphaenogaster. The generalized males may be confused most easily with those of New World native Monomorium, but the reduced petiolar and postpetiolar nodes of Megalomyrmex males, relative to workers, is sufficient to separate the two genera. However, separation of Megalomyrmex males from those of Aphaenogaster deserves special mention, due to the remarkable convergence in body form (even including a kinked and distally swollen metabasitarsus in one case). Males of Megalomyrmex may be separated from those of Aphaenogaster by the following characters: (1) absence of an anterior mesonotal bulge (present in A. honduriana); (2) region of head capsule posterior to ocelli never produced into an elongated and flared collar (present in the A. phalangium complex); (3) absence of an anterobasal metacoxal bulge; (4) presence of the foraminal carina (if developed); (5) presence of the basipetiolar carina.

Identification keys
Key to Central American Megalomyrmex:
 * workers
 * males

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



Biology
Boudinot et al. (2013) - The Neotropical ant genus Megalomyrmex is diverse in form and behavior. Several species tend sternorrhynchans or are predacious (Brandão 1990); others are associates of fungus-growing Attini, having lestobiotic (thief ant), agro-predatory (garden usurper), or xenobiotic (cohabitating guest ant) relationships with their hosts (Adams 2008; Adams, Shah et al. 2012).

Nomenclature

 *  MEGALOMYRMEX [Myrmicinae: Solenopsidini]
 * Megalomyrmex Forel, 1885a: 371. Type-species: Megalomyrmex leoninus, by monotypy.
 * [Type-species not Formica bituberculata, unjustified subsequent designation by Wheeler, W.M. 1911f: 167.]
 * Megalomyrmex senior synonym of Cepobroticus, Wheelerimyrmex: Ettershank, 1966: 101; Brandão, 1990: 415.
 * CEPOBROTICUS [junior synonym of Megalomyrmex]
 * Cepobroticus Wheeler, W.M. 1925d: 168 [as subgenus of Megalomyrmex]. Type-species: Megalomyrmex (Cepobroticus) symmetochus, by monotypy.
 * Cepobroticus junior synonym of Megalomyrmex: Ettershank, 1966: 101; Brandão, 1990: 415.
 * WHEELERIMYRMEX [junior synonym of Megalomyrmex]
 * Wheelerimyrmex Mann, 1922: 29 [as subgenus of Megalomyrmex]. Type-species: Megalomyrmex silvestrii, by original designation.
 * Wheelerimyrmex junior synonym of Megalomyrmex: Ettershank, 1966: 101; Brandão, 1990: 415.

Male
Boudinot et al. (2013) - The diagnosis provided below is derived from examination of the males of the following taxa: M. adamsae, M. brandaoi, M. foreli, M. incisus, M. megadrifti, M. miri, M. milenae, M. modestus, M. mondabora, M. mondaboroides, M. silvestrii, M. symmetochus, M. wallacei, M. wettereri, and M. male 01. Among the Central American Myrmicinae, characters which are unique for Megalomyrmex are indicated in italics.

1. Antenna with 11, or more often 13 antennomeres.

2. Funiculus of antenna as long as, or more often longer than mesosoma.

3. Antennomeres often kinked (distinctly bent or curved).

4. Pedicel cylindrical or subcylindrical, never swollen.

5. Palpal formula 4,3; 3,3; or 3,2.

6. Mandibles worker-like, with distinct basal and masticatory margins and with three to numerous teeth.

7. Head proportional for body size (i.e. head length about one half mesosoma length, HL/ML = 0.47–0.62).

8. Occipital carina and vertex never markedly elongated and flared as a collar.

9. Notauli absent or weakly indicated by short diagonal sulcus with transverse carinae.

10. Metacoxa without an anterobasal bulge.

11. Metasternum with or without a spine-like process.

12. Tibial spur formula 1s–b,1s–b.

13. Ventral margin of tarsal claws smooth, without teeth.

14. Foraminal carina usually present and well-developed, may be absent.

15. Propodeal foramen with a strong foraminal carina, several arcing carinae of equal strength, or no distinct carinae.

16. Pterostigma present, well-developed.

17. Forewing: submarginal cell 1 closed.

18. Forewing: marginal cell 1+2 open (i.e. apical abscissae of R and Rs not fusing at apex of wing).

19. Hindwing: claval region narrow.

20. Petiole and postpetiole nodiform; nodes reduced in height relative to workers and queens.

21. Basalmost area of petiolar dorsum delimited posteriorly by a transversely arcing carina or two lateromedian, sinuate carinae (i.e. basipetiolar carina present).

22. Postpetiole with narrow posterior attachment (i.e. helcium of first gastric tergum narrow).

23. Gastral shoulder present (i.e. first gastric sternum with a transverse angle laterad the helcium).

24. Pygostyles present.

25. Telomere tall in the sagittal plane; not dorsoventrally flatted. Body predominantly shining: pronotum, mesoscutum, mesopleuron and lateral face of propodeum never areolate, foveolate, foveate, or scabrous; these surfaces without lamellae, carinae, denticles, or spines.

Notes/Comments 1. Specimens may (very infrequently) differ in antennomere count from left to right antenna due to variable suturation.

3. One of various antennomeres of the funiculus is always kinked in the silvestrii-group, excluding M. wettereri. Both M. wallacei and M. foreli have the third antennomere apically flattened and kinked. The fourth antennomere of M. mondabora, M. mondaboroides, and M. male 01 is kinked. The function, if any, of the kinked antennomeres of male Megalomyrmex and other genera (e.g.Basiceros and Aphaenogaster) is unknown.

11. This is character six in Bolton’s (2003) diagnosis of the solenopsidine tribe group, which he classifies as not having a metasternal process, with the exceptions of M. latreillei (=M. foreli) and Vollenhovia pertinax. We observed presence of a metasternal process, in addition to M. foreli, in the male and both castes of female of M. leoninus and M. modestus.

12. The tibial spur formula follows Bolton (2003), in this case indicating that the meso- and metatibia have one simple to barbulate spur each.

14. The foraminal carina has various states of development and is effectively absent in M. drifti and M. foreli. We predict that the male of M. nocarina will not have a foraminal carina.

21. The basipetiolar carina is present in all sexes and castes of Megalomyrmex; it is weakly developed in the male of M. modestus. A similar carina is present on the males of several ponerine lineages, but this must be considered homoplasious.

23. This is the twelfth character in Bolton’s (2003) diagnosis of the Solenopsidini.

26. Prior to the discovery of M. longinoi, no Megalomyrmex species were known to have costate sculpture. If the male of M. longinoi has similar sculpture to the worker, then this would be an exception to this character.