Correcting our correctors: the “tribe Phalacromyrmecini”

Cesare Baroni Urbani & Maria L. de Andrade

     The first mention of Phalacromyrmecini as an ant tribe and including the genus Phalacromyrmex alone is due to Wheeler & Wheeler (1976). Since no description accompanied the new name, Phalacromyrmecini Wheeler & Wheeler is a non-available name (nomen nudum).
     Bolton (1984) first detected and described similarities between the genera Phalacromyrmex Kempf, Pilotrochus Brown and his new genus Ishakidris Bolton. Instead of naming a new tribe for these three genera Bolton (l.c.) thought that there is “no advantage to adding yet another formal name to the confusion”.
Dlussky & Fedoseeva (1988) used again the name Phalacromyrmecini making reference to Bolton’s (1984) description and rendered in this way Phalacromyrmecini Dlussky & Fedoseeva a valid tribal name including three monotypic genera: Phalacromyrmex, Pilotrochus, and Ishakidris.
     Baroni Urbani & de Andrade (1994), following Bolton (1984), considered the Phalacromyrmecini as a junior synonym of the Dacetini, a position promptly contrasted by Bolton (1994) who regarded the Phalacromyrmecini as a valid tribe.
     The reasons for this conversion became public four years later, when Bolton (1998) defined the tribe Phalacromyrmecini on the base of three characters. These are:

1. Mandibles with alternating large and small teeth. Bolton (l. c.) recognizes that few species of “Glamyromyrmex” exhibit a similar mandibular dentition, a fact considerably weakening the phylogenetic meaning of this trait. As a matter of fact, the “typical” alternating larger and smaller teeth of the Phalacromyrmecini were already described for other related ants. Previously published examples, among other possible ones, include Strumigenys bunki Brown (well visible also in Bolton, 2000, fig. 113), and Octostruma betschi Perrault (Perrault, 1988: fig. 2). After Bolton’s revival of Phalacromyrmecini, Terayama, Lyn & Wu (1996) described “Smithistruma” kichijo with alternating small and large teeth and we observed the same morphology also in Octostruma balzani (Emery).
Considering that the “tribe Phalacromyrmecini” comprises three monotypic genera only, i.e. just three species, and that at least four closely related but non-phalacromyrmecine species exhibit the same morphology, one may legitimately wonder about the significance of this trait.
2. Presence of a katepisternal oblique groove. While reading and trying to understand the description of this trait we hesitated on its phylogenetic meaning and validity as a tribal character. Suppose discovering a Camponotus or a Pheidole with katepisternal oblique groove, should you put it in a new tribe? Fortunately the Phalacromyrmecini case allows an unmistakable solution without answering this question. The type genus of the tribe, Phalacromyrmex, and the second genus of the tribe, Pilotrochus, have no trace of katepisternal groove. The fact was well known to Bolton since in his description of Ishakidris (1984: 378) he uses this same feature to differentiate Phalacromyrmex (groove absent) from Ishakidris (groove present). A few pages later in the same paper Bolton (1984: 381) adds that the “mesopleural organ… in Pilotrochus…is…not subtended by the open groove seen in Ishakidris”. The katepisternal groove, hence, in this context was created for the sole purpose of separating the Phalacromyrmecini as a valid tribe.

Phalacromyrmex fugax Kempf, holotype worker from the Museum of Zoology, San Paulo. Courtesy of Dr. C. R. F. Brandão. Profile of the mesosoma showing no traces of the katepisternal groove, the reputed most distinctive character of the “tribe Phalacromyrmecini”.

3. Scape clavate. At first glance, this character might need a slightly less ludicrous approach than the previous two. It will be exhaustively dealt with in a forthcoming paper already submitted by C. Baroni Urbani & M. L. de Andrade: “The ant tribe Dacetini: limits and constituent genera (Hymenoptera, Formicidae)”.

     Exception made for the lifelong work of George C. and Jeannette Wheeler, the ant taxonomy is based essentially on adult (imago) morphology. This means that the resulting classification should be drawn essentially on imaginal, and not on imaginary characters.

References

Baroni Urbani, C. & Andrade (de), M. L. 1994. First description of fossil Dacetini ants with a critical analysis of the current classification of the tribe. Stuttgarter Beiträge zur Naturkunde, B 198: 1-65.
Bolton, B. 1984. Diagnosis and relationships of the myrmicine ant genus Ishakidris gen. n. (Hymenoptera: Formicidae). Systematic Entomology 9: 373-382.
Bolton, B. 1994. Identification guide to the ant genera of the world. Harvard University Press, Cambridge, Massachusetts, 222 pp.
Bolton, B. 1998. Monophyly of the dacetonine tribe-group and its component tribes (Hymenoptera: Formicidae). Bulletin of the Natural History Museum, London (Entomology) 67: 65-78.
Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute 65: 1028 pp.
Dlussky, G. M. & Fedoseeva, E. B. 1988. Origin and early evolution of the ants. In Ponomarenko, A. G. (Ed.): Cretaceous biocenotic crisis and insect evolution. Pp. 70-144; Moscow (Nauka). Russian.
Perrault, G. H. 1988. Octostruma betschi, n. sp. de Guyane Française [Hymenoptera, Formicidae]. Revue Française d’Entomologie 10: 303-307.
Terayama, M., Lin, C.-C. & Wu, W.-J. 1996. The Taiwanese species of the ant genus Smithistruma. Japanese Journal of Entomology 64: 327-339.
Wheeler, G. C. & Wheeler, J. 1976. Ant larvae: review and synthesis. Memoirs of the Entomological Society of Washington 7: 1-180.