Correcting our correctors: the search for the true Dacetini
C. Baroni Urbani & M. L. de Andrade

     Baroni Urbani & de Andrade (1994) merged the ant tribes Basicerotini and Dacetini in one, an opinion promptly contrasted by Bolton (1995), who gives no reasons for it, and by Bolton (1998), who characterizes for the first time his tribe ‘Dacetonini’ by means of two synapmorphic characters.

     This is a very important step in Bolton’s classificatory design since separation of the two tribes allows consideration of genus-level characters in one tribe only, even if same trait is present in true or presumed genera of the other, related tribe.

The two tribal synapomorphies of the Dacetini s. str. are:

1. Presence of a basimandibular process (assumed to be absent in all other related genera). Even so, Bolton (1998:72) admits that reputed non-dacetines exhibit the same or a similar morphology, since “basicerotine species with a modified basal tooth are exceptional and certainly best regarded as independent acquisitions”. The validity of this reasoning, however, depends on the fact that the species in question were already considered as non-Dacetini before defining which ones are the true Dacetini.

     Nonetheless, we are willing to believe this explanation, although we are unable to substantiate it in a number of instances.

     A much stronger refutation of the potential phylogenetic value of this character comes from the fact that the basimandibular process believed to be characteristic of the Dacetini is invisible or absent in some widespread, undoubted Dacetini species like Strumigenys argiola (Emery) (Fig. 1), (combination in Strumigenys by Baroni Urbani, 1998). Other examples of undoubted Dacetini without visible basimandibular process will be given in a forthcoming paper already submitted by C. Baroni Urbani & M. L. de Andrade: “The ant tribe Dacetini: limits and constituent genera (Hymenoptera, Formicidae)”.

Fig. 1. Dorsal view of the right mandible of Strumigenys argiola (Emery) without discernible traces of basimandibular process.

2. The second (and last) dacetine synapomorphy is the “labrum with an impression… on the labral shield, distal of the basal hinge but proximal to the labral lobes” (Bolton, 1998: 72). Only one year later, the validity of this character is implicitly negated by Bolton himself (1999: 1681) where one can read that the “labrum mediodorsally with a very broadly and deeply concave depression in its proximal half” is synapomorphic for the genus Epopostruma alone. One more year later (Bolton, 2000: 12) this character is omitted from the diagnosis of Dacetini.

     We are unable to recall the existence of other commonly recognized ant tribes so ill defined as the above Dacetini.

References

Baroni Urbani, C. 1998. Strumigenys baudueri (Emery): espèce nouvelle pour la Suisse (Hymenoptera: Formicidae). Bulletin de la Société entomologique Suisse 71: 163-164.

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. 1995. A new general catalogue of the ants of the world. Harvard University Press, Cambridge, Massachusetts, 504 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. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). Journal of Natural History 33: 1639-1689.

Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute 65: 1028 pp.