Leptanilla palauensis

Distribution based on Regional Taxon Lists
Indo-Australian Region: Palau.

Nomenclature

 *  palauensis. Probolomyrmex palauensis Smith, M.R. 1953c: 128, figs. 1, 2 (m.) PALAU IS. Combination in Leptanilla: Taylor, 1965d: 363. See also: Petersen, 1968: 596.

Taxonomic Notes
Petersen (1968) - This male-based species from the Palau Islands was originally described in the ponerine genus Probolomyrmex by Marion R. Smith (1953, p. 127, figs. 1-2), but was later excluded from that genus and transferred to the Leptanillinae, with a queried assignment to the genus Leptanilla, by Taylor (1965, p. 363). Taylor gives very good reasons for the transfer to Leptanillinae, but I consider that palauensis is not as close to Leptanilla (or to the almost identical genus Phaulomyrma) as he thought. The conditions of the genitalia of palauensis. are so different from Leptanilla that palauensis probably deserves a genus of its own.

Taylor considered the genitalia of L. palauensis, of Leptanilla javana and of Santschi's Leptanilla species to be similar, mainly in the shape of the gonoforceps, but unfortunately he was misled by Smith's inaccurate description of the genitalia in palauensis. Smith surprisingly confused tergum 8 with the gonoforceps, apparently because tergum 8 has a peculiar form, with long posterolateral projections. These were accepted as apices of gonoforceps (gonostyli) by Taylor, following Smith. However, the peculiar terminal sclerite is in fact the tergum of the eighth abdominal segment, and it should be noted that Smith's figure 2 shows a spiracle on this sclerite. At my request Dr. David R. Smith has kindly examined the type of palauensis located in the collections of the U.S. National Museum, Washington, and he confirms my view on the identity of the sclerite in question. After this correction it is clear that the genitalia of palauensis bear no obvious resemblance to those of Leptanilla and Phaulomyrma, apparently being at least partly retractile and presumably without large gonocoxites. Information and sketches provided by Dr. Smith show that the genitalia are apparently very large and unusually retracted, in fact, in such a way that the 6th and following sterna are withdrawn by the genitalia into the abdomen and probably strongly reduced, a most unusual condition. According to Dr. Smith, fig. 2 in the original paper on palauensis is quite wrong in its interpretation of the terminal sterna. On the other hand, however, he has confirmed the figuring of the aedeagus, which is a compressed, blade-like structure with the dorsal edge thicker than the ventral one. It is very long and can be seen from below to extend right into the fifth sternum at about the middle of the abdomen. Dr. Smith has also confirmed the presence of the structures called volsellae in the original description, but these are unfortunately almost hidden under tergum 8. What can be seen are presumably the tips of the volsellar digiti. In Dr. Smith's sketches they are slightly hooked and their bases may be associated with the aedeagus in much the same way as those of Noonilla copiosa (figs. 9, 10).

Unfortunately the U.S. National Museum does not loan holotypes, and until the single specimen of palauensis can be exhaustively studied and its genitalia dissected. I refrain from formally erecting a new genus for this remarkable hymenopteron.

References based on Global Ant Biodiversity Informatics

 * Baroni Urbani C. 1977. Materiali per una revisione della sottofamiglia Leptanillinae Emery (Hymenoptera: Formicidae). Entomologica Basiliensia 2: 427-488.
 * Petersen B. 1968. Some novelties in presumed males of Leptanillinae (Hym., Formicidae). Entomologiske Meddelelser 36: 577-598.
 * Smith M. R. 1953. A new species of Probolomyrmex, and the first description of a Probolomyrmex male (Hymenoptera, Formicidae). Journal of the New York Entomological Society 61: 127-129.
 * Taylor R. W. 1965. A monographic revision of the rare tropicopolitan ant genus Probolomyrmex Mayr (Hymenoptera: Formicidae). Transactions of the Royal Entomological Society of London 117: 345-365.
 * Zolessi, L.C. de and Y.P. de Abenante. 1973. Nidification y mesoetologia de Acromyrmex en el Uruguay III. Acromyrmex (A.) hispidus Santschi 1925 (Hymenoptera: Formicidae) Revista de Biologia del Uruguay 1(2):151-165