Aenictus ceylonicus

Distribution
This taxon was described from Sri Lanka.

Nomenclature

 * Typhlatta ceylonica: Worker syntypes from Sri Lanka.
 * Aenictus ceylonicus var. latro: Three worker syntypes from Poona, India.
 * Aenictus ceylonicus var. formosensis: Worker syntypes from Taiwan.

Shattuck (2008) offers the following taxonomic notes on this species:

As previously conceived (Wilson, 1964: 452) this species extended from India and Sri Lanka eastward to Taiwan and south to Australia and contained eight junior synonyms (formosensis Forel, latro Forel, orientalis Karavaiev, papuanus Donisthorpe, similis Donisthorpe, and turneri Forel (with its junior synonyms deuqueti Crawley and exiguus Clark)). When discussing the specimens placed in ceylonicus Wilson (1964) recognised at least some of the variation noted in this study (for example, see Wilson’s figs. 37–44), but interpreted this variation as intraspecific. For example he mentioned that the subpetiolar process varies considerably in its development, but did not appreciate that this variation occurs in discrete states and shows a strong geographic pattern suggesting that a series of species are involved. A careful re-examination of these characters, combined with considerably more material, has resulted in significantly different conclusions being drawn compared to Wilson (1964).

An examination of currently available material has found that the old “ceylonicus” contains a large number of species, including A. ceylonicus (strict sense), A. acerbus, A. orientalis, A. papuanus, A. prolixus and A. turneri. To determine the identity of A. ceylonicus itself will require considerable work and is beyond the scope of the present study. However, there are a wealth of morphological characters which allow the development of robust species hypotheses as has been demonstrated above for the Australian fauna. Having said that, morphological differences among species are often subtle and require considerable attention to detail to decipher. The following notes are provided as a starting point for a full revision of these ants.

Most of the Indian specimens share the configuration of the subpetiolar process, which forms a rounded anterior lobe followed by a posterior flat to concave extension ending at the junction with the postpetiole. Others have an elongate rectangular subpetiolar process, including the types of A. latro. Specimens with both of these morphologies can be found throughout Asia including in Taiwan, the Philippines, Vietnam and Indonesia. But while material from Vietnam has a rectangular subpetiolar process it has the dorsal surface of the mesosoma smooth and lacking any indication of the metanotal groove (most other species have at least a weak angle at the metanotal groove). Thus while the shape of the subpetiolar process is important it must be used in conjunction with other characters when determining species boundaries.

While the work undertaken here is preliminary, it clearly shows that the situation surrounding this species, and close relatives, is much more complex than that recognised by earlier workers. As a first step in clarifying this situation the names A. orientalis and A. turneri are treated as valid species, A. papuanus and A. similis are transferred to synonymy with A. orientalis while A. formosensis and A. latro are retained as junior synonyms of A. ceylonicus. However this should be treated as preliminary until all relevant material can be studied in detail.

Additional References

 * Shattuck, S.O. (2008) Review of the ant genus Aenictus (Hymenoptera: Formicidae) in Australia with notes on A. ceylonicus (Mayr). Zootaxa 1926, 1–19.