Aenictus ceylonicus

Little is known about the biology of .

Identification
A member of the ceylonicus group.

Key to Aenictus species groups

Distribution
Aenictus ceylonicus is probably restricted to the western part of the Oriental region (India and Sri Lanka) (Jaitrong & Yamane, 2013). The Australian records shown on the occurrence map below are subspecies that have been raised to full species.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Papua New Guinea, Philippines. Oriental Region: India, Sri Lanka. Palaearctic Region: China, Japan.

Nomenclature

 *  ceylonicus. Typhlatta ceylonica Mayr, 1866a: 505 (w.) SRI LANKA. Wheeler, G.C. & Wheeler, J. 1984: 265 (l.). Combination in Aenictus: Dalla Torre, 1893: 7. Senior synonym of formosensis, latro: Wilson, 1964a: 452. See also: Shattuck, 2008c: 16.
 * latro. Aenictus ceylonicus var. latro Forel, 1901a: 477 (w.) INDIA. Junior synonym of ceylonicus: Wilson, 1964a: 452.
 * papuanus. Aenictus papuanus Donisthorpe, 1941c: 129 (w.) NEW GUINEA. Junior synonym of ceylonicus: Wilson, 1964a: 452.
 * similis. Aenictus similis Donisthorpe, 1948g: 131 (w.) NEW GUINEA. Junior synonym of ceylonicus: Wilson, 1964a: 452.

Type Material


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 Aenictus ceylonicus (strict sense), Aenictus acerbus, Aenictus orientalis, Aenictus papuanus, Aenictus prolixus and Aenictus 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.

Worker
Wilson (1964) - Syntypes: HW 0.62 mm, HL 0.62 mm, SL 0.50 mm; HW 0.54 mm, HL 0.60 mm, SL 0.44 mm. Antenna 10-segmented. Mandible narrow, bearing 1 large apical and 1 large preapical tooth; the basal portion right-angulate, which can be interpreted as a 3rd "basal" tooth. When mandibles are closed there remains a gap between their posterior borders and center of anterior clypeal border almost as wide as maximum width of mandible. Clypeus emarginate, not armed. Parafrontal ridge rudimentary. Occiput very feebly convex, lacking a collar. Propodeal junction surmounted by low, rounded, transverse ridge, which in side YIGW appears as a "rounded" right angle. Subpetiolar process a long, thin, evenly rounded lobe which projects anteriorly. Pilosity abundant and relatively long; length of longest hairs on pronotum about 0.16 mm.

Head entirely shining. Pronotum shining. Mesothorax and propodeum bearing 15-20 longitudinal rugae, their interspaces weakly microreticulate and feebly shining. Sides of petiole and postpetiole microreticulate and subopaque, their tops shining. Concolorous clear yellow.