Aenictus aratus Forel

Shattuck, S. O., 2008, Review of the ant genus Aenictus (Hymenoptera: Formicidae) in Australia with notes on A. ceylonicus (Mayr)., Zootaxa 1926, pp. 1-19 : 4-7

Aenictus aratus Forel

(Figs 4-6, 7, 8, 25)

Aenictus aratus Forel , 1900: 74.

Aenictus pachycerus impressus Karavaiev , 1927: 7 ( new synonym).

Types. A. aratus : Three worker syntypes ( MCZC, examined) from Mackay, Queensland. A. pachycerus impressus : Lectotype worker from Mackay, Queensland, here designated ( MHNG).

Diagnosis. Head capsule completely punctate; scape relatively short (SI <103); pronotum entirely sculptured with dense micro-reticulations. This species can be separated from the morphologically similar A. nesiotis by the broader head (CI> 87 and HW> 0.70mm compared to CI <88 and HW <0.70mm) and the relatively shorter scapes (SI <103 compared to SI> 107 in A. nesiotis ).

Worker Description. Mandible triangular with numerous small teeth, those along the medial region of the masticatory margin ill defined; anterior clypeal border broadly convex, extending slightly anterior of frontal lobes; parafrontal ridges well developed, extending posteriorly approximately 1/3 length of head capsule; subpetiolar process broadly convex anteriorly, flat posteriorly; head entirely punctate; mesosoma uniformly punctate, generally with weak, ill-defined longitudinal rugae on dorsum of pronotum and lateral surfaces posterior of pronotum; body brown to black, anterior section of head sometimes lighter, distal antennae and legs always lighter.

Measurements. Worker (n = 18) - CI 87-93; HL 0.78-0.88; HW 0.70-0.78; MTL 0.67-0.75; ML 1.17- 1.29; SI 96-103; SL 0.70-0.78.

Material examined. Australia: Queensland: 20km S Sarina Ridge (Lowery,B.B.) ( ANIC); 50km NW Townsville (Greenslade,P.J.M.) ( ANIC); Henrietta Ck., Palmerston NP (Ward,P.S.) ( ANIC); Hinchinbrook Is., Gayundah Ck. (Davies, Thompson & Gallon) ( ANIC); Mackay (Turner) ( ANIC); Northern Territory: Minaelu Creek, Melville Island (Mann,S.) (TERC).

Comments. This species was previously thought to be wide spread and occurring from India eastward into Australia (Wilson, 1964). However, as conceived here this species is restricted to Australia with extraAustralian specimens being referable to A. aitkenii, A. levior and likely additional as-yet unrecognised species. Detailed examination of this material will be required to resolve the true taxonomic status of these non-Australian ants.

Aenictus pachycerus impressus Karavaiev is here synonymised with A. aratus . The nomenclatural history of this name is rather complicated. It was first used by Karavaiev (1926) when describing the variety levior (as Eciton (Aenictus) impressus var. levior ). The next year Karavaiev (1927) noted that A. impressus had actually never appeared in print and that he had used the name based on a specimen identified and labelled with this name that he had received from Forel. He then contacted Forel who provided notes from his 1893 notebook which listed the name " Aenictus bengalensis Mayr rasse impressus nov. subsp. ", followed by a short description complete with comparisons to A. aitkenii and A. bengalensis . The name impressus was not mentioned again until Bolton (1995) included it in his catalogue, listing Karavaiev (1927) as the author and noting that the type locality was unknown but was probably India.

During this study two specimens from the Forel Collection (Geneva) were found which were labelled as " Ae. impressus For . type" from Mackay, Queensland and collected by Turner, with the label being typical of Forel's handwriting. These specimens had been more recently labelled as A. aratus and were stored with other " aratus " specimens, clearly indicating that they were considered to be types of A. aratus . This treatment is supported by the original description of A. aratus (Forel, 1900) where Mackay is listed as the type locality and Turner as the collector (and where comparisons are made to A. aitkenii and A. bengalensis ).

Assembling this information, what seems to have happened is that Forel (around 1893) determined that he had a new taxon which he intended to name impressus and labelled the specimens using this name. However, when preparing the 1900 description he changed the name to A. aratus but neglected to update the specimen labels. He then sent a pin from this series to Karavaiev, who used the name on the specimen ( impressus ) when establishing A. levior (Karavaiev, 1926) not realising that this name was unpublished. Karavaiev (1927) then made matters worse by providing enough information for the name to be considered available by Bolton (1995). To confuse things further Forel's (1893 notes and 1900) comparisons with the Indian species A. aitkenii and A. bengalensis implied that this is an Indian species. In fact, it would appear that both of these names, A. aratus and A. impressus , are based on the same type series from Mackay, Queensland. Using this assumption, a single specimen housed in Geneva is here selected as the lectotype for both names, relegating A. impressus as a junior objective synonym of A. aratus .

The published literature for this species is limited. Wilson (1964) discussed the biology and taxonomy of this and related species (under the single name " A. aratus ") and Disney and Kistner (1991) discuss parasitism by phorid flies.