Aenictus species groups

Jaitrong and Hashimoto (2011. Synopsis of Aenictus species groups and revision of the A. currax and A. laeviceps groups in the eastern Oriental, Indo-Australian, and Australasian regions (Hymenoptera: Formicidae: Aenictinae). Zootaxa, 3128, 1–46. 2012. Revision of the Aenictus minutulus species group (Hymenoptera Formicidae Aenictinae) from Southeast Asia. Zootaxa 3426, 29-44.

Aenictus minutulus group

 * Aenictus changmaianus
 * Aenictus minimus
 * Aenictus minutulus
 * Aenictus peguensis
 * Aenictus subterraneus

(Aenictus piercei group in Jaitrong et Yamane, 2011: 9.) Diagnosis. In an earlier paper (Jaitrong & Yamane 2011) this species group was defined as follows: head in fullface view with occipital corner convex, and posterior margin almost straight to shallowly and broadly concave; occipital margin lacking collar; antenna 10-segmented; antennal scape short reaching only midlength of head; anterior clypeal margin roundly convex, lacking denticles; mandible subtriangular; its masticatory margin with a large apical tooth, medium-sized subapical and basal teeth, and 2-6 denticles between them; basal margin of mandible with conspicuous denticles; frontal carina short; parafrontal ridge absent; with mesosoma in profile promesonotum convex dorsally and sloping gradually to propodeum; metapleural groove present or absent (mesonotum and propodeum fused); propodeal junction angulated; subpetiolar process well developed, triangular or subrectangular. Head and first gastral segment entirely smooth and shiny. Body yellowish brown to reddish brown; typhlatta spot absent.

Size variation occurs among individuals from single colonies.

'''Distribution. '''Southernmost part of Japan, Taiwan, Myanmar, Thailand, Sumatra, and Philippines.

Remarks. This is a group of rather small species, measuring 1.80-3.20 mm in total body length. It is most similar to the Aenictus javanus group in terms of body size and coloration, but in the former the anterior clypeal margin lacks denticles, while it has several denticles in the latter.

The Aenictus piercei group was established by Jaitrong and Yamane (2011) to include five named species occurring in Southeast Asia: Aenictus changmaianus, Aenictus lifuiae, Aenictus minutulus, Aenictus peguensis and Aenictus  piercei. However, after carefully examining the type material and an associated specimen of A. piercei we concluded that this species should be removed from this group and that it is a member of the A. javanus group (A. piercei has denticles on the anterior margin of clypeus). The A. piercei group is renamed here as the A. minutulus group.

After a careful examination of the smaller specimens of A. lifuiae collected from Iriomote-jima and Okinawajima, southern Japan, we found that the mandible is almost linear, the anterior clypeal margin is straight or weakly concave, and that a gap occurs between the mandibles and anterior clypeal margin. These characteristics are used to separate the A. ceylonicus group from the other groups of the genus Aenictus, and also these specimens possess other conditions shared with the A. ceylonicus group. We transfer A. lifuiae to the A. ceylonicus group.