Aenictus minutulus

Mark K. L. Wong & Benoit Guénard, 2016, Aenictus seletarius, a New Species of Hypogaeic Army Ant from Singapore, with an Updated Key to the Aenictus minutulus Species Group (Hymenoptera: Formicidae: Dorylinae) from Southeast Asia, Annales Zoologici 66 (1), pp. 35-42 : 36-37

Aenictus minutulus species group

Diagnosis. The A. minutulus species group was established by Jaitrong and Hashimoto (2012) from their redefinition and renaming of the Aenictus piercei species group ( Jaitrong and Yamane 2011). From the A. piercei species group, Jaitrong and Hashimoto removed two species ( Aenictus piercei Wheeler et Chapman, 1930 ; Aenictus lifuiae Terayama, 1984 ) and added two new species and one undescribed morphospecies (see synoptic species list of A. minutulus species group below). Jaitrong and Hashimoto (2012) define the A. minutulus species group as follows: “Head in full-face 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 the propodeum; metapleural groove present or absent (mesonotum and propodeum fused); propodeal junction angular. 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.”

Synoptic species list of A. minutulus species group from Southeast Asia

Aenictus changmaianus Terayama et Kubota, 1993 ( Vietnam, Thailand, Cambodia);

Aenictus minimus Jaitrong et Hashimoto, 2012 (North Vietnam);

Aenictus minutulus Terayama et Yamane, 1989 ( Thailand, Sumatra, Java);

Aenictus peguensis Emery, 1895 ( Vietnam, Myanmar);

Aenictus seletarius sp. nov. ( Singapore);

Aenictus sp. 56 of WJT Jaitrong et Hashimoto, 2012 (Borneo, Java);

Aenictus subterraneus Jaitrong et Hashimoto, 2012 (Borneo) .

Updated key to A. minutulus species group from Southeast Asia

The key to A. minutulus group species from South- east Asia ( Jaitrong and Hashimoto 2012) is updated below with the inclusion of A. seletarius in key couplet 5 and transfer of the species A. changmaianus and A. minutulus to an additional key couplet.

1. Promesonotum in profile with clearly convex dorsal outline; propodeum dorsally distinctly lower than promesonotum.............................. 2

–. Mesosoma dorsally almost flat or feebly convex... 4

2. Declivity of propodeum shallowly concave, encircled with a distinct rim (Borneo and Java)...................... A. sp. 56 of WJT Jaitrong et Hashimoto

–. Declivity of propodeum with lateral carinae, but not demarcated basally by a transverse carina...... 3

3. In full-face view posterior margin of head convex; propodeal junction angulated, right-angled; larger species (TL 2.95–3.15 mm; HW 0.52–0.58 mm) ( Vietnam and Myanmar)......... A. peguensis Emery

–. In full-face view posterior margin of head almost straight or feebly concave; propodeal junction roundly angulated; smaller species (TL 2.10–2.15 mm; HW 0.48–0.50 mm) (Borneo).......................... A. subterraneus Jaitrong et Hashimoto

4. Basal margin of mandible with 1–2 small denticles next to large basal tooth and followed by a larger denticle (North Vietnam).................................... A. minimus Jaitrong et Hashimoto

–. Basal margin of mandible with 3–5 denticles that gradually reduce in size toward base of mandible....................................... 5

5. Head square-shaped and almost as wide as long (CI 91–96); antennal scape relatively short (SI 61–64); polymorphic worker caste with largest individuals exceeding 3.10 mm in TL ( Singapore)........................................ A. seletarrius sp. n.

–. Head longer than wide (CI <90); antennal scape relatively long (SI 67–72); relatively smaller species (TL <2.60 mm)............................. 6

6. Metapleural gland bulla relatively large; distance between propodeal spiracle and metapleural gland bulla shorter than or almost as long as spiracular diameter ( Thailand, Vietnam and Cambodia)............... A. changmaianus Terayama et Kubota

–. Metapleural gland bulla relatively small; distance between propodeal spiracle and metapleural gland bulla clearly longer than spiracular diameter ( Thailand, Java and Sumatra).................................... A. minutulus Terayama et Yamane