Aenictus rotundatus Mayr, 1901

Gómez, Kiko, 2022, A revision of the Afrotropical species of the Dorylinae ant genus Aenictus (Hymenoptera: Formicidae) based on the worker caste, Belgian Journal of Entomology 124, pp. 1-86 : 73-75

Aenictus rotundatus Mayr, 1901

( Figs 56 A–D , 57 A–D , 58)

Aenictus rotundatus MAYR, 1901: 1 (w.)

Syntype, SOUTH AFRICA Cape Town (1W) NHMB [Examined] ; Syntype, same data (1w) NHMB [Examined] ; Syntype, SOUTH AFRICA: Capeland 1895 (2w) MHNG: Coll. Forel [Examined] ; Syntype, SOUTH AFRICA: Eastern Cape, Port Elizabeth (1w) [CASENT0919641] NMHW: Coll. Mayr [Examined].

Aenictus rotundatus var. merwei SANTSCHI, 1932: 382 (w.)

Syntype, SOUTH AFRICA: Montagu C. P. (Western Cape) 1.i.1920 (Merve) NHMB [ CASENT0911439 ] [Material seen on web] ; Syntypes, same data (4w) [ NHMUK012849252 ] BMNH [Examined] . Syn. nov.

Aenictus furibundus Arnold, 1959: 335 , fig. 20 (w.)

Syntypes, ZIMBABWE: Cashel, S. Rhodesia . 16.xi.1916 (Arnold, G.) (6w) [ BMNH(E)1015732 , CASENT0902688 ] BMNH [Examined] . Syn. nov.

DIAGNOSIS. The species as defined here is highly variable in subpetiolar process, colour and sculpture, and maybe candidate for being a cryptic species complex. Series from Kenya and Tanzania are lighter, smoother and most of the individuals do not present lamellae at the subpetiolar process, measurements and indexes fall nonetheless into the typical A. rotundatus series and clustering analysis fails to differentiate both series.

Types of A. furibundus are identical to types of A. rotundatus . Curiously enough, ARNOLD (1959) uses A. eugenii for comparison, and not A. rotundatus . These two series are strongly reticulated and dark brown, except for some individuals with smooth dorsopropodeum, petiole and postpetiole. Types of the A. rotundatus var. merwei form are yellowish and much smoother, as stated in its description by SANTSCHI (1932). Nonetheless, as sculpture and subpetiolar lamella have a high degree of variation even in the same nest series, I’d rather consider them as a unique species until genetic data are available.

Details for separation of the rest of species in the complex under A. guineensis, its sibling species.

DESCRIPTION ( Figs 56 A–D , 57 A–D ). WORKER HL: 0.60 [0.45-0.77]; HW: 0.51 [0.37-0.71]; SL: 0.39 [0.26-0.51]; WL: 0.92 [0.69-1.19]; PL: 0.21 [0.15-0.26]; PH: 0.17 [0.12-0.22]; PPL: 0.17 [0.12-0.22]; PPH: 0.16 [0.10-0.25]; CS: 0.56 [0.41-0.74]; CI: 85 [80-92]; SIL: 65 [59-70]; SIW: 76 [69-81]; WL/HW: 178 [164-191]; PI: 121 [109-133]; PPI: 110 [87-128]; CSR: 179; (n=44).

With the characteristics of the rotundatus species complex and: Scapes relatively long, almost reaching three quarters of the head (SL/HL~70).

Funicular segment 2 slightly longer than wide, the rest subquadrate, the apical about twice longer than wide. Head rectangular, longer than wide (CI~90), convex laterally and widest at the middle. Occipital line straight. Ventrolateral margin present, continuing behind the head to one third of its length. Mandibles triangular with a long, sharp apical tooth followed by 5–6 denticles.

Clypeus a row of 10–14 conical teeth, clearly visible and longer than wide, decreasing to the sides, sometimes eroded. Frontal ridges present, not projecting frontally and fused between the antennal sockets.

Pronotum convex, mesopropodeal suture weak, concave and meeting the propodeum at an angle, this with a very reduced but discernible anterior slope and elevated. Transverse mesopleural groove not present. Mesometapleural suture present but very weak; propodeal ridge present but incomplete as a weak line even in the most sculptured specimens, incomplete and weak especially in minor workers, where it can be absent, never as a ridge; propodeal declivity concave below that line.

Petiole sessile with anterolateral and anterodorsal ridges present, dorsolateral ridge present in the most sculptured workers as a thin line to the propodeal spiracle. Petiole with an anterior slope shaped as a quarter of ellipse, dorsal slope flat and almost vertical posteriorly.

Postpetiole subrectangular with rounded angles and vertical anterior and posteriorly, without carinae or ridges of any kind. Subpetiolar process developed with a bulky paralepidepical to ellipsoidal process, followed by a lamellae variable in size from almost non-existent to about the size of the bulky process very short anteriorly and longer posteriorly, convex at the bottom (shark-fin shaped), usually longer posteriorly than anteriorly.

Variable. Types of A. furibundus and A. rotundatus are as follows: head, pronotum and gaster smooth and shining; mandibles finely horizontally rugulose, scapes and funiculus punctuated, shagreened; mesonotum, propodeum, petiole and postpetiole strongly reticulated, matt.

Overall colour dark brown, slightly lighter at gaster and apex of funiculus.

Type of A. rotundatus var. merwei are smoother, with dorsopropodeum, petiole and postpetiole at most alutaceus and propodeal reticulation feeble, almost smooth at some individuals.

Scattered decumbent white setae, shorter than petiole height, oriented backwards, present at head, dorsum of pronotum petiole, postpetiole and gaster. Dorsum of propodeum bare except for its posterior border, with 2–4 long erect setae. A few scattered, long, white, erect setae present at pronotum, petiole, postpetiole and gastral tergites, longer than petiole height.

Scapes with white unequally long semierect setae, clearly longer than scape width. No pubescence noted.

OTHER MATERIAL EXAMINED. KENYA: • Kajiado 11/01/1980 (Nyamaso, G.) (3w) [ NHMUK012849299 ] BMNH • same data (6 pins, 3w each) [ NHMUK012849300 to NHMUK012849305 ] BMNH • Rift Valley Province, Amboseli National Park 1144m, -2.8, 37.28 29/06/2002 (D. Martins). Acacia xanthophloea woodland (2w) [ CASENT0764136 ] FHGC • same data (3 pins, 3w each) [ CASENT0790560 to CASENT0790562 ] FHGC • Western Province, Kakamega Forest , Bukhaywa 1573m, 0.34581, 34.84806 01/07/2004. pitfall trap (F. Hita Garcia). farWLand near forest edge (3w), ground [ CASENT0217160 ] FHGC • Western Province, Kakamega Forest , Buyangu , nr. KWS village ( Kakamega ), 0.35, 34.85 02/08/2002 (M. Peeters) (3w) [ CASENT0790559 ] FHGC. NAMIBIA: • Otjiwarongo District, Okosongomingo Farm , 50 km ESE Otjiwarongo ( Kakamega ), -20.65, 17.083 16/11/1972 (C. L. Hogue) (1w) [ CASENT0790571 ] FHGC. SOUTH AFRICA: • CSFRI, Nelspruit 29/01/1990 (Samways, M. J.). Citrus orchard (1w) [ NHMUK012849255 ] BMNH • Mkuzi Res. ( Natal ) 02/06/1905 (Peeters, C.) (3w) [ NHMUK012849325 ] BMNH • same data (5 pins, 3w each) [ NHMUK012849262 to NHMUK012849266 ] BMNH. SUDAN: • Equatoria. Anglo-Egyptian Sudan 22/04/1905 (Weber) (2w) [ NHMUK012849260 ] BMNH. TANZANIA: • no loc 07/06/1984 (Minja, E.) (3w) [ NHMUK012849316 ] BMNH • same data (4 pins, 3w each) [ NHMUK012849317 to NHMUK012849320 ] BMNH. ZIMBABWE: • Bulawayo (Arnold) (2 pins, 2w each) MHNG, • same data (4 pins, 3w each) MHNG • Bulawayo iii.1912 (4W) NHMB • Bulawayo 01/01/1912 (Arnold, G.) (3 pins, 4w each) [ NHMUK012849257 to NHMUK012849259 ] BMNH • Bulawayo 17/11/1912 (Arnold, G.) (4w) [ NHMUK012849253 ] BMNH • Insuza Rd. 16/02/1939 (6w) [ NHMUK012849256 ] BMNH • Sawmills 01/05/1917 (Arnold) (5 pins, 1w each) [ MRACFOR000033 to MRACFOR000037 ] MRAC.

DISTRIBUTION. Southern and Eastern African, ranging from South Africa to Sudan (Fig. 58).

Figures

Fig. 56. Aenictus rotundatus, minor, syntype (CASENT0919641). A, head, dorsal view. B, habitus, lateral view. C, mesosoma, petiole and postpetiole, lateral view. D, mesosoma, petiole and postpetiole, dorsal view.

Fig. 57. Aenictus rotundatus, major worker (CASENT0249285). A, head, dorsal view. B, habitus, lateral view. C, mesosoma, petiole and postpetiole, lateral view. D, mesosoma, petiole and postpetiole, dorsal view.