Aenictus bidentatus Donisthorpe, 1942

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 : 19-21

Aenictus bidentatus Donisthorpe, 1942 stat. rev.

( Figs 5 A–D , 6 )

Aenictus bidentatus DONISTHORPE, 1942: 701 (w.)

Holotype, GHANA: Tafo . ix-1940, ex. cocoa. Nº 1352 (G.S. Cotterell) (1w) [ BMNH(E)1015729 , CASENT0902685 ] BMNH [Examined]; Paratypes, same data (3w each) [ NHMUK012849178 , NHMUK012849179 ], BMNH [Examined]. [ Junior synonym of decolor: GOTWALD & LEROUX, 1980: 600]. Stat. rev.

DIAGNOSIS AND DISCUSSION. The three sibling species found in the decolor complex are almost identical in any morphological aspect except size and relative length of scapes. This fact led GOTWALD & LEROUX (1980) to propose the synonymy between A. batesi , A. bidentatus and A. decolor, although “the type specimens of A. decolor and batesi are larger than those of bidentatus , but in all other characteristics [...] appear identical” ( GOTWALD & LEROUX, 1980). Aenictus villiersi could also easily be included in the statement except for its poorly developed subpetiolar process.

Morphometrical analysis regarding SL and HL clearly separates the three species. Aenictus bidentatus is consistently smaller (0.54<HL<0.7) and with smaller scapes (63<SIL<76), while A. decolor is larger (0.7<HL<0.76) with much longer scapes (83<SIL<89). These two species present a developed subpetiolar process with lamella, while the third sibling species A. villiersi is similar in size to A. decolor, but with a small subpetiolar process and very long scapes (95<SIL<102).

DESCRIPTION ( Fig. 5 A–D ). WORKER HL: 0.61 [0.51-0.67]; HW: 0.59 [0.48-0.65]; SL: 0.43 [0.38-0.49]; WL: 0.96 [0.80-1.07]; PL: 0.23 [0.19-0.25]; PH: 0.18 [0.15-0.2]; PPL: 0.18 [0.15- 0.20]; PPH: 0.16 [0.13-0.18]; CS: 0.60 [0.50-0.65]; CI: 97 [91-103]; SIL: 70 [63-76]; SIW: 72 [64-80]; WL/HW: 162 [145-176]; PI: 122 [115-135]; PPI: 112 [100-128]; CSR: 131; (n=25).

With the characters defined for the decolor group and: scape long, surpassing three quarters of the head when laid back (SIL~88). Funicular segments 1–7 subquadrate, preapical longer than wide, apical more than twice longer than wide; the last three slightly widened but not becoming an apical club. Head subquadrate (CI~97), widest at distal third and narrowing to vertex, this a straight line and shorter than the line at mandible insertions.

Petiole subsessile with anterolateral and sometimes anterodorsal carina present, dorsolateral carina absent; propodeal dome rounded, “pushed” backwards, anteriorly sloping at approximately 45 degrees and almost vertical posterior face in lateral view, all angles rounded; sometimes petiole with anterior and dorsal faces straight, angles rounded. Postpetiole subrectangular with almost vertical anterior and vertical posterior faces, the dorsal straight and horizontal, both angles rounded square; the anterior face slightly lower with a more tended rounded angle. Subpetiolar process developed, subrectangular and without lamella, uncommonly a faint ridge or small lamella present.

Head, pronotum (except its anterior declivity), mesonotum gaster, scapes, legs and dorsal surfaces of petiole and postpetiole glassy smooth. Mandibles finely striated; meso and metapleurae strongly and irregularly rugulose especially at the mesopleurae; in some individuals mostly reticulated, but always some horizontal rugulae present at the lateropropodeum; dorsopropodeum finely rugulose; remainder of petiole and posteptiole alutaceus to faintly rugulose; surface between rugulae glossy.

Head and mesosoma reddish brown to dark reddish brown, especially at mandibles and propodeum. Gaster, coxae, legs and distal half of funiculus yellow to yellowish brown.

Whole body with long, sparse, white fine setae; decumbent to adpressed in scape, slightly longer than scape width, semierect in funiculus size about the funiculus width, decumbent setae at legs, size about femora width, erect to semierect in the rest of the body, unequal, the longest about petiole height. No pubescence noted.

DISTRIBUTION. West and Central Africa, from Ivory Coast to Cameroon, extending its range to the East in the forests of Uganda and Kenya ( Fig. 6 ).

OTHER MATERIAL EXAMINED. CAMEROON: • Pan Pan (Dejean, A.) (3w) [ BMNH(E)1018163 , CASENT0281966 ] BMNH • same data (3w each) [ NHMUK012849204 to NHMUK012849206 ] BMNH • Nkoemuon (Jackson, B.) (3w each) [ NHMUK012849194 to NHMUK012849196 ] BMNH . GHANA: • New Tafo C.R.I.G. 23/06/1979 (Gotwald, W.) (1w each) [ FMNH-INS 0000 053 987 to FMNH-INS 0000 053 995 ] FMNH • same data 26/06/1979 (1w) [ FMNH-INS 0000 053 999 ] FMNH. IVORY COAST: • Palmeraie Lame n 82 (Diomande, T.) (3w each) [ NHMUK012849186 to NHMUK012849193 ] BMNH . KENYA: • Western Province, Kakamega Forest, Lubao , Transect 5 1650m, 0.30372, 34.80444 20/06/2007. pitfall trap (G. Fischer). Intensively used tea field (1w) [ CASENT0217163 ] CASC • Western Province, Western Kenya Sugar Factory, Mwanza (Kakamega) 1650m, 0.37917, 34.82806 11/09/2007. pitfall trap (F. Hita Garcia). intensively used sugar cane plantation (1w), ground [ CASENT0790569 ] FHGC • Western Province, Kakamega Forest, Isecheno Forest Reserve , pumphouse (Kakamega) 1550m, 0.23, 34.86 07/05/2001, hand collected (R.R. Snelling). rainforest (1w), ex debris at base of tree [ CASENT0790570 ] FHGC. NIGERIA: • Black Pod Project (Taylor, B.). Cashew plot (2w) [ NHMUK012849181 ] BMNH; Gambari (Bolton, B.). On forest path (2w each) [ NHMUK012849182 to NHMUK012849185 ] BMNH • Ibadan (IITA) (Noyes, J.) (3w each) [ NHMUK012849197 to NHMUK012849203 ] BMNH . UGANDA: • Kabarole, Kibale National Park, Kanyawara Biological Station 1504 m, 0.55929, 30.35926 08/12/2012 (B.L. Fisher et al.). moist evergreen forest (1w each), ground forager(s) [ CASENT0350558 to CASENT0350560 ] CASC • Western, Kibale National Park, Kanyawara Biological Station (Kabarole) 1519 m, 0.56437, 30.35891 08/11/2012 (B.L.Fisher et al.). moist evergreen forest (1w each), ground nest [ CASENT0350561 , CASENT0350562 ] CASC • Kabarole Western, Kibale National Park, Kanyawara Biological Station 1510m, 0.56437, 30.36059 06/08/2012. hand collected (F. Hita Garcia); rainforest (1w each), ground [ CASENT0764139 , CASENT0790563 to CASENT0790568 ] FHGC .

Figures

Fig. 5. Aenictus bidentatus, worker (CASENT0350562). A, head, dorsal view. B, habitus, lateral view. C, mesosoma, petiole and postpetiole, lateral view. D, mesosoma, petiole and postpetiole, dorsal view.

Fig. 6. Distribution of A. bidentatus.