Aenictus eugenii Emery, 1895

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 : 26-33

Aenictus eugenii Emery, 1895

( Figs 1 C , 11 A–D , 17 )

Aenictus eugenii EMERY, 1895 (w.):

17 Syntype, SOUTH AFRICA, [ CASENT0903759 , seen on web] ; Syntype A. eugenii , no loc. data (1w) MHNG [Examined].

Aenictus eugenii var. brazzai SANTSCHI, 1910: 355 (w.)

Syntype workers (3w), CONGO: Brazzaville 01.dec.1906 (Weiss) (3w) [ CASENT0911418 ] NHMB [Examined ]; Syntype, same data, (2 pins, 1w each) MHNG [Examined] ; Syntype, same data, (2 pins, 1w each) [ MRACFOR000016 , MRACFOR000017 ] MRAC [Examined ]; same data, not labelled as type (2w, 3w) NHMB [Examined] ; same data, not labelled as type (3w) [ EY19928 ] MNHN [Examined]. Syn. nov.

Aenictus brazzai Santschi ; SANTSCHI, 1924: 204 [Raised to species rank]. Syn. nov.

Aenictus eugenii subsp. caroli FOREL, 1910: 248 (w.)

Syntype, ERITREA: Nefassit (1w) NHMB [Examined] ; Syntype, Nefassit (Escherich) (1w) NHMB [Examined] ; Syntype, Erythraea (4w) (Escherich) NHMB [Examined] ; Syntype, Nefassit (Escherich) (3w) MHNG [Examined] , Syntype, same data (2w) [ CASENT0907026 ] MHNG [Examined] . Syn. nov.

Aenictus eugenii v. henrii SANTSCHI, 1924: 204 (w.)

Syntype, DEMOCRATIC REPUBLIC OF CONGO: Kidada ( Kitobola ) 14-25.ii.1922 (Dr. H. Schouteden) (1w) [ CASENT0911423 ] NHMB [Examined] ; Syntype, same data (15 pins, 1w each) [ MRACFOR000018 to MRACFOR000032 ] MRAC [Examined] . Syn. nov.

Aenictus eugeniae v. kenyensis SANTSCHI, 1933 (w.): 100 [Junior synonym of eugenii Gotwald & Cunningham-Van Someren, 1976: 183 , confirmed here];

Syntype, KENYA: Kiambou ( La Pelley ) (8w) [ CASENT0902686 ] NHMB [Examined] ; Syntypes, Liambu 27/02/1929 (R. H. Le Pelley) (3w each) [ NHMUK012849233 , NHMUK012849234 ] BMNH [Examined].

Aenictus eugenii Emery ; GOTWALD & CUNNINGHAM- VAN SOMEREN, 1976: 183 (Q.) KENYA.

DIAGNOSIS. Identification is straightforward due to the clypeal shape reduced to two teeth between the antennal sockets, its linear mandibles not closing against it and its long overall pilosity. Aenictus mvuvii sp. nov. shares the mandibular configuration but A. eugenii is larger, even in the minima workers (0.59<HW<0.89 vs. A. mvuvii 0.44<HW<0.59, 1.02<WL<1.40 vs. A. mvuvii 0.72<WL<0.91) with relatively longer scapes (69<SIL<83 vs. mvuvii 52<SIL<63) and presents long, unequal semierect to erect setae, while it’s adpressed in A. mvuvii .

DESCRIPTION ( Figs 1 C , 11 A–D ). WORKER HL: 0.71 [0.6-0.86]; HW: 0.71 [0.59-0.89]; SL: 0.53 [0.43-0.65]; WL: 1.18 [1.02-1.40]; PL: 0.27 [0.22-0.36]; PH: 0.22 [0.18-0.27]; PPL: 0.21 [0.18-0.26]; PPH: 0.19 [0.16-0.24]; CS: 0.71 [0.60-0.88]; CI: 99 [93-105]; SIL: 75 [69-83]; SIW: 75 [69-87]; WL/HW: 167 [154-187]; PI: 121 [104-134]; PPI: 107 [100-123]; CSR: 144; (n=42).

Scapes long, reaching three quarters of the head when laid back (SIL~75). All funicular segments elongate; the last four slightly widened but not becoming an apical club. Head subquadrate (CI~100), widest at mandibular base and narrowing to vertex, this a straight line and slightly shorter than the line at mandible insertions, with rounded corners.

Mandibles armed with one long sharp apical and one subapical tooth, followed by 5–7 denticles and sometimes a slightly larger basal tooth. Denticles and basal teeth become seriously eroded, seeming edentate.

Petiole subsessile with anterolateral and anterodorsal carinae present, dorsolateral and posterior carinae absent; propodeal dome rounded, rectangular, anteriorly almost tended and rounded, and posterior vertical face in lateral view, all angles rounded; in some individuals posterolateral petiolar corners angular, but without ridges. Postpetiole subrectangular with almost vertical anterior and posterior faces, the dorsal straight and horizontal, both angles rounded square; the anterior face slightly lower with a more tended rounded angle. Subpetiolar process always very developed, subrectangular, rounded and with a big rounded triangular lamella facing downwards, its whole size comparable to petiolar dome.

Head, pronotum (except its anterior declivity), dorsal surface of metanotum gaster, legs and dorsal surfaces of petiole and postpetiole glassy smooth. Mandibles finely rugulose; meso and metapleurae, propodeum, petiole and sides of postpetiole strongly reticulated; some (3-4) horizontal rugulae present at the lateropropodeum converging to the propodeal lobes; postpetiolar and in some individuals petiolar dorsum, smooth.

Body reddish brown to dark reddish brown, darker at mandibles and propodeum. Gaster and legs lighter, yellowish in some individuals.

Whole body with long, semierect to erect, sparse, white fine setae; semierect in funiculus, clearly longer than funiculus width; the rest with average size longer than petiole height; legs and gaster with semierect to decumbent setae, longer than femora width. No pubescence noted. DISCUSSION. This species seems to be the most widespread Afrotropical Aenictus , ranging from Ethiopia in the Northeast to South Africa. Samples from West Africa (Congo, RDC, Central African Republic) are quite intriguing, as no other species seems to share both habitats.

Arguments to sustain the synonymies proposed here are exposed below, but, given the wide distribution range exposed above, I do think that this species is the best candidate for a more detailed analysis on sibling species through molecular and genetic analysis.

ETHOLOGY. This species has been found attending Pseudococcus ( GOTWALD & CUNNINGHAM-VAN SOMEREN, 1976), second time in Dorylines.

SYNONYMS UNDER A. eugenii .

Aenictus brazzai Santschi, 1924 and all the described A. eugenii subspecies have been synonymized under A. eugenii in this revision. Morphometric analysis was performed to assess this decision.

Aenictus brazzai was described by SANTSCHI (1924), stating that the main difference with the A. eugenii type is the absence of clypeal teeth, being other differences its smaller size, and shorter funiculus segments and (‘above all’) also shorter head. Clypeal teeth are present in all the checked specimens of the A. brazzai type series ( Fig. 12C ); also head measurements fall into the lower third of all measured specimens, but without any significant difference with the minima workers of other samples.

Aenictus eugenii caroli was described by FOREL in 1910 as follows: “Head distinctly longer than broad, rear strongly narrowed as with the type. Antennae slimmer; the scape slightly overlaps the rear head quarter or reaches it well (does not reach it in the type). All the funicular segments much longer than thick, the shortest 1 1/2 times (shorter in type). The mesopleurae slightly matt and punctured. The petiole is barely longer than the second (longer in type). Body hair very long, as in rotundatus Mayr. Abdomen darker, more brownish-yellow (light yellowish with type). Otherwise, the propodeum and size are exactly the same as the type. Particularly striking is the shape of the head and antennae.”

GOTWALD & CUNNINGHAM- VAN SOMEREN (1976) refuses to give a verdict on its analysis of the A. eugenii species: “We have examined the types of carolli but are not prepared to deal with its status [...]. This subspecies is small and equal in size to the smallest eugenii specimens [...] While its pattern of punctuation is like that of eugenii , it is entirely golden yellow (the head and alitrunk of eugenii are reddish-brown)”

Shape of head (CI) doesn’t deviate from the pattern of the rest of the series ( Fig. 13 D , Fig. 14 C ). Scapes, though, seem to be slightly longer in the minima workers, but fall into the series again with larger workers ( Fig. 13 C , Fig. 14 B ). Morphometric analysis doesn’t show significant deviation from the population neither in head proportions/size nor in scape length nor in funicular segments, and measurements of the type series fall under all the size spectrum. The difference in colour cited by Gotwald may be due to being a recently hatched worker as other inspected workers in the type series also show the typical brown color on head and mesosoma.

Aenictus eugenii henrii was described by SANTSCHI (1924) as “Intermediate between the type and the var. caroli . Differs from this last for its head, less elongated and narrowed posteriorly, slightly shorter that the type. Differs from this by the clypeal teeth, closer, shaped as in caroli ”. The henrii type measurements and clypeal teeth show no significant deviation from the series.

SANTSCHI (1933) describes A. eugenii kenyensis as “[...]Differs from type by its shorter scapes not surpassing the upper quarter of the head. The first segment of funiculus longer. The rest like eugeniae ”. Scapes does not deviate from the series ( Figs 13 C , 14 B ).

Morphometric analysis does not reveal any difference among the different names implied in the problem and typical series for described subspecies appear to be a subset of the size diversity for the species ( Figs 13 , 14 ). The data used contain workers for each type series and one from Kare (Kenya), that stretches along all the size spectrum.

PCA ( Fig. 15 ) and NCCA ( Fig. 16 ) did not provide any evidence of separation among the different samples.

Based on these data, A. eugenii , A. brazzai, and all the A. eugenii subspecies seem to represent size subsets in the A. eugenii spectrum, so the synonymy among all of them is proposed.

OTHER MATERIAL EXAMINED. BOTSWANA: • Maxwee 19/05/1976 (Russell-Smith, A.) (2w) [ NHMUK012849236 ] BMNH • same data (3w each) [ NHMUK012849237 , NHMUK012849238 ] BMNH. BURUNDI: • Banage 08/06/1980 (Dejean, A.) (3w each) [ NHMUK012849239 , NHMUK012849240 ] BMNH. CENTRAL AFRICAN REPUBLIC: • Sangha-Mbaéré, Parc National Dzanga-Ndoki , Mabéa Bai , 21.4 km 53° NE Bayanga 510 m, 3.03333, 16.41 01-07/05/2001 (B.L. Fisher). rainforest (2w), ground forager(s) [ CASENT0415253 ] CASC • same data (3w) [ CASENT0415254 ] CASC • same data (1w) [ CASENT0415253 ] CASC. DEMOCRATIC REPUBLIC OF CONGO: • Sud-Kivu, Lwiro River , 47 km N. of Bukavu 1650 m, -2.21667, 28.83333 01/04/1958 (E.S. Ross, R.E. Leech) (3w each) [ CASENT0810230 , CASENT0810231 ] CASC • Rutshuru 01/1938 (H. J. Brédo) (54 pins 1w each) [ RBINSFOR002417 to RBINSFOR002470 ] RBINS. ERITREA: • Ghinda 28/03/1905 (Sett.) (1w) MHNG. ETHIOPIA: • Harar 1903 ( Bourg de Bozas ) (8 pins 1w each) [ EY19920 to EY19927 ] MNHN. KENYA: • Western Province, Kakamega Forest , Malawa Forest Fragment 1646m, 0.45, 34.85 01/07/2008. hand collected (F. Hita Garcia). rainforest (1w each), ground [ CASENT0790574 to CASENT0790579 ] FHGC • Rift Valley Province, Mpala Research Centre ( Laikipia ) 1600m, 0.29, 36.9 20/03/2001. hand collected (R.R. Snelling). Acacia xanthophloea woodland (3w), emerging from crack in concrete apron [ CASENT0790580 ] FHGC • Karen (Nairobi) 04/05/1972 (Cunningham, G. R.; Van Someren) (+10w, ethanol) [ FMNH-INS 0000 119 686 ] FMNH • same data 1w each [ FMNH-INS 0000 119 686-2 to FMNH-INS 0000 119 686-5 ] FMNH. MOZAMBIQUE: • Zambézia, Mount Mabu 375 m 26/03/2016 (B.L. Fisher et al.), rainforest (1w each), ex soil [ CASENT0779864 to CASENT0779866 ] CASC • same data ex soil [ CASENT0779876 to CASENT0779878 ] CASC • Zambézia, Mount Mabu 960 m 05/03/2016 (B.L. Fisher et al.). montane forest (1w each), sifted litter [ CASENT0782394 , CASENT0782395 ] CASC. SOUTH AFRICA: • Bothaville (1w) MHNG • Mpumalanga, Songimuelo NR, Kromdraai Camp. Komati River 800 m, - 26.04278, 31.00139 19/03/2001. Pitfalls (D. Ubick) (1w) [ CASENT0080142 ] CASC • Natal ( Wroughton ) (1w) MHNG • Orange Free State, Bothaville 01/06/1899 (Dr. Brauns) (1w) [ NHMUK012849226 ] BMNH • Orange Free State, Bothaville (G. Mayr) (1w) [ NHMUK012849235 ] BMNH • Free State, Bothaville (3 pins, 1w each) NMHW • Free State, Orange (1w) NMHW. UGANDA: • Bundibugyo, Semuliki National Park 685 m, 0.85681, 30.16672 01/08/2012 (B.L. Fisher et al.). rainforest (1w each), ground forager(s) [ CASENT0350547 to CASENT0350549 ] CASC • same data [ CASENT0350552 to CASENT0350554 ] CASC • Eastern Region, Mount Elgon N. P. 1859m, 1.38013, 34.4034. Pitfall (Vanderhaegen, K.). Shade coffee (1w) [ RBINSFOR000126 ] RBINS • Eastern Region, Mount Elgon N. P. 1410m, 0.88599, 34.31604. Litter Sieving + Winkler (Vanderhaegen, K.). Pine (1w) [ RBINSFOR001015 ] RBINS. ZIMBABWE: • Bulawayo (Arnold) (1w) NHMB • same data 08/02/1914 (1w each) [ NHMUK012849224 , NHMUK012849225 ] BMNH • same data (4w each) [ NHMUK012849227 to NHMUK012849230 ] BMNH • same data (1w) [ NHMUK012849232 ] • Bulawayo 01/01/1916 ( Arnold ) (1w each, 14 pin) [ MRACFOR000002 to MRACFOR000015 ] MRAC • Mope fountain 07/02/1921 ( Arnold , G.) (8w) [ NHMUK012849231 ] BMNH.

DISTRIBUTION. The species with the widest distribution in this revision. It ranges from Eritrea to South Africa in East Africa, but reaches the Western parts of Republic Democratic of Congo and the Central African Republic ( Fig. 17 ).

Figures

Fig. 1. Mandibular and clypeal shapes for the different species groups. A, gr. rotundatus (Aenictus guineensis, CASENT0876634). B, gr. koloi (Aenictus koloi, sp. nov., KGCOL00552). C, gr. eugenii (Aenictus eugenii, CASENT0235822). D, gr. eugenii (Aenictus mvuvii, sp. nov., CASENT0350555). E, gr. popeyei (Aenictus popeyei, sp. nov., CASENT0810234). F, gr. decolor (Aenictus decolor, CASENT0317077). G, gr. asantei (Aenictus asantei, NHMUK012849241). H, gr. rixator (Aenictus rixator, CASENT0907030).

Fig. 11. Aenictus eugenii, worker (CASENT0235822). A, head, dorsal view. B, habitus, lateral view. C, mesosoma, petiole and postpetiole, lateral view. D, mesosoma, petiole and postpetiole, dorsal view.

Fig. 17. Distribution of A. eugenii.

Fig.12. Type images of A. eugenii (A, head dorsal view, B, habitus lateral view) and its synonyms: A. brazzai (C, head dorsal view, D, habitus lateral view), A. eugenii caroli (E, head dorsal view, F, habitus lateral view), A. eugenii henrii (G, head dorsal view, H, habitus lateral view), and A. eugenii kenyensis (I, head dorsal view, J, habitus lateral view).

Fig. 13. Measurements for A. eugenii and its subspecies.

Fig. 14. Main indexes for A. eugenii and its subspecies.

Fig. 15. Principal Component Analysis (PCA) for A. eugenii and its subspecies.

Fig. 16. Nest Centered Cluster Analysis (NCCA) for A. eugenii and its subspecies.