Aenictus eugenii

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Aenictus eugenii
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae
Genus: Aenictus
Species group: eugenii
Species: A. eugenii
Binomial name
Aenictus eugenii
Emery, 1895

Eugenii casent0415253 p 1 high.jpg

Eugenii casent0415253 d 1 high.jpg

Specimen Label

Synonyms
At a Glance • Ergatoid queen  

Santschi (1933) observed these ants tending Pseudococcus lilacinus, one of just a few rare records of an army ant associating with honeydew producing insects.

Identification

Gomez (2022) - A member of the Aenictus eugenii species group. 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 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. A. mvuvii 52<SIL<63) and presents long, unequal semierect to erect setae, while it’s adpressed in A. mvuvii.

Keys including this Species

Distribution

Latitudinal Distribution Pattern

Latitudinal Range: 15.3333° to -28.42192°.

   
North
Temperate 		North
Subtropical 		Tropical South
Subtropical 		South
Temperate

Distribution based on Regional Taxon Lists

Afrotropical Region: Botswana, Burundi, Central African Republic, Congo (type locality), Democratic Republic of Congo (type locality), Eritrea, Eswatini, Ethiopia (type locality), Kenya, Mozambique, South Africa (type locality), Uganda, Zimbabwe, Zimbabwe.

Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Countries Occupied

Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species.
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Estimated Abundance

Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species.
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Biology

Gotwald and Cunningham-van Someren (1976) - Aenictus eugenii Emery is distributed throughout much of East Africa, although it is not frequently seen. During the past 4 years we have encountered the species only 6 times, but on 4 of these occasions, we were able to observe, to some extent, the behavior of the species.

Foraging

Observations of A. eugenii colonies were limited to columns of worker ants traveling to or from their nests, usually discovered crossing footpaths where the hard-packed soil and absence of litter forced their exposure. The 4 colonies studied were observed at Karen (nr. Nairobi), Kenya and were designated: KC-081 (26 July 1971), KC-111 (4 May 1972), KC-112 (19 Sept. 1972), and KC-113 (28 March 1973). All columns were presumed to be foraging, either because the workers carried prey or because in the absence of prey they were not engaged in carrying their own brood.

Workers of colony KC-081 (discovered at 0930 hrs) moved along several anastomosing trails in tandem groups of 2 to 10 or more individuals. The workers moved in single file, and the tandem groups on any one trail were often widely separated from one another. Because different groups used the same trails at different times, it was obvious that the trails were chemical.

Colony KC-111 was detected as a foraging column, several meters in length, raiding the nest of an ant of the genus Pheidole. Several small columns branched from the main trunk, and some of the Aenictus workers encountered termite workers, which they ignored. A single myrmecophile was collected and was tentatively identified as Aenigmatopoeus sequax Borgmeier, a phorid fly that is also a predator of the driver ant Dorylus nigricans var. molesta (Kistner, personal communication).

Colony KC-112 was initially discovered at 0800 hrs (sky overcast, temperature 15.6°C) as a series of columns crossing a footpath and entering a flower garden. These columns branched from a base column of workers moving in single file, about 2 m long, that issued from a hole in the soil. At the end of each branch column, workers gathered, sometimes numbering in the hundreds, and proceeded to search an area approximately 30 cm square. The foraging workers moved swiftly in their search activity, and numerous workers returned along the original trail without evidence of booty. There were 5 to 7 such foraging groups which returned to the main column following completion of their search. The foraging activities of the column continued until 1200 hrs. One raiding group attacked a nest of Pheidole megacephala, and although they attacked individual Pheidole workers none were killed or taken as prey. One branch column of returning workers carried booty consisting of ant brood that was brought up from a hole in the soil, presumably the opening to the prey species nest. Of the 13 prey individuals taken from the foragers, 12 were pupae, 1 was a larva, and all were equal in size to the foraging workers. The prey species belonged to the subfamily Myrmicinae (probably Pheidole). Bengalia flies gathered about the raiding groups and occasionally stole prey from the Aenictus workers. The main column could not be traced back to the nest.

Colony KC-113 was discovered at 0830 hrs as a main foraging column returning to the nest with booty. At 1030 hrs it was still moving large numbers of prey. Curiously, this column was traveling on a well-worn trail of Dorylus nigricans var. molesta, and in fact, it passed directly over the active nest of this driver ant without conflict. Of the 286 prey units (whole individuals and/or pieces of individuals) collected from the returning foragers, all were ants or the subfamily Myrmicinae and all were imature forms. The prey units consisted of 101 whole larvae, 165 whole pupae, 7 pupal heads, 10 pupal gasters, 1 pupal alitrunk, and 2 pupae without heads. Of the 20 prey units that were pieces of pupae, 17 were from individuals that were obviously much larger than the Aenictus workers.

The foraging behavior of A. eugenii is like that of the West African species observed by Sudd (1959) and Gotwald (1975). The similarities are as follows: (1) workers commonly move in single file in small groups along the foraging trails; (2) A. eugenii is a specialized predator of ants, especially on the immature stages of ants of the subfamily Myrmicinae; (3) this species is a column raider, i.e. the terminal branches of a main foraging column each end in a small group of workers that search for and capture prey in a relatively small area; and (4) the foraging workers do not subdivide their prey before retrieval unless the prey individuals are larger than the foragers themselves.

Only two behavioral observations on A. eugenii appear in the literature. Arnold (1915) observed a group of workers "marching in single file and carring larvae from under one large stone to another" (although he failed to identify the column as foraging or emigrating), and Santschi (1933) noted that his type series for kenyensis (=eugenii) was attending a species of Pseudococcus. This latter observation implies that these workers were collecting honeydew, a behavior pattern recorded only once before for doryline ants (Arnold 1915).

Association with Other Organisms

Other Ants

Gotwald and Cunningham-van Someren (1976) observed this species attacking a nest of Pheidole megacephala, other Pheidole ants and carrying ant-brood along foraging trails leading back to their nest. Since there are few reported observations of Aenictus foraging, it is not known if A. eugenii, or any Aenictus, are myrmecophagous.

Other Insects

Explore-icon.png Explore: Show all Associate data or Search these data. See also a list of all data tables or learn how data is managed.
  • This species is a associate (details unknown) for the phorid fly Aenigmatopoeus sequax (a associate (details unknown) (Quevillon, 2018).

Castes

Known from the worker and queen caste. Table of castes known for all Afrotropical Aenictus species.

Worker

Gomez 2022, Figure 11.

Images from AntWeb

Aenictus brazzai casent0911418 h 1 high.jpgAenictus brazzai casent0911418 p 1 high.jpgAenictus brazzai casent0911418 d 1 high.jpgAenictus brazzai casent0911418 l 1 high.jpg
Syntype of Aenictus brazzai. Worker. Specimen code casent0911418. Photographer Will Ericson, uploaded by California Academy of Sciences. Owned by NHMB, Basel, Switzerland.

Queen

  • Figure 1A-B. Ergatoid queen of A. eugenii. From Gotwald & Cunningham-van Sommeren 1976.
  • Gotwald & Cunningham-van Sommeren 1976. Figure 1C-E. External morphology of the queen of Aenictus eugenii, pilosity omitted: (C) petiolar node, dorsal aspect; (D) petiolar node, lateral aspect; (E) head, dorsal aspect. Ergatoid queen of A. eugenii.

Nomenclature

The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.

  • eugenii. Aenictus eugenii Emery, 1895h: 17, pl. 2, figs. 1-4 (w.) SOUTH AFRICA.
    • Type-material: holotype worker.
    • Type-locality: South Africa: Makapan, i.-iv.1893 (E. Simon).
    • Type-depository: MSNG.
    • [Note: Gómez, 2022: 26, cites 1w syntype MHNG, but Emery, 1895h: 18, states that only a single specimen was present.]
    • [Misspelled as eugeniae by Arnold, 1915: 139, and others.]
    • Gotwald & Cunningham-Van Someren, 1976: 183 (q.).
    • Status as species: Emery, 1895j: 747; Wasmann, 1904b: 676; Emery, 1910b: 31; Forel, 1911e: 255; Arnold, 1915: 139 (redescription); Wheeler, W.M. 1922a: 752; Prins, 1963: 97; Gotwald & Cunningham-Van Someren, 1976: 183; Bolton, 1995b: 59; Hita Garcia, et al. 2013: 201; Gómez, 2022: 26 (redescription).
    • Senior synonym of brazzai: Gómez, 2022: 26.
    • Senior synonym of caroli: Gómez, 2022: 26.
    • Senior synonym of henrii: Gómez, 2022: 26.
    • Senior synonym of kenyensis: Gotwald & Cunningham-Van Someren, 1976: 183; Bolton, 1995b: 59; Gómez, 2022: 26.
    • Distribution: Botswana, Burundi, Central African Republic, Congo, Democratic Republic of Congo, Eritrea, Ethiopia, Kenya, Mozambique, South Africa, Uganda, Zimbabwe.
    • Current subspecies: nominal plus caroli, henrii.
  • brazzai. Aenictus eugenii var. brazzai Santschi, 1910c: 355 (w.) CONGO.
    • Type-material: syntype workers (number not stated).
    • [Notes (i): Baroni Urbani, 1977e: 67, cites 11w syntypes NHMB; (ii) Gómez, 2022: 26, cites 3w syntypes MNHN from type-series, but not labelled as types.]
    • Type-locality: Congo (“Congo français”): Brazzaville, 1.xii.1906 (A. Weiss).
    • Type-depositories: MHNG, MNHN, MRAC, NHMB.
    • Subspecies of eugenii: Wheeler, W.M. 1922a: 752.
    • Status as species: Santschi, 1924b: 204; Bolton, 1995b: 59.
    • Junior synonym of eugenii: Gómez, 2022: 26.
  • caroli. Aenictus eugenii subsp. caroli Forel, 1910c: 248 (w.) ERITREA.
    • Type-material: syntype workers (number not stated).
    • [Notes (i): Baroni Urbani, 1977e: 67, cites 2w syntypes NHMB; (ii) Gómez, 2022: 26, cites 5w syntypes MHNG; (iii) Radchenko, Fisher, et al. 2023: 12, cite 13w syntypes SIZK.]
    • Type-locality: Eritrea: Nefassit, 1906 (K. Escherich).
    • Type-depositories: MHNG, NHMB, SIZK.
    • Subspecies of eugenii: Wheeler, W.M. 1922a: 752; Finzi, 1939a: 162; Bolton, 1995b: 59; Madl, 2019: 13.
    • Junior synonym of eugenii: Gómez, 2022: 26.
  • henrii. Aenictus eugenii var. henrii Santschi, 1924b: 204 (w.) DEMOCRATIC REPUBLIC OF CONGO.
    • Type-material: 16 syntype workers.
    • [Notes (i): Baroni Urbani, 1977e: 67, cites 4w syntypes NHMB; (ii) Gómez, 2022: 26, cites 15w syntypes MRAC.]
    • Type-locality: Democratic Republic of Congo (“Congo belge”): Kidada, nr Kitobola, 14-25.ii.1922 (H. Schouteden).
    • Type-depositories: MRAC, NHMB.
    • Subspecies of eugenii: Bolton, 1995b: 59.
    • Junior synonym of eugenii: Gómez, 2022: 26.
  • kenyensis. Aenictus eugeniae var. kenyensis Santschi, 1933b: 100 (w.) KENYA.
    • Type-material: syntype workers (number not stated).
    • [Note: Baroni Urbani, 1977e: 67, cites 15w syntypes NHMB.]
    • Type-locality: Kenya: Kiambou, 27.ii.1929, no. 180, attending Pseudococcus lilacinus (R.H. Le Pelley).
    • Type-depositories: BMNH, NHMB.
    • Junior synonym of eugenii: Gotwald & Cunningham-Van Someren, 1976: 183; Bolton, 1995b: 60; Gómez, 2022: 26.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

  • Emery 1895i, page 17.
  • Emery 1895i, page 18.

Gomez (2022) - 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.

Queen

Gotwald and Cunningham-van Someren (1976) - Total length 10.55 mm, head length 1.53 mm, head width 1.62 mm, cephalic index 106, alitrunk length 2.20 mm, petiole length 0.72 mm, gaster length 6.10 mm, scape length 0.72 mm, length of petiolar node 0.67 mm, width of petiolar node 0.90 mm, hind femur length 1.35 mm, mandible length (from point of insertion to tip of apical tooth) 0.81 mm.

Head, alitrunk, petiole, gaster and appendages reddishbrown. Darkest on mandibles and dorsum and venter of gaster.

Head sutureless, without eyes, punctation or frontal carinae. Occipital margin medially concave. Antennal fossae deeply impressed. Clypeus medially emarginate, without teeth or other distinguishing characteristics. Antenna 10-segmented; scape short.

Alitrunk without conspicuous sutures or punctation. Meso- and metathoracic spiracles form raised, tubercle-like structures; propodeal spiracle conspicuous but not elevated. Distal margin of bulla covering metapleural gland orifice conspicuous, parallel to the longitudinal axis of the body and located directly beneath the propodeal spiracle. Declivity of the propodeum slightly concave.

Petiole. Posterior lateral angles prominent; posterior third of petiolar dorsum smoothly concave between angles. Anterior margin of node, in dorsal view, concave. Subpetiolar process prominent, triangular, and directed caudally.

Integument of gaster without conspicuous punctation. Gaster with 5 visible segments; tergite of 5th segment deeply notched medially along the posterior margin. Tip of ovipositor (?) conspicuous.

Entire body shiny, without conspicuous punctation. Pubescence yellow, sparse, and most conspicuous in small patches on anterolateral angles of head, the mandibles, antennae, legs, and posterior margins of gastral sclerites; groups of setae elsewhere on pronotum, propodeum and petiole. Tarsal claws simple.

Type Material

  • Aenictus eugenii
    • Syntype worker, SOUTH AFRICA, [CASENT0903759, seen on web]; Syntype A. eugenii, no loc. data (1w) MHNG [Examined by Gomez, 2022].
  • Aenictus eugenii brazzai
    • Syntype workers (3w), CONGO: Brazzaville 01.dec.1906 (Weiss) (3w) [CASENT0911418] NHMB [Examined by Gomez, 2022]; Syntype, same data, (2 pins, 1w each) MHNG [Examined by Gomez, 2022]; Syntype, same data, (2 pins, 1w each) [MRACFOR000016, MRACFOR000017] MRAC [Examined by Gomez, 2022]; same data, not labelled as type (2w, 3w) NHMB [Examined by Gomez, 2022]; same data, not labelled as type (3w) [EY19928] MNHN [Examined by Gomez, 2022].
  • Aenictus eugenii caroli
    • Syntype worker, ERITREA: Nefassit (1w) NHMB [Examined by Gomez, 2022]; Syntype, Nefassit (Escherich) (1w) NHMB [Examined by Gomez, 2022]; Syntype, Erythraea (4w) (Escherich) NHMB [Examined by Gomez, 2022]; Syntype, Nefassit (Escherich) (3w) MHNG [Examined by Gomez, 2022], Syntype, same data (2w) [CASENT0907026] MHNG [Examined by Gomez, 2022].
  • Aenictus eugenii henrii
    • Syntype worker, DEMOCRATIC REPUBLIC OF CONGO: Kidada (Kitobola) 14-25.ii.1922 (Dr. H. Schouteden) (1w) [CASENT0911423] NHMB [Examined by Gomez, 2022]; Syntype, same data (15 pins, 1w each) [MRACFOR000018 to MRACFOR000032] MRAC [Examined by Gomez, 2022].
  • Aenictus eugeniae kenyensis
    • Syntype worker, KENYA: Kiambou (La Pelley) (8w) [CASENT0902686] NHMB [Examined by Gomez, 2022]; Syntypes, Liambu 27/02/1929 (R. H. Le Pelley) (3w each) [NHMUK012849233, NHMUK012849234] BMNH [Examined by Gomez, 2022].

References

References based on Global Ant Biodiversity Informatics

  • Arnold G. 1915. A monograph of the Formicidae of South Africa. Part I. Ponerinae, Dorylinae. Annals of the South African Museum 14: 1-159.
  • Baroni Urbani C. 1977. Katalog der Typen von Formicidae (Hymenoptera) der Sammlung des Naturhistorischen Museums Basel (2. Teil). Mitt. Entomol. Ges. Basel (n.s.) 27: 61-102.
  • Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.
  • Forel A. 1911. Die Ameisen des K. Zoologischen Museums in München. Sitzungsber. Math.-Phys. Kl. K. Bayer. Akad. Wiss. Münch. 11: 249-303.
  • Gotwald W. H., Jr.; Cunningham-van Someren, G. R. 1976. Taxonomic and behavioral notes on the African ant, Aenictus eugenii Emery, with a description of the queen (Hymenoptera: Formicidae). Journal of the New York Entomological Society 84:182-188.
  • Gotwald, W. H., Jr.; Cunningham-van Someren, G. R. 1976. Taxonomic and behavioral notes on the African ant, Aenictus eugenii Emery, with a description of the queen (Hymenoptera: Formicidae). Journal of the New York Entomological Society 84:182-188.
  • Hita Garcia F., E. Wiesel, G. Fischer. 2013. The ants of Kenya (Hymenoptera: Formicidae)—faunal overview, first species checklist, bibliography, accounts for all genera, and discussion on taxonomy and zoogeography. Journal of East African Natural History 101: 127-222.
  • IZIKO South Africa Museum Collection
  • Prins A. J. 1963. A list of the ants collected in the Kruger National Park with notes on their distribution. Koedoe 6: 91-108.
  • Prins A. J. 1964. Revised list of the ants collected in the Kruger National Park. Koedoe 7: 77-93.
  • Santschi F. 1910. Formicides nouveaux ou peu connus du Congo français. Annales de la Société Entomologique de France 78: 349-400.
  • Santschi F. 1933. Contribution à l'étude des fourmis de l'Afrique tropicale. Bulletin et Annales de la Société Entomologique de Belgique. 73: 95-108.
  • Ward P. S. 2007. The ant genus Leptanilloides: discovery of the male and evaluation of phylogenetic relationships based on DNA sequence data. Memoirs of the American Entomological Institute 80: 637-649.
  • Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. VIII. A synonymic list of the ants of the Ethiopian region. Bulletin of the American Museum of Natural History 45: 711-1004
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