Strumigenys marginata

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Strumigenys marginata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. marginata
Binomial name
Strumigenys marginata
(Santschi, 1914)

Pyramica marginata casent0178314 profile 1.jpg

Pyramica marginata casent0178314 dorsal 1.jpg

Specimen labels

Known from numerous habitats, the still meager number of records of this species have all been collected from litter samples.

Identification

Bolton (2000) – A member of the Strumigenys marginata-group. The two known species of the group are easily separated. S. marginata: Antenna with 4 segments. Pronotum with sharp raised lateral marginations, Dorsal alitrunk unsculptured except for median carina. HW 0.25-0.30; MI 8-10; SI 64-67. Strumigenys rusta: Antenna with 6 segments. Pronotum without sharp raised lateral marginations. Dorsal alitrunk punctate to reticulate-punctate at least on mesonotum. HW 0.36-0.38; MI 12-14; SI 70-78.

Bolton (1983) - One of the few Smithistruma (= Strumigenys) species to have 4-segmented antennae, marginata is separated from all others with this antennomere count by the shape of its clypeus and lack of clypeal pilosity, by its strongly marginate pronotum and possession of a median longitudinal ridge or carina on the pronotal dorsum.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Ghana, Ivory Coast, Kenya (type locality), South Africa, United Republic of Tanzania, Zimbabwe.


Distribution based on AntMaps

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Distribution based on AntWeb specimens

Check data from AntWeb

Biology

Strumigenys were once thought to be rare. The development and increased use of litter sampling methods has led to the discovery of a tremendous diversity of species. Many species are specialized predators (e.g. see Strumigenys membranifera and Strumigenys louisianae). Collembola (springtails) and other tiny soil arthropods are typically favored prey. Species with long linear mandibles employ trap-jaws to sieze their stalked prey (see Dacetine trap-jaws). Larvae feed directly on insect prey brought to them by workers. Trophallaxis is rarely practiced. Most species live in the soil, leaf litter, decaying wood or opportunistically move into inhabitable cavities on or under the soil. Colonies are small, typically less than 100 individuals but in some species many hundreds. Moist warm habitats and micro-habitats are preferred. A few better known tramp and otherwise widely ranging species tolerate drier conditions. Foraging is often in the leaf litter and humus. Workers of many species rarely venture above ground or into exposed, open areas. Individuals are typically small, slow moving and cryptic in coloration. When disturbed individuals freeze and remain motionless. Males are not known for a large majority of species.

Castes

Nomenclature

The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • marginata. Epitritus marginatus Santschi, 1914b: 114, fig. 21 (w.q.) KENYA. Combination in Miccostruma: Brown, 1948e: 123; in Smithistruma: Bolton, 1983: 312; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 123. See also: Bolton, 2000: 320.

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

Description

Worker

Bolton (1983) - TL 1.2-1.3, HL 0.40-0.43, HW 0.26-0.28, CI 64-68, ML 0.04, MI 8-10, SL 0.17-0.18, SI 64-67, PW 0.16-0.18, AL 0.37-0.39 (10 measured).

Mandible with a low basal lamella, not a high triangle or high rectangle with concave sides, the lamella not or just visible when the mandibles are closed. No diastema between basal lamella of mandible and basal most tooth. Principal dental row consisting of 7 teeth, followed by 4 minute denticles and a small apical tooth. In full-face view the outer margins of the fully closed mandibles diverging posteriorly but intersecting the shallowly convex anterior margin of the clypeus well in from the rounded anterolateral angles; the outer margins of the mandibles and the lateral clypeal margins not forming a more or less continuous line. Clypeus absolutely devoid of hairs, without fringing pilosity and lacking dorsal pilosity. Lateral margins of clypeus straight and parallel, rounding anteriorly into the shallowly convex anterior margin, continuous posteriorly with the parallel preocular laminae. Disc of clypeus without a tumulus, with scattered minute pubescence visible under high magnification and with its posteriormost portion slightly raised into a low blunt prominence between the frontal lobes. Upper scrobe margins in full-face view evenly curved-divergent behind the frontal lobes, with a maximum of three laterally projecting flagellate hairs on each side, though these seem to be lost easily by abrasion. Dorsum of head with very fine sparse simple curved short ground-pilosity and with two pairs of long curved to flagellate hairs. Dorsum of clypeus finely shagreened or granular, dorsum of head finely reticulate-punctate. Antennae with 4 segments, the scapes curved in the basal third, not dorsoventrally flattened beyond the curve; their leading edges with fine apically curved simple hairs which are decumbent to appressed. Eyes small, their maximum diameter only about 0.07 X HW and distinctly less than the maximum width of the scape. Pronotum sharply marginate anteriorly and laterally and with a strong mid-dorsal longitudinal ridge or carina which may be doubled for part or most of its length. Mesonotum laterally less strongly marginate than pronotum but propodeum sharply marginate to the base of the teeth. Mesonotal dorsum usually with a continuation of the pronotal median carina but this may be poorly developed or faint in some individuals. The dorsal alitrunk with a transverse crest or slightly raised step between the mesonotum and propodeum. Dorsal alitrunk with scattered sparse ground-pilosity which is short fine and decumbent, and with three pairs of flagellate hairs distributed as follows. First pair on pronotal humeri, directed dorsolaterally; second pair at approximate mid length of lateral pronotal margination, directed dorsally; third pair on mesonotal margin posteriorly, close to the transverse crest, directed dorsally. Propodeal teeth laminar and continuous with the broad infradental lamellae which run the length of the declivity on each side. Sides of alitrunk unsculptured. Pronotal dorsum mostly smooth but in some with the faintest vestiges of patchy superficial sculpture. Mesonotum posteriorly with faint vestiges of reticular sculpture; propodeum smooth. Spongiform appendages of petiole and postpetiole strongly developed and very voluminous in profile, but in dorsal view only the posterior margin of each segment bounded by spongiform tissue and on the postpetiole the transverse spongiform material is interrupted posteromedially. Disc of postpetiole unsculptured, its posterior margin slightly indented medially. Both pedicel segments with fine curved hairs, some of which are long and subflagellate. First gastral tergite with 5 or 6 basigastral costulae on each side of the midline, otherwise the gaster unsculptured. Gastral pilosity simple and sparse, consisting of scattered fine short hairs which are decumbent to appressed and even sparser suberect to erect fine hairs which are longer. Legs with appressed pubescence only, without standing hairs. Colour uniform dull yellow to yellowish brown.

Type Material

Bolton (2000) - Syntype workers and queen, KENYA: Shimoni, st. no. 9, xi.1911 (Ch. Alluaud & R. Jeannel) (Naturhistorisches Museum, Basel, Musee National d'Histoire Naturelle) [examined].

References

  • Baroni Urbani, C. & De Andrade, M.L. 2007. The ant tribe Dacetini: limits and constituent genera, with descriptions of new species. Annali del Museo Civico di Storia Naturale “G. Doria” 99: 1-191.
  • Bolton, B. 1983. The Afrotropical dacetine ants (Formicidae). Bulletin of the British Museum (Natural History). Entomology. 46:267-416. PDF (page 312, redescription of worker, Combination in Smithistruma)
  • Bolton, B. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). Journal of Natural History. 33:1639-1689. (page 1673, combination in Pyramica)
  • Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028. (page 320, figs. 211, 234 redescription of worker)
  • Brown, W. L., Jr. 1948e. A preliminary generic revision of the higher Dacetini (Hymenoptera: Formicidae). Trans. Am. Entomol. Soc. 74:101-129. (page 123, combination in Miccostruma)
  • Donisthorpe, H. 1916b. Epitritus wheeleri, n. sp., an ant new to science; with notes on the genus Epitritus, Emery. Entomol. Rec. J. Var. 28:121-122. (page 122, catalogue)
  • Emery, C. 1924f [1922]. Hymenoptera. Fam. Formicidae. Subfam. Myrmicinae. [concl.]. Genera Insectorum. 174C:207-397. (page 327, catalogue)
  • Santschi, F. 1914b. Voyage de Ch. Alluaud et R. Jeannel en Afrique Orientale, 1911-1912. Résultats scientifiques. Insectes Hyménoptères. II. Formicidae. Paris: Libr. A. Schulz, pp. 41-148. (page 114, fig. 21 worker, queen described)
  • Wheeler, W. M. 1922j. 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. Bull. Am. Mus. Nat. Hist. 45:711-1004. (page 921, catalogue)