Strumigenys nimbrata

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Strumigenys nimbrata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. nimbrata
Binomial name
Strumigenys nimbrata
Bolton, 1983

Strumigenys nimbrata casent0102150 profile 1.jpg

Strumigenys nimbrata casent0102150 dorsal 1.jpg

Specimen labels

Two collections records contain the only known clues regarding this ant's biology: littoral rainforest and primary forest litter-samples.

Identification

Bolton (1983) - A member of the nimbrata complex in the Strumigenys arnoldi-group. The size range of the non-paratypic material is HL 0.42-0.48, HW 0.31-0.37, CI 73-77, ML 0.17-0.21, MI 40-44, SL 0.22-0.26, SI 69-71. All this material matches the holotype. S. nimbrata is easily diagnosed by its very reduced funicular segments 2 and 3. Other characters aiding its recognition within the arnoldi-group include the cephalic pilosity, position of the proximal preapical teeth and size of the distals, development of the infradental lamellae and spongiform appendages, and minute size. The only other species sharing the character of very reduced funicular segments is Strumigenys bitheria, but in this species the flange bordering the upper scrobe margins is very broad, the distal preapical tooth of the mandible is longer, the pronotal dorsum has distinct punctate sculpture between the rugulae, the petiole node is as broad as long in dorsal view and the propodeal teeth are much longer than in nimbrata.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Gabon, Ghana, Ivory Coast (type locality).

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.

  • nimbrata. Strumigenys nimbrata Bolton, 1983: 381 (w.q.) IVORY COAST. See also: Bolton, 2000: 594.

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

Description

Worker

Holotype. TL 1.5, HL 0.43, HW 0.31, CI 72, ML 0.18, MI 42, SL 0.22, SI 71, PW 0.20, AL 0.37.

Outer margins of mandibles shallowly convex in full-face view, the blades narrowing basally and broadest at about the midlength. Apical fork of each mandible with 2 spiniform teeth, without intercalary teeth or denticles. Each mandible with 2 preapical teeth, a larger proximal tooth which is situated very close to the midlength of the blade, and a smaller distal preapical tooth which is close to the apical fork. The distance separating the bases of these two teeth is distinctly greater than the length of the distal preapical tooth. Upper scrobe margins with a narrow inconspicuous bordering rim or flange which is distinctly narrower than the maximum diameter of the eye. Eyes small, with only 4 ommatidia, the maximum diameter equal to or slightly less than the maximum width of the scape. Pre ocular notch absent, the ventral surface of the head without a pre ocular transverse groove or impression. Antennal scapes slender at the base and very weakly curved, the medial third slightly expanded and the leading edges with a row of apically curved narrow spoon-shaped hairs which are smaller than those fringing the upper scrobe margins. Funicular segments 2 and 3 vestigial and difficult to see, the separation of the two segments almost invisible and the length of segments 2 and 3 together less than half the length of segment 4 (the penultimate segment); under low magnification or in poor light the funiculus appears to consist of only 3 segments rather than the usual 5. Dorsum of head from posterior clypeal margin to about the midlength with conspicuous narrowly spoon-shaped pilosity which is curved anteriorly, and a double to triple row of these hairs border the upper scrobe margins. Behind the midlength the hairs are much smaller and sparser, narrow and inconspicuous; the pilosity of the two areas contrasting strongly. Dorsum of head with 6 standing hairs arranged in a transverse row of 4 close to the occipital margin and a more anteriorly situated pair. Dorsum of head reticulate-punctate. Pronotal humeri each with a single long fine flagellate hair. Mesonotum with a single pair of stout standing hairs. Ground-pilosity of dorsal alitrunk of sparse small hairs which are closely applied to the surface. Metanotal groove a feeble transverse line on the dorsum which is minutely impressed. Dorsum of mesonotum very shallowly concave in profile behind the level of the standing hairs, not sharply depressed. Propodeal teeth small and narrowly triangular, the infradental lamellae very narrow and petering out ventrally, broadest where they join the teeth. Sides of alitrunk unsculptured. Pronotal dorsum very weakly and irregularly longitudinally rugulose, the remainder of the dorsal alitrunk and the petiole node reticulate-punctate. Postpetiole smooth in centre of disc but elsewhere with faint superficial reticulation. Spongiform appendages of pedicel segments much reduced, the peduncle of the petiole with a narrow ventral strip and the lateral lobe of the node minute. Petiole node broader than long in dorsal view. Ventral spongiform lobe of postpetiole smaller than the exposed area of the postpetiolar disc in profile. Basigastral costulae widely spaced and short, but sharply defined. Petiole, postpetiole and gaster with stout standing hairs which are thickened apically. Colour dull yellow to brownish yellow.

Paratypes. TL 1.5-1.8, HL 0.42-0.46, HW 0.31-0.35, CI 72-77, ML 0.17-0.20, MI 40-45, SL 0.22-0.24, SI 68-73, PW 0.19-0.23, AL 0.35-0.43 (12 measured).

As holotype, the eyes with 4-6 ommatidia and the sculpture showing some variation in intensity. The postpetiole may be as described above, or wholly smooth, or even have a few faint longitudinal rugulae towards the outer edges of the disc.

Type Material

Holotype worker, Ivory Coast: Tai Forest, 17 .x.1980 (V Mahnert & J. -L. Perret) (Musee d'Histoire Naturelle Genève). Paratypes. 31 workers and 1 female with same data as holotype (MHNG; The Natural History Museum; Museum of Comparative Zoology; Ecole Nationale Superieure Agronomique).

References