Strumigenys kerasma

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

Pyramica kerasma casent0102548 profile 1.jpg

Pyramica kerasma casent0102548 dorsal 1.jpg

Specimen labels

Known mostly from rainforest litter-samples, with an additional record from a montane forest.

Identification

A member of the Strumigenys weberi-group.

Bolton (1983) - Among the nine species of this group which have the postpetiole unsculptured only three (kerasma, Strumigenys mekaha, Strumigenys weberi) have the metanotal groove impressed. S. kerasma and mekaha differ together from weberi as follows.

kerasma and mekaha weberi
Median indentation of posterior spongiform appendage of postpetiole shallow, not approaching the margin of the disc. Median indentation of posterior spongiform appendage of postpetiole reaching the margin of the disc.
Spongiform material bordering margin of postpetiole posteriorly as wide from front to back as the disc of the postpetiole is long. Spongiform material bordering margin of postpetiole posteriorly distinctly narrower from front to back than the disc of the postpetiole is long.
Propodeal teeth long, the infradental lamella vestigial and its free margin evenly concave. Propodeal teeth short and broad, the infradental lamella conspicuous and its free margin straight or feebly sinuate, not evenly concave.
All hairs on dorsum of head of same construction and approximate size, not divided into appressed small ground-pilosity and much larger erect subclavate hairs. Hairs on dorsum of head of two forms, divided into small appressed ground-pilosity and much larger erect subclavate hairs.
Larger species, HL 0.68-0.70 HW 0.44-0.47. Smaller species, HL 0.61, HW 0.39.
Second tooth of principal mandibular row the longest, the first (basalmost) and third about equal in length. Second tooth of principal mandibular row the longest but the first (basalmost) very much smaller than the third.

S. kerasma and mekaha are a very closely related pair but are quickly separated by the form of the cephalic pilosity. In kerasma the principal cephalic hairs are erect or suberect basally but pass through an obtuse angle so that their apical halves are directed anteriorly. In mekaha the cephalic hairs lack this structure, instead being evenly arched forward from base to apex, their apices generally in contact with the surface of the head some distance in front of their point of origin.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Cameroun (type locality), Gabon.

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.

  • kerasma. Smithistruma kerasma Bolton, 1983: 303, fig. 16 (w.) CAMEROUN. Combination in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 122. See also: Bolton, 2000: 338.

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 25, HL 0.68, HW 0.44, CI 65, ML 0.06, MI 9, SL 0.30, SI 68, PW 0.32, AL 0.69.

Mandibular dentition (from a paratype) consisting of a high truncated rectangular basal lamella with concave sides, followed by a small diastema and a principal row of 5 relatively large teeth. Distal to this with 2 slightly smaller teeth, 4 minute denticles and a small apical tooth. Anterior clypeal margin broadly shallowly convex, sides of the clypeus irregular and only very weakly convergent anteriorly to the rounded anterolateral angles. Preocular laminae weakly convex in full-face view, the lateral margins of the head rugular and uneven. Lateral margins of clypeus in full-face view with a few simple anteriorly curved short hairs and with longer stouter simple hairs which project anterolaterally from the margin and are curved upwards. Sides of head with abundant fine simple projecting hairs which are curved anteriorly in their apical halves. Hairs on clypeal dorsum fine, more or less vertical and curved towards the midline. Dorsum of head with abundant fine simple hairs which are erect or sub erect basally but which are angled anteriorly in their apical halves, those situated more posteriorly on the dorsum being in general more strongly bent forward than those situated more anteriorly. The most strongly bent hairs are inverted L-shaped. All hairs on dorsal head approximately the same size and stature, without hairs which are obviously longer and stouter than others. Dorsum of head coarsely irregularly reticulate-rugose, the clypeus similarly but less intensely sculptured. Antennal scapes scarcely bent basally, broadest at about the midlength and the leading edge with projecting curved simple hairs which also occur on the dorsum of the scape. Maximum diameter of eye 0.16 X HW. Pronotum not marginate laterally, without a median longitudinal ridge or carina dorsally. In profile the alitrunk with the mesonotum strongly convex, sloping down posteriorly to a broad, shallow but distinctly impressed metanotal groove. Dorsal outline of propodeum raised behind the metanotal groove, then sloping downwards to the triangular propodeal teeth. Infradental lamellae of propodeum vestigial, their free margins strongly concave. Pronotal and mesonotal dorsa with numerous erect to suberect long fine simple hairs which are bent in their apical halves and often directed anteriorly. Dorsal surfaces of petiole, postpetiole and gaster with elongate simple hairs which are sub flagellate to flagellate or sometimes arched over. Dorsal (outer) surfaces of middle and hind tibiae with projecting simple subflagellate hairs. Sides of pronotum and propodeum coarsely rugose, the pleurae punctate; the punctures of the mesopleuron smaller denser and more sharply defined than those on the metapleuron. Pronotal dorsum coarsely longitudinally rugose, the rugae broad and high and the spaces between them smooth. Mesonotum, metanotal groove and base of propodeal dorsum strongly rugose but the rugae less massive and less regular than on the pronotum. Central area of propodeal dorsum with irregular punctures, declivity smooth. Petiole dorsum coarsely rugose, postpetiole dorsum smooth and shiny. First gastral tergite unscuJptured except for the regular strong short basal costulae. With pedicel segments in profile the spongiform appendages massively developed. In dorsal view the posterior margin of the petiole with a very broad spongiform strip which has its free posterior margin shallowly concave medially and which is broadest posterolaterally where its length is equal to that of the free side of the node in front of it. Disc of postpetiole thickly surrounded by spongiform material on all sides in dorsal view. The broadly and shallowly concave anterior margin of the postpetiole is equipped with a thick ruff-like transverse spongiform band which is contiguous with the lateral spongiform material on each side. Convex posterior margin of postpetiolar disc indented medially and bearing an extremely broad spongiform band whose posterior margin is also indented medially. The spongiform material on each side of the median indentation is as broad as the disc is long. Base of first gastral tergite with a thick spongiform ruff from which the basigastral costulae emerge. Colour dark brown.

Paratypes. TL 2.5-2.6, HL 0.68-0.70, HW 0.44-0.45, CI 64-66, ML 0.06-0.07, MI 9-10, SL 0.30-0.31, SI 68-70, PW 0.32-0.33, AL 0.68-0.72 (9 measured). As holotype.

Type Material

Holotype worker, Cameroun: Nkoemvon, 16.iii.1980 (D. Jackson) (The Natural History Museum). Paratypes. 9 workers with same data as holotype (BMNH; Musee d'Histoire Naturelle Genève; Museum of Comparative Zoology; Ecole Nationale Superieure Agronomique).

References