Strumigenys helytruga

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

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Specimen Labels

Nothing is known about the biology of Strumigenys helytruga.

Identification

Bolton (2000) - A member of the Strumigenys scotti-group. Outer margins of mandibles strikingly straight, not at all convex, not at all bowed outwards. Eye small, with only about 8 ommatidia in total, the maximum eye diameter about equal to the maximum width of the scape. Preocular notch vestigially present, merely a feeble indentation in the ventrolateral margin immediately in front of the eye. Curved hairs that fringe upper scrobe margin narrowly spatulate, about the same size as those on leading edge of scape. Cephalic dorsum with a single pair of standing hairs, close to occipital margin; without a more anterior pair near highest point of vertex. First gastral tergite with stout standing hairs that are weakly remiform or thickened and bluntly rounded apically.

Bolton (1983) - S. helytruga is separated from its four close relatives (Strumigenys scotti, Strumigenys hastyla, Strumigenys murshila and Strumigenys zandala) by its retention of a vestigial preocular notch and relatively very small eyes. Of the five species only murshila has eyes which approach the small size seen in helytruga, but here the preocular notch is absent, the mandibles are conspicuously bowed outwards, the cephalic dorsum has six standing hairs, the postpetiole is sculptured and the distal preapical tooth of the left mandible is less than half the length of the proximal.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Angola (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.

  • helytruga. Strumigenys helytruga Bolton, 1983: 374 (w.) ANGOLA. See also: Bolton, 2000: 609.

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 2.2, HL 0.59, HW 0.43, CI 73, ML 0.29, MI 49, SL 0.34, SI 79, PW 0.26, AL 0.55.

In full-face view the mandibular blades approximately straight. Apical fork of each mandible with 2 spiniform teeth, without intercalary teeth or denticles. Preapical armament of 2 teeth on each blade, the proximal only fractionally longer than the distal and with both teeth situated in the apical third of the length of the blade. Upper scrobe margins evenly divergent posteriorly and without a bordering rim or flange, posteriorly grading evenly into the sides of the head. Preocular notch vestigially present, represented only by a feeble indentation of the ventrolateral margin immediately in front of the eye, the notch not extended onto the ventral surface of the head as a transverse groove or impression. Eye relatively small, about 0.12 X HW and with 8 ommatidia, the maximum diameter of the eye about equal to the maximum width of the scape or fractionally larger. Antennal scapes slender and roughly cylindrical, shallowly curved basally and with their leading edges equipped with a row of apically curved narrow spatulate hairs. Ground pilosity of head consisting of quite dense conspicuous spatulate hairs which are broader than those on the leading edges of the scapes. Upper scrobe margins without larger hairs but fringed with spatulate hairs the same size and shape as those on the dorsum. Elongate standing hairs on cephalic dorsum restricted to a single pair situated close to the midline near the occipital margin. Dorsum of head reticulate-punctate. Pronotal humeri each with a single fine flagellate hair. Mesonotum with a single pair of standing stout hairs. Ground-pilosity of dorsal alitrunk of sparse narrowly spatulate hairs. Posterior portion of mesonotum shallowly depressed behind the level of the hairs. Metanotal groove represented by a feebly impressed line. Propodeal teeth triangular and subtended by conspicuous infradentallamelIae. Sides of alitrunk mostly smooth but with some punctate sculpture dorsally and posteriorly. Pronotal dorsum longitudinally sparsely rugulose, with feeble superficial punctures between the rugulae. Mesonotum and propodeum densely punctate. Dorsum of petiole node punctate, the postpetiole smooth. In profile the petiole with a well-developed spongiform ventral strip and a narrow lateral lobe. Postpetiole with large ventral and lateral lobes. In dorsal view the petiole node with a broad posterior spongiform strip, the postpetiole with spongiform material projecting beyond the sides and posteriorly with a laminar transverse strip connecting the spongiform lateral lobes. Transverse basal strip of first gastral tergite laminar, the basigastral costulae arising from it sharply defined but sparse and short, with only 4 or 5 on each side of a central clear area. Petiole, postpetiole and gaster dorsally with stout standing hairs which are thickened apically. Colour dull brownish yellow.

Type Material

Holotype worker, Angola: Bruco, 26.ii.-2.iii.1972, forest litter (P. Hammond) (The Natural History Museum).

References