Strumigenys dagon

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

The type material, 2 workers, were collected from forest humus.

Identification

A member of the Strumigenys dagon-group.

Bolton (1983) - G. dagon is immediately recognizable as no other African species has such short mandibles or such a bizarre clypeal structure. Its only close relative is Strumigenys sahura and the characters separating the two:

dagon	sahura
CI 70-71, MI 8-9.	CI 75-78, MI 16-17
Anterior clypeal margin with a deep median impression flanked on each side by a convex lobe.	Anterior clypeal margin shallowly concave.
Lateral free margins of clypeal lobes greatly thickened, thicker in profile than the maximum width of the scape.	Lateral free margins of clypeal lobes not thickened, in profile much narrower than the maximum width of the scape.
Lateral portions of postpetiolar disc smooth.	Lateral portions of postpetiolar disc finely sculptured.

Keys including this Species

Key to Afrotropical Strumigenys (as Pyramica)

Distribution

Distribution based on Regional Taxon Lists

Afrotropical Region: Rwanda (type locality).

Distribution based on AntMaps

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.

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.

Biology

Explore Overview of Strumigenys 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.

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Castes

Nomenclature

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

dagon. Glamyromyrmex dagon Bolton, 1983: 325, figs. 25, 32 (w.) RWANDA. Combination in Pyramica: Bolton, 1999: 1672; in Strumigenys: Baroni Urbani & De Andrade, 2007: 118. See also: Bolton, 2000: 297.

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 2.0, HL 0.57, HW 0.40, CI 70, ML 0.05, MI 9, SL 0.24, SI 60, PW 0.26, AL 0.52.

Mandibles appearing very short in full-face view (MI 8-9) as the apical (masticatory) margin is at a right-angle to the long axis of the head from the second tooth to the apex. Basal lamella of mandible, which is concealed by the clypeus at full closure, followed by a short diastema and a denticle. Distal to the denticle is a row of 5 large teeth which are slightly recurved, and apically two denticles which share a common base are present. In profile the upper mandibular margin curves upwards above the level of the anterior clypeal margin and the apical (masticatory) margin forms a near-vertical shallowly convex arch. Anterior clypeal margin in full-face view convex on each side of a deep median concavity, the lateral free margins of the clypeus expanded into a smoothly rounded prominent broad lobe on each side so that the outer margins of the closed mandibles intersect the anterior clypeal margin some distance medially of the anterolateral corners. Upper scrobe margins shallowly concave and feebly divergent posteriorly, the lateral margins of the occipital lobes behind this are shallowly convex and round behind into the smoothly concave occipital margin. In profile the edges of the laterally expanded clypeal lobes are greatly thickened in front of the level of the antennal insertions, the maximum thickness distinctly greater than the maximum width of the scape. Eyes present, small, situated on the ventral margin of the deep scrobe. Scapes of moderate length (SI 60), narrowly clavate and lacking projecting hairs on the leading edges. Dorsum of head with a single pair of erect fine hairs situated on each side of the midline close to the occipital margin. Otherwise the head only with very short fine simple hairs everywhere which are appressed and directed anteriorly; flagellate long hairs absent. Clypeus with scattered minute appressed pubescence only. Dorsum of clypeus, and of head in a band immediately behind the clypeus, glassy smooth. Remainder of cephalic dorsum finely and densely reticulate-punctulate. Anterior border of pronotum narrowly marginate, the sides of the pronotum immarginate anteriorly but separated from the dorsum by a blunt angle posteriorly. In profile the promesonotum dorsally forming a single convex outline which is separated from the propodeal dorsum by a small step, which appears as a transverse rim in dorsal view, the propodeum being on a slightly lower level than the mesonotum and marginate laterally. Infradental lamellae of propodeum broad, the propodeal teeth represented only by a short narrow denticle standing free of the lamella. Sides of alitrunk glassy smooth except for peripheral punctate sculpture. Pronotal dorsum unsculptured, mesonotum densely punctate, propodeum smooth anteriorly but with some punctures between the bases of the teeth.

Pronotum and mesonotum each with a single pair of long erect simple hairs, the dorsum otherwise only having scattered short appressed hairs which are directed roughly towards the midline. Spongiform appendages of pedicel segments massively developed in profile. Petiole node in dorsal view unsculptured, broader than long, flanked on each side by a prominent spongiform process, the two linked across the posterior margin of the node by a narrow lamella. Disc of postpetiole glassy smooth, very broad and surrounded by spongiform or lamellate tissue on all sides. Spongiform tissue broadest posterolaterally, narrowest medially where it is contracted down to a very narrow rim along the posterior margin of the disc. Base of first gastral tergite with a spongiform strip which is thickest laterally. Basigastral costulae sparse in centre of tergite, denser laterally. Dorsal surfaces of petiole, postpetiole and gaster with sparse erect simple pilosity and also with much shorter appressed widely scattered simple hairs. Colour yellowish brown.

Paratype. TL 2.1, HL 0.59, HW 0.42, CI 71, ML 0.05, MI 8, SL 0.25, SI 60, PW 0.28, AL 0.56. As holotype.

Type Material

Holotype worker, Rwanda: Rangiro, i.1976, forest humus, 1800 m (P. Werner) (Musee d'Histoire Naturelle Genève).

Paratype. 1 worker with same data as holotype (The Natural History Museum).

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. (page 325, figs. 25, 32 worker described)
Bolton, B. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). Journal of Natural History. 33:1639-1689. (page 1672, combination in Pyramica)
Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028. (page 297, figs. 201, 229 redescription of worker)

References based on Global Ant Biodiversity Informatics

Bolton B. 1983. The Afrotropical dacetine ants (Formicidae). Bulletin of the British Museum (Natural History). Entomology 46: 267-416.
Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65