Strumigenys chilo

Strumigenys chilo
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Hymenoptera
Family:	Formicidae
Subfamily:	Myrmicinae
Tribe:	Attini
Genus:	Strumigenys
Species:	S. chilo
Binomial name
Strumigenys chilo Fisher, 2000 Specimen labels

Widely distributed in Madagascar rain forests, it occurs in other wet forest habitats as well. In addition to the many samples collected from litter samples, S. chilo has been found in downed logs and wood.

Identification

Bolton (2000) - A member of the chilo complex in the Strumigenys grandidieri-group. S. chilo is widely distributed in Madagascar rain forests and forms a close species pair with Strumigenys bibiolona within the grandidieri-group. They both have the mandibular apical fork subtended by a shorter third tooth, and the scrobe margin does not extend across the dorsal apex of the preocular groove so that the latter extends uninterrupted to the cephalic dorsum.

S. chilo is easily differentiated from bibiolona by the following characters: 1. Dorsum of head sharply depressed behind middorsum, forming a very shallow concave impression before occipital angles; in profile, outline of dorsal margin of occipital corners almost flat. 2. Propodeal spines shorter, length of spine about equal to distance between bases of spines, where distance between bases of spines is measured distal to basal curvature.

Keys including this Species

• Key to Malagasy Strumigenys

Distribution

Latitudinal Distribution Pattern

Latitudinal Range: -15.66667° to -15.66667°.

North Temperate	North Subtropical	Tropical	South Subtropical	South Temperate

• Source: AntMaps

Distribution based on Regional Taxon Lists

Malagasy Region: Madagascar (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. ‎

Castes

Images from AntWeb

Holotype of Strumigenys chilo. Worker. Specimen code casent0005509. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by MCZ, Cambridge, MA, USA.

Nomenclature

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

• chilo. Strumigenys chilo Fisher, in Bolton, 2000: 651, figs. 391, 415 (w.q.) MADAGASCAR.

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 3.2, HL 0.80, HW 0.61, CI 76, ML 0.45, MI 56, SL 0.56, SI 92, PW 0.33, AL 0.82. Characters of chilo-complex. Mandibles almost straight and at full closure parallel. Apical fork of mandible sub tended by a third, shorter spiniform tooth; the fork effectively 3-dentate; without intercalary teeth or denticles. Preapical teeth absent. Upper scrobe margin ends anterior of preocular groove; when viewed in profile, upper scrobe margin curves downwards at anterior margin of vertical preocular groove of side of head and forms a carina that almost meets preocular lamina; scrobe margin does not extend across dorsal apex of preocular groove so that the latter extends uninterrupted to the cephalic dorsum. Eye large, convex, and plainly visible in full-face view. Dorsum of head sharply depressed behind middorsum, forming a very shallow concave impression before occipital angles; in profile, outline of dorsal margin of occipital corners almost flat. Scape long and slender, approximately straight, the leading edge with a row of slender hairs which are slightly flattened or spoon-shaped apically. Cephalic dorsum with inconspicuous curved fine ground-pilosity; the upper scrobe margin without a row of hairs. Cephalic dorsum with 4 simple standing hairs arranged in a transverse row close to the occipital margin. Dorsum of head reticulate-punctate. Pronotum without standing hairs. Mesonotum with one pair of stout standing remiform to narrowly clavate hairs on anterior margin. Propodeum with one or two pairs of short, fine, posteriorly curved hairs immediately anterior of propodeal spines or on the basal third of the spines. Ground-pilosity on alitrunk as on head but sparser. With the alitrunk in profile the posterior portion of the mesonotum sharply depressed, the metanotal groove represented by a shallow impression. Pronotal humeri rounded to bluntly marginate. Lateral margin of posterior pronotum bluntly marginate. Anterior mesonotum without a narrow carina above the mesothoracic spiracle. Propodeal spines slender, almost spiniform; length of spines about equal to distance between base of spines, distance between base of spines measured distal to basal curvature; propodeal lamella absent. Alitrunk dorsum and sides reticulate-punctate. Petiole node in dorsal view reticulate-punctate and much longer than broad. Postpetiole disc reticulate-punctate. Spongiform appendages of petiole absent, extremely reduced on postpetiole but the latter with a spongiform collar. Basigastral costulae fine to superficial across base of gaster without a central clear area; gaster smooth and shiny where clean. Dorsal surfaces of petiole and postpetiole each with a pair posteriorly projecting stout hairs; gaster with stout standing hairs which are weakly swollen apically. Colour dull yellow to light brown.

Paratypes. TL 3.4-3.6, HL 0.85-0.90, HW 0.61-0.68, CI 71-77, ML 0.50-0.52, MI 58-60, SL 0.62-0.65, SI 94-103, PW 0.34-0.37, AL 0. 89-0.96 (4 measured). As holotype.

The non-paratypic material shows greater size variation than the type-series alone: HL 0.68-0.97, HW 0.50-0.72, CI 71-79, ML 0.40-0.55, MI 56-63, SL 0.47-0.67, SI 91-106 (12 measured), but otherwise matches all critical diagnostic characters.

Type Material

Holotype worker, Madagascar: 5.3 km. SSE Ambanizana, Andranobe, 15°40'S, 49°58'E, 425 m., 21.xi.1993, sifted litter (leaf mold, rotten wood), rainforest, #926 (23)-10 (B. L. Fisher) (Museum of Comparative Zoology).

Paratypes. 2 workers with same data as holotype but coded (27)-8, (11)-6; 2 workers and 1 queen (dealate) with same data as holotype but labeled 25.xi.1993, ex rotten log, rainforest, and coded #961 (The Natural History Museum, South African Museum).

References

• Fisher, B.L. 2000. The Malagasy fauna of Strumigenys. Pp. 612-696 in: Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028. (page 651, worker described)

References based on Global Ant Biodiversity Informatics

• Bolton, B. 2000. The Ant Tribe Dacetini. Memoirs of the American Entomological Institute 65
• Fisher B. L. 2003. Formicidae, ants. Pp. 811-819 in: Goodman, S. M.; Benstead, J. P. (eds.) 2003. The natural history of Madagascar. Chicago: University of Chicago Press, xxi + 1709 pp.