Strumigenys chroa

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

Known from a range of forest habitats, this is a widespread species in Madagascar. Specimens have been collected from litter samples, rotten logs, foraging on vegetation and in a rotten stick.

Identification

Bolton (2000) - A member of the chroa complex in the Strumigenys scotti-group. A widely distributed but easily recognized member of the chroa-complex, this species is recognized by its lamellate upper scrobe margin, absence of a pronotal humeral hair and marginate ventral spongiform tissue of petiole.

Keys including this Species

• Key to Malagasy Strumigenys

Distribution

Latitudinal Distribution Pattern

Latitudinal Range: -13.977° to -22.68333°.

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

Expand 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

Worker

Images from AntWeb

Paratype of Strumigenys chroa. Worker. Specimen code casent0005511. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by CAS, San Francisco, CA, USA.

Worker. Specimen code casent0436719. Photographer April Nobile, uploaded by California Academy of Sciences.	Owned by CAS, San Francisco, CA, USA.

Nomenclature

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

• chroa. Strumigenys chroa Fisher, in Bolton, 2000: 674, figs. 404, 420 (w.) 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 0.67, CI 84, ML 0.30, MI 38, SL 0.44, SI 66, PW 0.35, AL 0.81. Characters of chroa-complex. Mandibles almost straight and at full closure parallel except at base. Proximal preapical tooth on mandible confluent with lamella on inner margin that extends to base; in full-face view inner margin of lamella more or less straight. Upper scrobe margin a broad lamella, about as wide as scape. Eye small, with about 10 ommatidia in total. Hairs on leading edge of scape slender and filiform. Cephalic dorsum densely clothed with rows of curved narrow spatulate to spoon-shaped ground-pilosity, the upper scrobe margins fringed with a dense row of hairs which are the same shape and size as those on the dorsum. Cephalic dorsum with 6 simple standing hairs arranged in a transverse row of 4 close to the occipital margin and a more anteriorly situated pair. Pronotal humeral hair absent. Anterior margin of mesonotum with a pair of clavate to remiform hairs; posterior mesonotum with 2 additional pairs which are similar in shape to anterior pair but shorter. Ground-pilosity on alitrunk as on head. Dorsum of alitrunk in outline convex anteriorly and more or less flat posteriorly; posterior portion of mesonotum slightly depressed below the anterior margin of propodeum. Anterior mesonotum sharply marginate laterally, forming a convex lamellate extension above the mesothoracic spiracle. Propodeal tooth lam ell ate and confluent with the greatly expanded lamella for more than half its length. Alitrunk dorsum reticulate-punctate; pleurae mostly smooth and shiny, peripherally reticulate-punctate. Disc of postpetiole smooth and shiny, in dorsal view conspicuously broader than long. Ventral and lateral spongiform tissue of petiole and postpetiole greatly developed; ventral spongiform tissue of petiole marginate medially. Base of first gastral tergite with a continuous row of costulae. Dorsal surfaces of petiole, postpetiole and gaster with stout standing hairs which are thickened apically. Colour dull yellowish brown.

Paratypes. TL 3.1-3.3, HL 0.77-0.82, HW 0.68-0.70, CI 86-88, ML 0.29-0.31, MI 37-38, SL 0.41-0.46, SI 61-65, PW 0.33-0.37, AL 0.78-0.86 (3 measured). As holotype.

This material included workers from higher elevations that were larger than the type-series: HL 0.80-0.93, HW 0.64-0.77, CI 80-84, ML 0.31-0.36, MI 36-41, SL 0.43-0.52, SI 66-72 (11 measured).

Type Material

Holotype worker, Madagascar: Provo Toliara, southern Isoky-Vohimena Forest, 22°41'S, 44°50'E, 730 m., 21.i.1996 (S. Razajimandimby) (Museum of Comparative Zoology).

Paratypes. 1 worker with same data as holotype; 2 workers with same data but labeled sifted litter (leaf mold, rotten wood), dry forest and coded #1312 (9)-3, and (6)-4 (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 674, 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.
• Fisher, B. 2002. Ant diversity patterns along an elevational gradient in the Reserve Speciale de Manongarivo, Madagascar. in Gautier, L. and S.M. Goodman, editors, Inventaire Florestique et Faunistique de la Reserve Speciale de Manongarivo (NW Madagascar)