Strumigenys leptothrix

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Strumigenys leptothrix
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. leptothrix
Binomial name
Strumigenys leptothrix
Wheeler, W.M., 1929

Strumigenys leptothrix casent0280704 p 1 high.jpg

Strumigenys leptothrix casent0280704 d 1 high.jpg

Specimen Labels

A colony of this species was found in an oval cavity (1 x 1.5 cm) at a depth between 10 to 15 cm in soil near the root of a forest tree. It contained 82 workers, 64 larvae and a queen. (Ogata & Onoyama 1998)

Identification

Bolton (2000) - A member of the Strumigenys leptothrix-group. Within this group the seven species Strumigenys alecto, Strumigenys benten, Strumigenys elegantula, Strumigenys formosimonticola, Strumigenys jacobsoni, Strumigenys japonica and leptothrix have the propodeum armed with a pair of spines that are subtended by laminate lamellae rather than by narrow cuticular carinae. At the top of the declivity the lamella is fused with the ventral margin of the propodeal spine for a part of its length, but the apex of the spine is usually free. At the bottom of the declivity the lamella continues into rounded lamellate propodeal lobes that are obviously not elongate-triangular and acute.

Of these seven species only leptothrix has a series of straight simple hairs that project from the leading edge of the scape. With the head in profile only leptothrix and jacobsoni have numerous standing long hairs that arise all over the surface from the posterior margin of the clypeus to the occipital margin. At least the anterior half of the cephalic dorsum lacks such hairs in alecto, benten, elegantula, formosimonticola and japonica. Differences distinguishing leptothrix from jacobsoni are tabulated under the latter name.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Oriental Region: Taiwan (type locality).
Palaearctic Region: Japan.


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.

  • leptothrix. Strumigenys (Cephaloxys) leptothrix Wheeler, W.M. 1929g: 55, fig. 7 (w.) TAIWAN. Terayama & Kubota, 1989: 787 (q.). Combination in Smithistruma (Weberistruma): Brown, 1948e: 107; in Weberistruma: Brown, 1949d: 8; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 122. See also: Bolton, 2000: 435.

Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.

Description

Worker

Length nearly 3 mm.

Head 1 2/3 times as long as broad, at the clypeus only 3/5 as broad as its greatest posterior width, rounded behind, without posterior lobes, with only slightly concave but distinctly marginate occipital border. Eyes small, behind the middle and far down on the sides. Clypeus convex, nearly as long as broad, semicircular in front, its posterior border angular in the middle and concave on each side. Frontal carinae very short but continued back on each side of the head as a sharp margination bounding the antennal scrobe and joining the transverse occipital margination. Mandibles small, triangular, convex, nearly three times as long as broad, their apical borders with a series of nearly a dozen, slender crowded teeth, which grow gradually longer towards the base. Antennal scapes reaching to the posterior fifth of the head; funicular joints 2 and 3 subequal, longer than broad, together equal to the fourth, which is half as long as the terminal joint. Thorax long, with long, shallow mesoepinotal constriction, somewhat flattened above, high through the epinotum, very low through the pronotum. Seen from above the pronotum is regularly elongate-elliptical, longer and broader than the remainder of the thorax, with a distinct median carina. Promesonotal and mesoepinotal sutures represented by transverse impressions. Mesonotum and base of epinotum rectangular, parallel-sided, the former longer, the latter shorter than broad and both with a strong lateral margination which is continued back to the epinotal teeth. These are rather small, triangular, longer than broad at their bases and directed backward. Declivity of epinotum perpendicular, about as long as the base, marginate and furnished with a low spongiform lamella on each side. Petiole, with a low convex node, somewhat longer than broad and as long as the peduncle. Postpetiole broader than long, transversely elliptical. Both nodes are surrounded laterally and posteriorly with abundant spongiform material and the ventral surfaces of their segments have dependent spongiform masses fully as deep as the segments that bear them. Gaster elongate-elliptical, with straight; transverse anterior border. Legs rather long.

Shining; mandibles opaque, very finely and indistinctly striate; clypeus very finely longitudinally rugulose; head densely punctate, its surface uneven, with loose, interrupted and rather feeble longitudinal rugae. Sides of thorax very smooth and shining, dorsum of pronotum obscurely longitudinally striate; epinotum and petiole opaque and densely punctate; postpetiolar node shining, with several small longitudinal impressions. Gaster very smooth and shining; first segment with several short, coarse striae at the extreme base.

Hairs pale yellow, fine and conspicuously long, but not very abundant, erect both on the body and the extensor surfaces of the femora and tibiae. Hairs on the mandibles and clypeus very small and appressed, those on the latter squamiform.

Yellowish ferruginous; antennae, legs and gaster somewhat paler and more yellow; mandibles and border of clypeus brown.

Bolton (2000) - HL 0.72-0.78, HW 0.48-0.50, CI 64-67, ML 0.08-0.09, MI 11-12, SL 0.38-0.40, SI 79-80 (2 measured). Leading edge of scape with 2-4 anteriorly projecting straight suberect simple hairs that are about as long as the maximum width of the scape. Leading edge of scape also with a series of short fine apically-curved hairs. Dorsolateral margin of head in full-face view with numerous freely projecting long simple hairs. With head in profile the dorsum with numerous anteriorly sloping standing hairs that arise all over the surface from the posterior margin of the clypeus to the occipital margin. Dorsal surfaces of body with numerous simple standing hairs on all segments except propodeum. Femora and tibiae with freely projecting straight simple hairs that are erect to suberect. Pronotum bluntly and weakly marginate dorsolaterally, the margination not conspicuous in profile; in dorsal view the sides of the pronotum project laterally beyond the marginations. Pleurae and side of propodeum smooth and shining, without reticulate-punctate or rugulose sculpture. Propodeal teeth short and subtended by distinct lamellae. Petiole node in profile with a differentiated short anterior face and a long curved dorsum. Lateral spongiform lobe of petiole extends anteriorly to a point almost level with the anterior face of the node.

Type Material

A single specimen from Funkiko, Formosa.

Bolton (2000) - Holotype worker, TAIWAN: Funkiko (F. Silvestri) (Museum of Comparative Zoology) [examined].

References

  • Baroni Urbani, C. and 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. 1999. Ant genera of the tribe Dacetonini (Hymenoptera: Formicidae). J. Nat. Hist. 3 33: 1639-1689 (page 1673, combination in Pyramica)
  • Bolton, B. 2000. The ant tribe Dacetini. Memoirs of the American Entomological Institute. 65:1-1028. (page 435, redescription of worker)
  • Brown, W. L., Jr. 1948e. A preliminary generic revision of the higher Dacetini (Hymenoptera: Formicidae). Trans. Am. Entomol. Soc. 74: 101-129 (page 107, combination in Smithistruma (Weberistruma))
  • Brown, W. L., Jr. 1949f. Revision of the ant tribe Dacetini. I. Fauna of Japan, China and Taiwan. Mushi 20: 1-25 (page 8, redescription of holotype; combination in Weberistruma)
  • Morisita, M.; Kubota, M.; Onoyama, K.; Ogata, K.; Terayama, M.; Yamauchi, K.; Sonobe, R.; Yamane, 1992. A guide for the identification of Japanese ants. III. Myrmicinae and supplement to Leptanillinae. (Hymenoptera: Formicidae). Tokyo: Myrmecological Soc (page 70, see also)
  • Ogata, K. 1991b. A generic synopsis of the poneroid complex of the family Formicidae (Hymenoptera). Part II. Subfamily Myrmicinae. Bull. Inst. Trop. Agric. Kyushu Univ. 14: 61-149 (page 135, see also)
  • Ogata, K.; Onoyama, K. 1998. A revision of the ant genus Smithistruma Brown of Japan, with descriptions of four new species (Hymenoptera: Formicidae). Entomol. Sci. 1(2): 277-287 (page 282, see also)
  • Terayama, M.; Kubota, S. 1989. The ant tribe Dacetini (Hymenoptera, Formicidae) of Taiwan, with descriptions of three new species. Jpn. J. Entomol. 57: 778-792 (page 787, queen described, revived combination)
  • Terayama, M.; Lin, C.-C.; Wu, W.-J. 1996. The Taiwanese species of the ant genus Smithistruma (Hymenoptera, Formicidae). Jpn. J. Entomol. 64: 327-339 (page 336, see also)
  • Wheeler, W. M. 1929h. Ants collected by Professor F. Silvestri in Formosa, the Malay Peninsula and the Philippines. Boll. Lab. Zool. Gen. Agrar. R. Sc. Super. Agric. 24: 27-64 (page 55, fig. 7 worker described)