Strumigenys nanzanensis

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Strumigenys nanzanensis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. nanzanensis
Binomial name
Strumigenys nanzanensis
Lin & Wu, W.-J., 1996

Strumigenys nanzanensis casent0280740 p 1 high.jpg

Strumigenys nanzanensis casent0280740 d 1 high.jpg

Specimen Labels

Collected from rainforest and rubber plantation litter-samples. It is a relatively rare species in Hong Kong known only from secondary forests at elevations between 143 and 230 m (Tang et al., 2019).

Identification

Bolton (2000) - A member of the godeffroyi complex in the Strumigenys godeffroyi-group. Thirteen species in the godeffroyi-complex have predominantly smooth pleurae and side of propodeum. Six of these, Strumigenys berkalial, Strumigenys chimaera, Strumigenys eumekes, Strumigenys minutula, nanzanensis and Strumigenys vassago, have the pair of erect hairs closest to the midline on the occipital margin long and fine and either abruptly angled anteriorly in their apical halves or with their apical halves looped (best seen with the head in profile). In the other seven species (see under godeffroyi) the hairs at this location are short and stiff, erect or nearly so, and straight or at most only very shallowly evenly curved.

Of the five species listed above chimaera has relatively long mandibles and scapes, MI 56-58, SI 105-107, as opposed to MI 35-44, SI 74-100 in the other four species combined. Also in chimaera the mandibles in full-face view slightly increase in width from the base to a point at about two-thirds their length, and the inner margin is more or less straight through this length. In the distal third or so the inner margins of the blade shallowly angle outwards so that the mandible decreases in width to the preapical tooth and beyond. In the other five species (berkalial, eumekes, minutula, nanzanensis, vassago) the mandibles lack this shape and change of direction of the inner margin; the latter is usually evenly shallowly concave from base to preapical tooth.

S. eumekes stands apart from the others as it possesses a pair of extremely long erect flagellate hairs on the cephalic dorsum that are located just anterior to the highest point of the vertex, close to the dorsolateral margin on each side. In addition the pronotum is entirely smooth and the flagellate apicoscrobal and pronotal humeral hairs are extremely long, about 0.87 X SL.

S. nanzanensis is larger (HL 0.58-0.71, HW 0.38-0.48, SL 0.34-0.42) than minutula, vassago and berkalial (combined ranges: HL 0.48-0.54, HW 0.34-0.39, SL 0.26-0.32). In nanzanensis and vassago the dorsum of the petiole node is reticulate-punctate whilst in minutula and berkalial it is smooth or very nearly so. Of the former pair the larger nanzanensis has dense conspicuous ground-pilosity on the pronotum and the dorsal surface of the propodeal tooth is surmounted by a convex longitudinal crest of spongiform tissue; it also has longer scapes (SI 85-93). The smaller vassago has sparse, dilute pronotal ground-pilosity and lacks a spongiform crest on the dorsum of the propodeal tooth; its scapes are shorter (SI 74-81).

Of the final pair berkalial has relatively longer mandibles and scapes (MI 41-42, SI 91); it has small eyes with only 4-5 ommatidia in total, has longitudinal costulate-rugulose sculpture on the pronotal dorsum, lacks a convex longitudinal crest of spongiform tissue on the dorsum of the propodeal tooth, and in dorsal view the petiole node has a truncated transverse anterior face. In contrast minutula has shorter mandibles and scapes (MI 35-38, SI 74-77); it has larger eyes with more than 5 ommatidia, has only reticulate-punctate sculpture on the pronotal dorsum, has a convex longitudinal crest of spongiform tissue on the dorsum of the propodeal tooth, and in dorsal view the sides of the petiole node converge to an anteromedian point.

Keys including this Species

Distribution

Distribution based on Regional Taxon Lists

Indo-Australian Region: Indonesia, Malaysia.
Oriental Region: Bhutan, India, Taiwan (type locality), Thailand.
Palaearctic Region: China.

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.

  • nanzanensis. Strumigenys nanzanensis Lin & Wu, 1996: 148, figs. 13, 30-34 (w.q.) TAIWAN. See also: Bolton, 2000: 795.

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

Description

Worker

Bolton (2000) - TL 2.2-2.6, HL 0.58-0.71, HW 0.38-0.48, CI 66-71, ML 0.24-0.29, MI 40-47, SL 0.34-0.42, SI 85-93, PW 0.24-0.30, AL 0.58-0.70 (17 measured).

Characters of godeffroyi-complex. Cephalic dorsum with pair of erect hairs closest to midline on occipital margin fine, basal portion of hair erect and apical third or more abruptly angled or hooked anteriorly, or looped. With head in full-face view the dorsolateral margin posterior to the flagellate apicoscrobal hair has a row of 3-4 stiffly projecting hairs. These hairs contrast with the marginal hairs anterior to the flagellate hair as they are more cylindrical (i. e. not spatulate), more elevated and less strongly curved anteriorly. Ground-pilosity on pronotal dorsum dense and conspicuous, curved linear-spatulate and somewhat elevated. Dorsum of pronotum reticulate-punctate and with a pair of erect flagellate hairs in addition to the humeral pair. Mesonotum posteriorly with ground-pilosity that is long, narrowly spatulate, strongly elevated and curved. Pleurae and side of propodeum mostly to entirely smooth, any reticulate-punctate sculpture present is confined to periphery. Propodeal declivity with a broad and very conspicuous spongiform lamella, the propodeal teeth only weakly expressed (may be vestigial) and entirely buried in the lamella. Dorsal surface of propodeal tooth in profile surmounted by a convex crest or ridge of spongiform tissue. Disc of postpetiole unsculptured. Basigastral costulae conspicuous but not extending half the length of the tergite.

Type Material

Bolton (2000) - Holotype worker, para type workers and queens, TAIWAN: Pintung Hsien, Nanzansban, 17.xii.1992 (C.-C. Lin) (National Taiwan University, Taiwan Agricultural Research Institute) [examined].

Etymology

Named after Nanzanshan, the type locality.

Determination Clarification

Bolton (2000) - This species was misidentified as godeffroyi in Bolton, 1998b: 92.

References