Strumigenys nepalensis

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Strumigenys nepalensis
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Attini
Genus: Strumigenys
Species: S. nepalensis
Binomial name
Strumigenys nepalensis
De Andrade, 1994

Pyramica nepalensis casent0102623 profile 1.jpg

Pyramica nepalensis casent0102623 dorsal 1.jpg

Specimen labels

Known from a number of rainforest habitats, all recorded collection data for this species are from litter samples. In Hong Kong it is a common species in urban forest patches or disturbed grassland (e.g. Mai Po Nature Reserve), with only a few records collected within secondary forests and one record within Feng Shui woods. Elevation records ranged from 1 to 135 m, suggesting that this species might prefer lowland habitats. The association of this species with relatively disturbed habitats suggests a potential tramp species, although other biological characteristics (e.g. polygyny, unicoloniality) are unknown at present (Tang et al., 2019).

Identification

Bolton (2000) - A member of the Strumigenys rostrata-group. Recognition of nepalensis is easy as it is the only species with 4-segmented antennae currently known from the regions under discussion. Its only known close relative in these regions is Strumigenys atropos; details of their differentiation are given under the latter name. The species is widely distributed but apparently relatively uncommon.

Keys including this Species

Distribution

Records of Strumigenys nepalensis in Hong Kong expand the current known native range of this species by 800 km eastward from Vietnam. A record from Mauritius (Casent0799280, Ile Aux Aigrettes, −20.419017, 57.730183, 5 m a.s.l., A. Suarez 2.VI.2005; Doug Booher pers. comm.) confirms the tramp character of this species. Specimens collected from Hong Kong, Macau and Mauritius are considered introduced (Tang et al., 2019).

Distribution based on Regional Taxon Lists

Indo-Australian Region: Malaysia, Singapore.
Oriental Region: India, Nepal (type locality), Thailand, Vietnam.
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.

  • nepalensis. Strumigenys nepalensis De Andrade, in Baroni Urbani & De Andrade, 1994: 57, figs. 33, 34 (w.q.) NEPAL. Combination in Smithistruma: Bolton, 1995b: 385; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 124. See also: Bolton, 2000: 460.

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

Description

Worker

TL, holotype 1.49, paratypes 1.44-1.49; HL holotype 0.39, paratypes 0.39-0.40; HW holotype 0.29, paratypes 0.29-0.30; eye maximum diameter holotype and paratypes 0.03; SL holotype 0.18, paratypes 0.17-0.19; ML holotype 0.09, paratypes 0.08-0.09; AL holotype 0.41, paratypes 0.39-0.42; PW holotype 0.19, paratypes 0.19-0.20; petiolar node maximum length holotype 0.10, paratypes 0.09-0.10; maximum width of the petiole holotype and paratypes 0.10; postpetiolar node maximum length holotype 0.13, paratypes 0.12-0.13; maximum width of the postpetiole holotype 0.17, paratypes 0.17-0.18; gaster maximum width holotype 0.27, paratypes 0.25-0.28. CI holotype 74, paratypes 74-77; SI holotype 62, paratypes 57-62; MI holotype 23, paratypes 20-23; SMI holotype 200, paratypes 200-237.

Head strongly converging anteriorly and with rounded occipital corners. Dorsal border of the antennal scrobes laminar. Eyes small, ventral to the antennal scrobes. Preocular lamina narrow and straight. Clypeus as broad as long. Anterior clypeal margin transverse, its median portion with a small prominence. Scapes slightly less than ½ of the head length, moderately broadened, flat and sharply bent at the base. Antennae with four antennomeres, the last joint longer than the rest of the funiculus. Labrum elongate, broad and rounded, longer than half of the masticatory margin. Mandibles short, less than 1/4 of the head length, slightly narrow and triangular; base of the masticatory border with a short diastema (partly covered by the clypeus when the mandibles are closed) and a stout and blunt tooth. True masticatory margin with a row of 5 teeth of which the third is the longest one, followed by two smaller teeth and a denticulate space before the pointed apex.

Trunk: dorsum with a faint median longitudinal carina bifurcating posteriorly on the anterior part of the propodeum. Promesonotal suture visible in dorsal view. Mesonotum in side view slightly convex. Lateral sides of mesonotum and propodeal dorsum marginate. Propodeum in profile angled at about 100°. Propodeal teeth triangular, acute and with broad infradental lamella.

Spongiform processes well developed on the pedicel, more projecting ventrally than laterally; the lateral projections connected each other by a thin dorsal lamina on the posterior articulation of the nodes. Ventral side of the petiole with a broad spongiform lamina narrower under the node. Petiolar lateral spongiform processes widening caudally. Posterolateral processes of the postpetiole reaching the gaster caudally.

Petiolar node slightly truncate anteriorly, ca. 1/3 shorter than the postpetiole. Postpetiole more than half wider than the petiole.

Gaster oval with protruding sting.

Sculpture: clypeus, cephalic dorsum, dorsum of the alitrunk and petiole reticulo-punctate. Scapes and legs simply punctate. Mandibles and dorsum of the postpetiole finely punctate and shining. Pleurae smooth and shining except some punctures on the anterior portion of the propleurae and on the dorsal border of the pleurae. Propodeal declivity smooth. Base of the first gastral tergite costulated, the remaining portion of the gaster smooth and shining.

Colour: generally brownish, slightly lighter on the trunk and appendages.

Pilosity: cephalic dorsum with short, subdecumbent, clavate hairs directed anteriorly. The same type of hairs but shorter on most of the clypeus. Rare, suberect, slightly clavate hairs twice as long than the preceding ones on posterior part of the vertex. Lateral sides of the head, external border of the scape, lateral and anterior sides of the clypeus with decumbent spatulate hairs, slightly longer than those on the dorsum of the head. Mandibles and funiculi with short, appressed, pointed hairs. Dorsum of alitrunk with 5 pairs of long, erect setae; two similar pairs on the petiole, and another two on the postpetiole; similar setae irregularly sparse over the gaster. Rare, appressed clavate hairs on the dorsum of the alitrunk and petiole. Legs covered with ticker, appressed, pointed hairs.

Queen

TL 1.71-1.74; HL 0.42; HW 0.32; eye maximum diameter 0.06; SL 0.18-0.19; ML 0.09; AL 0.47; PW 0.23-0.24; petiolar node maximum length 0.07-0.10; petiolar node maximum width 0.12; postpetiolar node maximum length 0.13-0.15; postpetiolar node maximum width 0.18-0.20; gaster maximum width 0.35-0.39. CI 76; SI 56-59; MI 21; SMI 200-211.

Except for the usual differences due to caste determination, very similar to the worker from which it differs essentially in the following characters:

Trunk: with the propodeal suture impressed. Posterior portion of mesonotal disc and scutellum flat.

Petiole truncate anteriorly and slightly concave, its node almost two times broader than long.

Pilosity: dorsum of alitrunk with 7-8 pairs of long, erect setae similar to those of the worker.

Type Material

Holotype: worker, 6 km NW of Narainghat, 250m, Nepal. Natural History Museum Basel Nepal Expedition, 1976, in the collection of the Natural History Museum, Basel, Switzerland.

Paratypes: ten workers and four dealate gynes, same data as the holotype; three workers from 5 km E of Manhari, 350m, Nepal. Natural History Museum Basel Nepal Expedition, 1976; one worker from Darugiri, 450 m, Garo Hills, (Megalaya, India), Natural History Museum Basel Megalaya Expedition, 1976. Most paratypes in the Natural History Museum, Basel; some paratypes deposited in the Natural History Museum, London.

Bolton (2000) - Holotype worker, paratype workers and queens, NEPAL: 6 km. NW of Narainghat, 30.v.1976, 250 m. (W. Wittmer & C. Baroni Urbani); paratype workers, NEPAL: 5 km. E of Manhari, 2.vi.1976 (W. Wittmer & C. Baroni Urbani), INDIA: Megalaya, Darugiri, Garo Hills, 450 m., 1976 (Naturhistorisches Museum, Basel, The Natural History Museum) [examined].

Etymology

nepalensis is a Latin neologism indicating the provenance from Nepal.

References