Strumigenys assamensis

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

Strumigenys assamensis casent0900133 p 1 high.jpg

Strumigenys assamensis casent0900133 d 1 high.jpg

Specimen Labels

Nothing is known about the biology of Strumigenys assamensis.

Photo Gallery

  • Tang & Guenard (2023), Fig. 5. New species records of Strumigenys in full-face, profile and dorsal views. A–C. Worker of S. assamensis from Vietnam (LSF1694). D–F. Worker of S. caninafrom Hainan, mainland China (HNA-00095). G–I. Worker of S. dohertyi from Hainan, mainland China (HNA-0067).

Identification

Tang & Guenard (2023) - A member of the Strumigenys leptothrix-group that is provisionally assigned to the elegantula complex. All the specimens we examined have fully closed mandibles. Placing specimens against backlight suggests the observation of a principal dental row of around 7 teeth, followed by a series of small teeth and denticles, terminating in a small apical tooth. Assignment of this species to the elegantula complex should be confirmed using specimens with open mandibles.

Bolton (2000) - This very distinctive species was fully characterized in the original description. It is easily separated from all other known members of the leptothrix-group by the following combination of characters in the worker.

  1. Standing hairs absent from all dorsal surfaces of head and alitrunk.
  2. With head in full-face view the dorsolateral margins without projecting hairs anywhere along the length.
  3. Leading edge of scape and dorsal (outer) surface of middle and hind tibiae with short appressed hairs only, without long outstanding simple hairs.
  4. Scape relatively very short, SI 57-60.
  5. Clypeus with a low narrow median longitudinal carina, strongest posteriorly and fading out just before the anterior margin.
  6. Lateral spongiform lobe of petiole large and blister-like, extending from posterior margin of node as far forward as the spiracle on the peduncle.
  7. Propodeum without spines or teeth, instead with only a broad translucent lamella that runs the depth of the declivity, becoming broader basally.
  8. Standing hairs on first gastral tergite confined to extreme base of the sclerite.

The habitus of assamensis makes the closest approach to the Malagasy hoplites-complex of any of the Oriental and Malesian species. However, the pronotum is marginate in assamensis and characters 1, 5, and 6 above are unique in this species, not applying to the Malagasy representatives of the group. Character 5 is unique in the whole group. Only Strumigenys euryale has a clypeal crest but it is very high, densely clothed with spatulate hairs, and confined to the anterior half of the sclerite. The dentition of assamensis is described in the introduction to the group.

Keys including this Species

Distribution

The record of S. assamensis in northern Vietnam extends its native range south-eastward. Its presence in the states Assam and Nagaland in India and northern Myanmar is likely (Tang & Guenard, 2023).

Latitudinal Distribution Pattern

Latitudinal Range: 25.3° to 20.7°.

   
North
Temperate 		North
Subtropical 		Tropical South
Subtropical 		South
Temperate

Distribution based on Regional Taxon Lists

Oriental Region: India (type locality), Vietnam.
Palaearctic Region: China.

Distribution based on AntMaps

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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.
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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.
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Biology

Explore-icon.png 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.

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Castes

  • Liu, C. et al. 2020. Ants of the Hengduan Mountains, Figure 100, Strumigenys assamensis.

Nomenclature

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

  • assamensis. Strumigenys assamensis De Andrade, in Baroni Urbani & De Andrade, 1994: 61, figs. 35, 36 (w.) INDIA. Combination in Smithistruma: Bolton, 1995b: 384; in Pyramica: Bolton, 1999: 1673; in Strumigenys: Baroni Urbani & De Andrade, 2007: 115. See also: Bolton, 2000: 430.

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 2.78, paratypes 2.75-2.77; HL holotype 0.65, paratypes 0.64-0.65; HW holotype 0.51, paratypes 0.50-0.51; SL holotype 0.30, paratypes 0.29-0.30; ML holotype and paratypes 0.12; AL holotype 0.76, paratypes 0.72-0.75; PW holotype 0.27, paratypes 0.26-0.27; petiolar node maximum length holotype 0.26, paratypes 0.25-0.26; petiolar node maximum width holotype 0.14, paratypes 0.14-0.15; postpetiole maximum length holotype 0.17, paratypes 0.16-0.18; postpetiole maximum width, holotype 0.20, paratypes 0.19-0.22; gaster maximum width, holotype 0.47, paratypes 0.45-0.47. CI, holotype 78.5, paratypes 78-79.7; SI holotype 59, paratypes 57-59; MI holotype 18.5, para types 18.5-18.7; SMI holotype 250, paratypes 241-250.

Head with the dorsum posteriomedially raised into a broad tumulus. Occipital lobes small and flattened. Eyes small and ventral to the scrobes. Clypeus in dorsal view with a median carina, its latera-posterior sides connected with a narrow preocular lamina. Sides of the clypeus convex and converging anteriorly. Anterior clypeal margin convex. Preocular lamina narrow. Scape slightly less than half the head length, narrow and with marginate external border. Antennae six-jointed.

Labrum bilobed, triangular and hidden by the mandibles at rest. Mandibles with a triangular basal tooth followed by three acuminate, long teeth and four denticles alternating in size; five smaller denticles on the apical part.

Trunk: anterior border of the pronotum slightly marginate, its sides strongly marginate and rounded. Pronotum flat and with a feebly median longitudinal carina. Promesonotal suture well visible laterally and terminally impressed towards the dorsum. Sides of mesonotum and propodeum dorsally marginate but without transversal crest or carina. Mesopleural presumed glandular area well developed and bearing a brush of long setae. Propodeal suture feebly impressed only on the lower pleural area. Propodeal teeth short and stout with a broad infradental lamella originating from their apex.

Spongiform process on the ventral side of the petiole well developed longitudinally and as high as the petiolar node. Sides of the petiole with a broad lamella directed ventrally. Posterior border of the petiole with a thin transversal lamella. Ventral spongiform process of the postpetiole broad and rounded. Postpetiole with a well developed lamella embracing its lateral and posterior sides. Petiolar node rounded, 2/3 longer than the postpetiole. Postpetiole 1/4 broader than the petiolar node, slightly convex and hexagonal in dorsal view.

Gaster oval, slightly broader than the postpetiole. Sting protruding. Anterior border of the gaster with a broad, transverse lamella in part covered by the postpetiolar lamella.

Sculpture: head irregularly striate and punctate on the lateral and anterior parts and on the posterior border of the clypeus. Cephalic tumulus only slightly reticulo-punctate. Clypeus, antennae, mandibles and legs punctate. Alitrunk and abdomen shining and feebly punctate.

Pilosity: dorsum of the head, clypeus, antennae and legs with sparse appressed short hairs, longer over the antennae, the sides of the mandibles, and legs, and denser over the funiculi and mandibular sides. Dorsum of the mandibles covered by thick, spatulate hairs (Fig. 36 A). Thorax and abdomen with rare, appressed hairs as long as those on the dorsum of the head. Dorsum of the postpetiole with a pair of subdecumbent hairs as long as those on the antennae. Erect, thick, truncate, slightly longer hairs over the dorsum of the gaster arranged as follows: a row of four on the anterior border of the first segment and on the posterior border of the third segment, two on the posterior border of the second segment, and four on the fourth gastral segment.

Colour: body reddish-brown, shining, lighter on the clypeus, the antennae and the legs. A dark brown rim marks the posterior border of the clypeus, the antennal scrobes, the ventral border of the mesopleura, the dorsal margin of the alitrunk and propodeal declivity, and the dorsal border of the pedicel. Postpetiole with a thick dark, lateral expansion appearing as a spine embedded in the lamelliform process. A similar but much less evident spiniform colour pattern on the posterior border of the petiole and on the anterior border of the postpetiole.

Bolton (2000) - TL 2.7-2.8, HL 0.64-0.65, HW 0.50-0.51, CI 78-79, ML 0.12, MI 18-19, SL 0.29-0.30, SI 57-60, PW 0.26-0.27, AL 0.72-0.76 (measurements after Baroni Urbani & De Andrade, 1994).

Type Material

Holotype worker and paratype workers, INDIA: Megalaya, Cherrapunjee, 1200 m., 16.v.1976 (Wittmer & Baroni Urbani) (Naturhistorisches Museum, Basel, The Natural History Museum) [examined].

Etymology

assamensis is a Latin neologism to indicate the provenance of this species from the Indian state of Megalaya, formerly considered part of Assam.

References

References based on Global Ant Biodiversity Informatics

  • Baroni Urbani C., and M. L. De Andrade. 1994. First description of fossil Dacetini ants with a critical analysis of the current classification of the tribe (Amber Collection Stuttgart: Hymenoptera, Formicidae. VI: Dacetini). Stuttgarter Beiträge zur Naturkunde. Serie B (Geologie und Paläontologie) 198: 1-65.
  • Fontanilla A. M., A. Nakamura, Z. Xu, M. Cao, R. L. Kitching, Y. Tang, and C. J. Burwell. 2019. Taxonomic and functional ant diversity along tropical, subtropical, and subalpine elevational transects in southwest China. Insects 10, 128; doi:10.3390/insects10050128
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