Plagiolepis silpaarchai

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Plagiolepis silpaarchai
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Formicinae
Tribe: Plagiolepidini
Genus: Plagiolepis
Species: P. silpaarchai
Binomial name
Plagiolepis silpaarchai
Phosrithong & Jaitrong, 2024

Plagiolepis silpaarchai inhabits lowland (ca. 250 m a.s.l.) in northern Thailand and Laos. The type series was collected with a pitfall trap in a disturbed area near a mixed deciduous forest (Fig. 10) during the dry season.

Photo Gallery

  • Phosrithong et al. (2024), Figs 3–4. Plagiolepis workers, head in full-face view. 3 – P. chomphuphuangi (holotype, THNHM-I-00018330); 4 – P. silpaarchai (holotype, THNHM-I-27222).
  • Phosrithong et al. (2024), Figs 5–6. Plagiolepis workers, Mesosoma in dorsal view. 5 – P. chomphuphuangi (holotype, THNHM-I-00018330); 6 – P. silpaarchai (holotype, THNHM-I-27222).
  • Phosrithong et al. (2024), Figs 7–8. Plagiolepis silpaarchai, holotype worker (THNHM-I-27222). 8 – body in profile view; 9 – body in dorsal view.
  • Phosrithong et al. (2024), Figs 9–10. Type localities. 9 – Plagiolepis chomphuphuangi; 10 – Plagiolepis silpaarchai.


Plagiolepis silpaarchai can be easily distinguished from other congeners by the following characteristics:

  1. body large and dark brown
  2. dorsa of head and gastral tergites with dense erect setae
  3. dorsum of head finely and densely striate
  4. dorsum of mesosoma densely punctate
  5. setae on dorsa of pronotum and gastral tergites relatively long, usually longer than maximum width of antennal scape

Plagiolepis silpaarchai is similar to Plagiolepis rogeri and Plagiolepis jerdonii from India; Plagiolepis adynata and Plagiolepis demangei from Vietnam; and Plagiolepis nitida from Cambodia in having a dark body colour. However, Plagiolepis silpaarchai can be easily separated from them by the head being finely striated (in other species smooth and shiny). Plagiolepis silpaarchai is similar to P. demangei and P. jerdonii in having dense erect setae on the body dorsum. This species can be distinguished from P. demangei by 1) head slightly longer than broad (clearly shorter than broad in P. demangei); 2) head striate (smooth and shiny in P. demangei); 3) setae on pronotun clearly shorter than those on gastral tergite II (distinctly longer in P. demangei). Plagiolepis silpaarchai can be separated from P. jerdonii by the following characteristics: 1) head relatively shorter (CI 89-105 in new species; CI 88 in P. jerdonii); 2) mesothorax distinctly reduced, metanotum deep (mesothorax broad and metanotum shallow in P. jerdonii); 3) pronotum with erect setae (setae appressed in P. jerdonii).

Plagiolepis silpaarchai is also similar to Plagiolepis chomphuphuangi in having dense striation on dorsum of head. However, P. silpaarchai can be separated from P. chomphuphuangi by 1) dorsum of mesosoma entirely punctate (smooth and shiny in P. chomphuphuangi, see Figs. 5 and 6 for comparison); 2) setae on dorsa of pronotum and gastral tergites relatively long, usually longer than maximum width of antennal scape (usually shorter than maximum width of antennal scape); 3) pronotum and first gastral tergite with erect setae (suberect setae in P. chomphuphuangi, see Figs. 1 and 7 for comparison); 4) posterior margin of head almost straight or feebly concave (weakly convex in P. chomphuphuangi, see Figs. 3 and 4 for comparison).

Keys including this Species


  • Phosrithong et al. (2024), Fig 21. Distributions of the new species of Plagiolepis in Indochina.

Latitudinal Distribution Pattern

Latitudinal Range: 18° to 16.5°.

Tropical South
  • Source: Phosrithong et al., 2024

Distribution based on Regional Taxon Lists

Oriental Region: Laos, Thailand (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.




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

  • silpaarchai. Plagiolepis silpaarchai Phosrithong & Jaitrong, in Phosrithong et al., 2024: 7, figs. 4, 6-8 (w.) THAILAND.

Type Material

  • Holotype: worker (THNHM-I-27222, THNHM), Thailand: Kamphaeng Phet Province, Kosamphi Nakhon District, Ban Kosomphi, Khlong Wang Chao National Park, mixed deciduous forest, 16°30'16 N, 99°10'05 E, 18.XI.2021.
  • Paratypes: 16 workers (THNHM-I-27223 to THNHM-I-27238, THNHM), same data as holotype.