Royidris admixta

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Royidris admixta
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmicinae
Tribe: Crematogastrini
Genus: Royidris
Species group: admixta
Species: R. admixta
Binomial name
Royidris admixta
Bolton & Fisher, 2014

Royidris admixta casent0017121 p 1 high.jpg

Royidris admixta casent0017121 d 1 high.jpg

Specimen Labels

R. admixta has been retrieved from litter samples, pitfall traps, and rotten logs in spiny forest and in tropical dry forest.


A member of the admixta species group. Bolton and Fisher (2014) - This small species is most closely related to Royidris depilosa, but is easily separated from it by differences in sculpture and pilosity. In particular, admixta always has setae present at the pronotal humeri (absent in depilosa), and its head and promesonotal dorsum are entirely sculptured (mostly to entirely smooth in depilosa).

Keys including this Species


Endemic to Madagascar.

Distribution based on Regional Taxon Lists

Malagasy Region: Madagascar (type locality).

Distribution based on AntMaps


Distribution based on AntWeb specimens

Check data from AntWeb



Males have yet to be collected.




The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.

  • admixta. Royidris admixta Bolton & Fisher, 2014: 44, figs. 36-38, Map 134(w.q.) MADAGASCAR.

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



(holotype in parentheses). TL 1.8–2.3 (1.9), HL 0.46–0.56 (0.51), HW 0.36–0.47 (0.40), CI 78–83 (78), SL 0.34–0.44 (0.38), SI 92–95 (95), PW 0.26–0.34 (0.29), WL 0.54–0.68 (0.58) (12 measured).

Antennal club 3-segmented. Scapes short (SI < 100); when laid straight back in full-face view the apex of the scape just fails to reach the posterior margin of the head. With head in full-face view the eyes in front of the midlength of the side of the head capsule. EL 0.09–0.12 (EL/HW 0.24–0.27). Entire dorsum of head very finely reticulate-punctulate to reticulate-shagreenate. Promesonotum in profile not swollen or domed, the dorsum shallowly convex to the weakly impressed metanotal groove. Propodeal dorsum more or less flat and slopes posteriorly, the dorsal line of the propodeum approximately follows that of the promesonotum; the propodeum is not strongly depressed below the level of the promesonotum. Pronotum with a short seta at each humeral angle; sometimes a second pair is present on the pronotum behind the humeral pair. Mesonotum frequently with a single pair of short setae, but setae always absent from the propodeum. Dorsum of mesosoma finely reticulate-punctulate to reticulate-shagreenate everywhere; entire side of mesosoma finely reticulate-punctulate. Metafemur relatively short, MfL 0.34–0.44 (MfL/HW 0.90–0.97, MfL/MfH 2.85–3.36). Petiole with a single pair of setae on the posterior face of the node; postpetiole with 2–4 setae present posteriorly; first gastral tergite with setae present anterior to those at the extreme posterior margin. Postpetiole relatively broad in dorsal view, maximum width 0.16–0.20 (0.42–0.45 × HW). Colour dull yellow to yellowish brown; gaster may be somewhat darker.


(gyne). Alate when virgin. TL 3.9–4.1, HL 0.68–0.70, HW 0.61–0.62, CI 87–90, SL 0.54, SI 87–89, PW 0.51–0.54, WL 1.14–1.18 (2 measured). EL 0.18–0.20 (EL/HW 0.30–0.32). Sculpture of dorsum of head similar to worker, but with fine longitudinal striolate sculpture behind the frontal carinae, and with very weak, fine transverse striolae behind the ocelli. Mesoscutum unsculptured, maximum length 0.60–0.61, maximum width 0.51–0.54. Mesoscutum and scutellum with numerous erect, short setae, but setae absent from propodeum. Metafemur longer than in worker and slightly less incrassate, MfL 0.59–0.62 (MfL /HW0.96–1.00, MfL/MfH 3.93–4.23). Propodeum with a pair of short, broad, triangular teeth.

Type Material

Holotype worker, Madagascar: Prov. Toliara, P.N. Andohahela, 1.7 km. 61° ENE Tsimelahy, 300 m., 24°56’S, 46°39’E, 16–20.i.2002, BLF 4916 (49), CASENT0017121, sifted litter, tropical dry forest (Fisher et al.) (California Academy of Sciences). Paratypes. 5 workers with same data as holotype but BLF 4916 (29), CASENT0016609; BLF 4916 (31), CASENT0016615; BLF 4916 (40), CASENT0017134; BLF 4916 (46), CASENT0016647; BLF 4916 (46), CASENT0016652 (CASC, The Natural History Museum).


  • Bolton, B. & Fisher, B.L. 2014. The Madagascan endemic myrmicine ants related to Eutetramorium (Hymenoptera: Formicidae): taxonomy of the genera Eutetramorium Emery, Malagidris nom. n., Myrmisaraka gen. n., Royidris gen. n., and Vitsika gen. n. Zootaxa 3791:1–99. doi:10.11646/zootaxa.3791.1.1

References based on Global Ant Biodiversity Informatics

  • Bolton B., and B. L. Fisher. 2014. The Madagascan endemic myrmicine ants related to Eutetramorium (Hymenoptera: Formicidae): taxonomy of the genera Eutetramorium Emery, Malagidris nom. n., Myrmisaraka gen. n., Royidris gen. n., and Vitsika gen. n. Zootaxa 3791(1): 1-99.