Monomorium nimihil

This species is only known from a single sample, procured from pitfall traps set up on a steep slope near a permanent brook, among well-developed leaf and humus layers under and around fig trees (most likely Ficus cordata var. salicifolia (Vahl) C.C. Berg). In the samples from these traps it was the most numerous ant: 13 of 34 specimens (Collingwood 2004). No new material was collected during the study by Sharaf et al. (2017).

Identification
Collingwood (2004) - The combination of sculptured mandibles, circular propodeal spiracle and round eyes near the midlength of head sides places Monomorium nimihil  in the Monomorium salomonis group sensu Bolton (1987). Almost unsculptured dorsal surfaces of head and alitrunk in conjunction with numerous long hairs in these areas are not found in any other African or Arabian representative of that species-group.

In body profile and with the abundant pilosity, M nimihil is quite like the southern African Monomorium albopilosum, - a member of the Monomorium opacum-complex of the M. salomonis-group. However, M. albopilosum is much larger (HL ~ 0.91 mm, HW ~ 0.68 mm) with comparatively smaller eyes (diameter at most 0.25 times the HW) and has — as all species in the M. opacum-complex — conspicuous reticulate-punctate sculpture on head and alitrunk. Only one other African species of the M salomonis-group, M. hirsutum, and one Arabian species, Monomorium yemene, are densely hairy. They belong to the Monomorium bicolor-complex and thus have a distinctly contrasting dark gaster, are even more strongly sculptured than M. albopilosum  and have even smaller eyes.

Sharaf et al. (2017) - Worker. Head nearly square with feebly convex sides and strongly concave posterior margin; eyes large with 10–11 ommatidia in the longest row; mandibles sculptured; body pilosity abundant. Body colour uniform yellow.

Distribution
Socotra Island, Yemen.

Distribution based on Regional Taxon Lists
Afrotropical Region: Socotra Archipelago, Yemen.

Nomenclature

 * . Monomorium nimihil Collingwood, in Collingwood, et al. 2004: 485, fig. 12 (w.) YEMEN (Socotra I.).
 * Type-material: holotype worker, 12 paratype workers.
 * Type-locality: holotype Yemen: Socotra I., Wadi Daneghan, 12°37’N, 54°04’E, 90 m., 28-30.x.2000, pitfall trap (A. van Harten & H. Pohl); paratypes with same data.
 * Type-depositories: HLMD (holotype); BMNH, HLMD, NHCY, WMLC (paratypes).
 * Status as species: Borowiec, L. 2014: 123; Sharaf, Fisher, et al. 2017: 29.
 * Distribution: Yemen.

Worker
AL 0.71 mm, HL 0.63 mm, HW 0.59 mm, SL 0.63 mm, CI 94, SI 106 (4 specimens measured).

Head almost square with mildly convex sides and slightly concave occiput. Many long hairs present over the whole body, slightly shorter on the ventral head. Scapes and legs thickly clothed with suberect pubescence. Eyes, placed medially, relatively large (diameter 0.30 times the HW) with 10-11 ommatidia in the longest row. Petiole and postpetiole nodes wider than long in dorsal view (PW = 0.30 x HW). Body colour entirely yellow, shining with very superficial sculpture on the head and propodeum.

Type Material
Holotype worker: Yemen, Socotra Island, Wadi Daneghan, l2°37'N 54°04'E, 90 m, pitfall trap, 28-30.X.2000, A. van Harten & H. Pohl, HLMD-Hym-2087-HT. — Paratypes: Yemen, Socotra Island: 3 workers same data as holotype, HLMD-Hym-2087-PT1 to -PT3 [HLMD-Hym-2087-PT3 preserved as SEM preparation]; 4 workers, same data as holotype, NHCY; 4 workers, same data as holotype, CCC; 1 worker: same data as holotype,.

Etymology
The specific name (a noun in apposition) is the term for “ant” in the Socotri language.

References based on Global Ant Biodiversity Informatics

 * Collingwood, C. A., H. Pohl, and R. Güsten. "The ants (Insecta: Hymenoptera: Formicidae) of the Socotra archipelago." Fauna of Saudi Arabia 20 (2004): 473-495.