Nothing is known about the biology of Monomorium hirsutum.
Known only from the type-series, hirsutum has been treated to the present as a subspecies of Monomorium bicolor. It is, however, conspicuously densely hairy, in contrast to bicolor which lacks hairs on the dorsal alitrunk and has only sparse gastral pilosity. M. hirsutum also has shorter scapes and smaller eyes than bicolor, as follows.
M. bicolor SI 104-115, maximum diameter of eye 0.24-0.27 x HW
M. hirsutum SI 99-103, maximum diameter of eye 0.19-0.21 x HW
The closest relative of hirsutum appears to be an unidentified species from South Yemen (in BMNH) which matches hirsutum in colour, pilosity and general appearance, but which has erect pubescence on the scapes, even smaller eyes, and a deeply impressed metanotal groove followed by a conspicuously convex propodeal dorsal outline. In hirsutum the metanotal groove is very shallow and the propodeal dorsum is more or less flat in profile, approximately continuing the line of the promesonotum.
M. hirsutum is easily distinguished from all other Afrotropical members of the bicolor-complex as it is the only species to have hairs present on the propodeum. Only one other species in the entire salomonis-group, as represented in sub-Saharan Africa, has the propodeum densely hairy, Monomorium albopilosum, but this is quickly distinguished by the characters noted in the key.
Keys including this Species
Distribution based on Regional Taxon Lists
Distribution based on AntMaps
Distribution based on AntWeb specimens
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The following information is derived from Barry Bolton's New General Catalogue, a catalogue of the world's ants.
- hirsutum. Monomorium bicolor subsp. hirsutum Forel, 1910c: 251 (w.) ETHIOPIA. Subspecies of subopacum: Santschi, 1927d: 245. Raised to species: Bolton, 1987: 345.
Unless otherwise noted the text for the remainder of this section is reported from the publication that includes the original description.
Bolton (1987) - TL 3.2-3.4, HL 0.76-0.82, HW 0.62-0.67, CI 81-83, SL 0.62-0.68, SI 99-103, PW 0.40-0.44, AL 0.90-1.00 (6 measured).
Prominent median portion of clypeus with its anterior margin shallowly concave. Eyes smaller than in any other member of the bicolor-complex, the maximum diameter 0.19-0.21 x HW and with 9-10 ommatidia in the longest row. Petiole and postpetiole nodes about equal in width in dorsal view (ca 0.20-0.22), each distinctly transverse, anteroposteriorly compressed and broader than long. Propodeal dorsum slightly longitudinally impressed medially but lacking lateral carinae or marginations. Dorsum of head, entirety of alitrunk, petiole and postpetiole, all evenly densely reticulate-punctate, the punctures small, very crowded and all sharply defined. First gastral tergite shagreenate, the sculpture densest basally and fading apically. Dorsal surfaces of head, promesonotum, propodeum, petiole , postpetiole and gaster all with numerous fine standing hairs which are erect to subdecumbent and very dense; the propodeal dorsum with 5-6 pairs of hairs. Occipital margin of head in full-face view with projecting hairs across its entire width. Sides of head behind eyes with 1-2 pairs of projecting hairs in front of each occipital corner which are closer to the corner than to the eye. Head, alitrunk, petiole and postpetiole orange-yellow to orange-red, the gaster blackish brown to black.
- Bolton, B. 1987. A review of the Solenopsis genus-group and revision of Afrotropical Monomorium Mayr (Hymenoptera: Formicidae). Bulletin of the British Museum (Natural History). Entomology. 54: 263-452. PDF (page 345, Raised to species)
- Forel, A. 1910c. Ameisen aus der Kolonie Erythräa. Gesammelt von Prof. Dr. K. Escherich (nebst einigen in West-Abessinien von Herrn A. Ilg gesammelten Ameisen). Zool. Jahrb. Abt. Syst. Geogr. Biol. Tiere 29: 243-274 (page 251, worker described)
- Santschi, F. 1927e. Révision myrmécologique. Bull. Ann. Soc. Entomol. Belg. 67: 240-248 (page 245, Subspecies of subopacum)