Monomorium westi

The species was discovered by Mr Christopher West of Oxford University whilst sampling the insect fauna of Acacia trees. The ants were collected from sheets spread around the bases of trees which had been sprayed with insecticide to bring down the insect fauna. As other members of the bicolor-complex are terrestrial rather than arboreal I suspect that the specimens of westi had walked onto the sheets after spraying was complete, and were killed by residual insecticide. (Bolton 1987)

Identification
Bolton (1987) - A member of the M. bicolor complex in the M. salomonis species group. A distinctive member of the complex, with strongly developed dense reticulate-punctate sculpture and conspicuously contrasting colour pattern, westi is diagnosed by its strongly concave anteromedian clypeal margin which is flanked by a pair of sharp, freely projecting teeth, a character not seen in any other species of the complex.

Apart from this westi has much smaller eyes than Monomorium personatum (0.31-0.33 x HW), lacks the reduced basal tooth and ammochaete hairs diagnostic of Monomorium rufulum, lacks the dense alitrunk pilosity seen in Monomorium hirsutum, and has the gaster much more densely hairy than in Monomorium bicolor itself.

Distribution based on Regional Taxon Lists
Afrotropical Region: Kenya.

Nomenclature

 *  westi. Monomorium westi Bolton, 1987: 363, figs. 37, 43 (w.) KENYA.

Worker
Holotype. TL 3.0, HL 0.78, HW 0.60, CI 77, SL 0.65, SI 108, PW 0.40, AL 0.90.

Fourth (basal) tooth of mandible about the same size as the third tooth, not reduced to a minute denticle. Prominent median portion of clypeus with its anterior free margin strongly concave, the concavity flanked on each side by a sharp projecting tooth. With the head in full-face view the eyes at the midlength of the sides, maximum diameter of eye 0.23 x HW, with 10 ommatidia in the longest row. Occipital margin of head weakly indented medially, the sides evenly but very shallowly convex, almost straight. Alitrunk in profile with metanotal groove only feebly indicated, not sharply impressed. Propodeal dorsum not sharply marginate laterally, the mid-dorsal longitudinal strip of the propodeum only very weakly indented. Petiolar peduncle with a small anteroventral lobe-like process. Height of petiole node from spiracle to summit greater than the length of the anterior peduncle from spiracle to anteriormost point of the ventral process. Petiole node bluntly conical in profile, distinctly higher than the postpetiole node. In dorsal view both nodes of approximately equal width. Dorsum of head with 1-2 pairs of hairs behind the level of the frontal lobes, without hairs projecting from the sides of the head or from the occipital margin. Ventral surface of head with numerous projecting fine curved hairs and with a very long anteriorly curved pair behind the buccal margin. Dorsal alitrunk without standing hairs. Petiole node with one pair, and postpetiole with 3 pairs of backward directed hairs. First gastral tergite with hairs more or less evenly distributed over the sclerite, with about 7-8 pairs in front of the apical transverse row. First gastral sternites densely hairy. Dorsum and sides of head and all surfaces of alitrunk finely and densely reticulate-punctate, the individual punctures small, densely crowded and sharply defined. Petiole and postpetiole similarly sculptured but the punctures less sharply defined. First gastral tergite finely shagreenate, the sculpture densest basally and becoming more feeble apically. Head, alitrunk, petiole, postpetiole and appendages orange to dull orange, the gaster blackish brown to black, the two colours strongly contrasting.

Paratypes. TL 3.0-3.2, HL 0.80-0.84, HW 0.60-0.65, CI 73-80, SL 0.64-0.68, SI 105-110, PW 0.40-0.43, AL 0.92-0.96 (6 measured). As holotype but maximum diameter of eye 0.22-0.25 x HW, with 9-10 ommatidia in the longest row. Dorsum of head at most with three pairs of standing hairs behind the level of the frontal lobes; postpetiole with 3-4 pairs of backward directed hairs.

Type Material
Holotype worker, Kenya: Kora, 8.xii.1983, sample AT1 Acacia tortius (C. West). Paratypes, 3 workers with same data as holotype; 2 workers with same data but 30.xii.1983, sample AT3 (BMNH; ; ).

References based on Global Ant Biodiversity Informatics

 * 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.