Paratrechina bourbonica (Forel, 1886)

Diagnosis of worker among Antkey species. Worker caste monomorphic. Antenna 12-segmented. Antennal club indistinct. Antennal scape length less than 1.5x head length. Eyes medium to large (greater than 6 facets); do not break outline of head. Dorsum of mesosoma with weakly impressed metanotal groove, but never with a deep and broad concavity; dull with dense overlapping pubescence. Propodeum and petiolar node both lacking a pair of short teeth. Propodeum lacking posteriorly projecting protrusion. Mesopleuron shiny, not dulled by dense pubescence (less than 25 hairs). Metapleuron with a distinct gland orifice. Middle and hind coxae same color as mesosoma, not a strongly contrasting pale white. Waist 1-segmented (may be hidden by gaster). Petiole upright and not appearing flattened. Gaster armed with acidopore. Distinct constriction not visible between abdominal segments 3+4. Gaster (especially first segment) with dense pilosity, giving it a dull appearance. Hairs long thick and produced in pairs. Pubescence uniformly dense across mesosoma. Macrosetae on mesosoma of moderate length, thick and stout, weakly tapering to a blunt tip. Body color dull brown to black.

Among other introduced and commonly intercepted Nylanderia species, N. bourbonica can be distinguished from N. flavipes, N. guatemalensis, N. vaga and N. vividula by the dense amount of pubescence on the dorsal surfaces of the promesonotum, mesopleuron and first gastral segment. Of the two remaining species (N. fulva and N. steinhelli) that have similarly dense pubescence in these regions, N. bourbonica is distinguished from the former by the darker brown to black color and the macrosetae which are moderate and blunt (versus long and flexuous). Nylanderia bourbonica is easily distinguished from N. steinhelli by the color of the coxae which are uniform with the rest of the legs and body (versus strongly contrasting white), and by the mesosomal pubescence which is uniformly dense across mesosoma (versus uneven, becoming denser on dorsum, more sparse laterally on pronotum and mesopleuron).