Monomorium destructor, commonly known as the Singapore ant, is considered here to be a significant threat to native biological diversity and human health. For a more complete review of the biology, impacts and management of M. destructor, users are referred to the IUCN/SSC Invasive Species Specialist Group (ISSG) web page. The species is believed to have originated in Africa, but now occurs in tropical regions across the globe, and is especially prevalent among the Pacific islands.
Diagnosis of worker among Antkey species. Worker caste polymorphic. Head shape ovoid. Antenna 12-segmented. Antennal club 3-segmented. Antennal scrobe lacking. Antennal insertions at least partly covered by frontal lobes; not surrounded by a raised sharp-edged ridge. Frontal lobes do not obscure face outline between mandible and eye Antennal scapes not conspicuously short; easily extended beyond eye level. Posterolateral corners of head unarmed, without spines. Eyes medium to large (greater than 6 facets); distinctly less than half head length. Mandibles triangular. Mesosoma with sculpture on mesonotum and propodeum, but pronotum smooth and shining. Mesosoma with erect hairs; punctate sculpture covering mesonotum and propodeum. Pronotal spines absent. Propodeum lacking spines or teeth. Waist 2-segmented. Petiole with peduncle; lacking large subpetiolar process. Postpetiole not swollen, in dorsal view not distinctly broader than long or distinctly wider than petiole. Color yellowish to brownish red with contrasting dark brown to black gaster.
Among introduced and commonly intercepted Monomorium, M. destructor is the only polymorphic species. It can also be distinguished from these congeners by the following characters: 1) gaster dark brown to black and contrasting with the yellowish to reddish head, body and waist; 2) erect hairs present on the mesosoma; 3) mesosoma with only the mesopleuron and parts of metapleuron are sculptured. Additionally, M. destructor tends to have transverse striations or carinulae on the posterodorsal portion of the head which are best seen in dorsal view.