Threat Level: Medium

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.

Monomorium are most often confused with Solenopsis and Cardiocondyla. Monomorium and Solenopsis lack propodeal spines and are often lightly sculptured or smooth. Solenopsis papuana and its minute, small-eyed relatives are easy to mistake for Monomorium. However, the antennal club of Monomorium is three or more segments, and that of Solenopsis is two segments.

Cardiocondyla also has a three-segmented antennal club, but the presence of propodeal spines (occasionally very small) and a swollen postpetiole (in dorsal view) can help separate it from Monomorium.

The development of polymorphic workers, punctate sculpture restricted to the propodeum and mesopleuron, and transverse ridges running across the posterior margin of the head makes M. destructor unique among PIAkey Monomorium. The dark gaster contrasting with the rest of the body can also be used as a relatively reliable character for species recognition within PIAkey.

There are many species of Monomorium that have spread across the Pacific Islands that are not included in the current version of PIAkey, including M. latinode, M. sechellense and species belonging to the M. salomonis group. Images of all these species are available at Antweb. Recent taxonomic revisions of the Australian and Malagasy Monomorium are also available (Heterick 2001, 2006).

Waist with two segments (petiole & postpetiole)
Propodeal spines absent
Antennal club with three segments
Mesonotum and propodeum sculptured Pronotum smooth and shining
Gaster darker than rest of body
Worker caste polymorphic

Chart 1. Monomorium vs. Cardiocondyla and Solenopsis
Chart 2. M. destructor vs. other Monomorium species

	Monomorium	Cardiocondyla	Solenopsis
Head
Profile
Propodeal spines	absent	present	absent
Number of antennal club segments	three	three	two
	Monomorium	Cardiocondyla	Solenopsis

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	M. destructor	M. floricola	M. liliuokalanii	M. pharaonis
Head
Profile
Mesosoma sculpture	absent from propodeum	absent	absent	all
Pale portions of body	all except gaster	mesosoma & waist	absent	all
	M. destructor	M. floricola	M. liliuokalanii	M. pharaonis

• Antweb: specimen images, data & maps
  
  
• Global Invasive Species Database: information about ecology, distribution, impacts, management, references, links and contacts
  
  
• Bolton, B. (1995) A new general catalogue of the ants of the world. Harvard University Press, Cambridge, Massachusetts, 504 pp.
  
  
• Heterick, B. (2001) Revision of the Australian ants of the genus Monomorium (Hymenoptera: Formicidae)
  Invertebrate Taxonomy, 15, 353-459.
  
  
• Heterick, B. (2006) A revision of the Malagasy ants belonging to genus Monomorium Mayr, 1855 (Hymenoptera: Formicidae). Proceedings of the California Academy of Sciences, 57, 69-202.
  
  
• Wilson, E.O. & Taylor, R.W. (1967) The ants of Polynesia (Hymenoptera: Formicidae). Pacific Insects Monograph, 14, 1-109.