Iridomyrmex anceps group - PIAkey factsheet

Threat Level: Low

Iridomyrmex anceps and its close relatives are considered here to belong to a group of species collectively referred to as the Iridomyrmex anceps group. The taxonomy of the group is currently unstable, and it is recommended that specimens matching the descriptions given PIAkey be determined as "Iridomyrmex anceps group" until a detailed study of the species is completed.

Wilson and Taylor (1967) have the following to say about Iridomyrmex anceps Roger:

Anceps is the most widespread of the Indo-Australian Iridomyrmex, ranging continuously from India to eastern Australia, through micronesia and almost all of Melanesia. The above record [Cook Islands: Aitutaki] is the first from Polynesia. Evidently the species is in the process of spreading with the help pf man. We have recently seen the first series collected from Fiji...The great distance of the Cook Is. from the nearest source populations also indicates spread by commerce.

Although the species is widely introduced, it is not generally considered to be a pest species, and there is little known about its effects on native biological diversity, agriculture or human health.

In the Pacific Island region, I. anceps can be most easily confused with other Dolichoderine species from the genera Technomyrmex, Tapinoma and Linepithema. Users are referred to the comparison chart section for ways to distinguish I. anceps from similar appearing species.

Waist with one segment that is raised, not flat
Gaster not armed with sting or acidopore
Eyes, in full face view, do not break outline of head
Dorsal surface of mesosoma with long, thin erect hairs present
Anterior margin of clypeus with distinct central protrusion

Iridomyrmex anceps group vs. Linepithema humile, Technomyrmex species and Paratrechina species.

	I. anceps group	L. humile	Technomyrmex spp.	Paratrechina spp.
Head
Profile
Anterior margin of clypeus with distinct median projection	yes	no	no	no
Petiole	raised	raised	flat	raised
Dorsum of mesosoma with erect hairs	present	absent	present	present
Hairs long thick and produced in pairs	no	no	no	yes
Eyes break outline of head	no	no	no	yes OR no
	I. anceps group	L. humile	Technomyrmex spp.	Paratrechina spp.

Iridomyrmex anceps group CASENT0171061 (head)	Iridomyrmex anceps group at sugar solution bait (units in mm) Lautoka, Fiji
Iridomyrmex anceps group CASENT0171061 (profile)	Iridomyrmex anceps group at sugar solution bait Lautoka, Fiji
Iridomyrmex anceps group CASENT0171061 (dorsal)	Iridomyrmex anceps group at sugar solution bait Lautoka, Fiji
Iridomyrmex anceps group CASENT0171061 (label)

Iridomyrmex anceps group at cotton ball and sugar solution bait (Lautoka, Fiji).

Subfamily Dolichoderinae

Although many specimens have, in the past, been determined as I. anceps, it is not clear that these specimens match the type specimen from Malaysia designated by Roger (1863). Subspecies are described from Fiji (ignoblis), New Caledonia (neocaledonica, unavailable name), India (sikkimensis) and Burma (watsonii), but it is not clear if they are native to those regions or are geographic subpopulations I. anceps. A taxonomic revision of the group is required to determine if the specimens commonly identified as I. anceps represent one species or several species.

Iridomyrmex anceps. Formica anceps Roger, 1863a: 164 (w.) WEST MALAYSIA. Karavaiev, 1926d: 433 (m.); Imai, Baroni Urbani, et al. 1984: 8 (k.). Combination in Iridomyrmex: Dalla Torre, 1893: 168. Senior synonym of excisus: Dalla Torre, 1893: 168; Forel, 1895e: 469; Emery, 1895k: 475; of papuana (and its junior synonym discoidalis): Wilson and Taylor, 1967: 78. Material of the unavailable name neocaledonica referred here by Taylor, 1987a: 33. Current subspecies: nominal plus ignoblis, sikkimensis, watsonii.

Antweb: specimen images, data & maps
Bolton, B. (1995) A new general catalogue of the ants of the world. Harvard University Press, Cambridge, Massachusetts, 504 pp.
Wilson, E.O. & Taylor, R.W. (1967) The ants of Polynesia (Hymenoptera: Formicidae). Pacific Insects Monograph, 14, 1-109.