Amblyopone australis Erichson 1842

Compiled by Warwick Don & Richard Harris

Biostatus: Introduced

Classification

Family:	Formicidae
Subfamily:	Amblyoponinae
Tribe:	Amblyoponini
Genus:	Amblyopone
Species:	australis

Common name(s)

Southern Michelin ant

Synonyms (WWW5; Valentine & Walker 1991 )

Amblyopone cephalotes Smith, Amblyopone australis var. fortis Forel, Amblyopone australis subsp. foveolata Wheeler, Amblyopone laevidens Emery, Amblyopone minor Forel, Amblyopone nana Emery, Amblyopone obscura Smith, Amblyopone cephalotes var. maculata Stitz, Amblypone australis var. cephalotes (Smith)

Origin

A. australis is probably a 19th century introduction from Australia. Brown (1958a) suspects its introduction by human agency (e.g., soil ballast in ships) during the early days of European settlement. The first record of A. australis in this country is from Drury, near Auckland in 1876. Brown (1958a), after examining specimens from Australia, New Guinea, New Hebrides and neighbouring islands, was unable to designate the New Zealand population a separate species and concluded that samples from Queensland most closely resembled the New Zealand population. However, Taylor (1978) maintains the taxonomic situation is not so clear-cut and provides evidence for a complex of similar species.

Distribution

In New Zealand, A. australis appears to be currently confined to the North Island and its offshore islands, including the Three Kings Is.

General Description

Identification

The genus Amblyopone has long slender mandibles with teeth along the inner margins. They are “fat waisted” with the petiole broadly attached posteriorly to the gaster. A. australis is the largest introduced ant established in New Zealand.

Diagnostic features of the worker

Outstretched length 4.5-8 mm; antennae 12-segmented; mandibles long and slender with 5 or 6 large teeth and sometimes 1 or 2 additional teeth nearer the base; clypeus with a row of about 12 minute denticles; petiole and hind tibiae as in A. saundersi; colour ranging from light yellow to black.

[Amblyopone australis] head. Image: April Nobile (Specimen code: CASENT0104578). www.antweb.org Image — Amblyopone australis head. Image: April Nobile (Specimen code: CASENT0104578). www.antweb.org

Amblyopone australis profile view. Image: April Nobile (Specimen code: CASENT0104578). www.antweb.org

[Amblyopone australis] dorsal view. Image: April Nobile (Specimen code: CASENT0104578). www.antweb.org Image — Amblyopone australis dorsal view. Image: April Nobile (Specimen code: CASENT0104578). www.antweb.org

Biology

Colony founding and other aspects of behaviour have been studied by Haskins and Haskins (1951), by means of field observations and artificial nests. A. australis is less subterranean than some Amblyopone species, sometimes foraging above ground on dark days. Workers are often sampled in pitfall traps (RJH pers. obs.). Normally colonies are limited in size (tens or hundreds), but occasionally can number around 2000 (Haskins & Haskins 1951). Typically nests are found under stones or logs and, when disturbed, workers will move down to the lower reaches of the nest.

As with A. saundersi, trophallaxis appears to be absent. The larvae are fed entirely on the partially dismembered bodies of insects and other arthropods, normally captured underground and paralysed or killed with the sting (Haskins & Haskins 1951). The larvae are highly active and frequently cannibalize one another if other food is short. Under similar circumstances, eggs (called trophic eggs) may serve as a food source both for the first brood larvae and for the queen herself. Queens forage for food for the first batch of larvae as in the primitive manner, and they maintain this behaviour in company with the workers well beyond the first generation of larvae. Pupal cocoons tend to be orange in colour.

Females emerge from nests some time after the males and, unlike the latter, do not fly immediately (Haskins & Haskins 1951). Instead, they run about with buzzing wings for quite a while before gradually and hesitatingly taking flight. Flights are of short duration. After alighting on shrubbery, the females become quiet, raising and folding the wings and extending and arching the gaster and rubbing it with the hind legs, probably to release a pheromone attractive to the males. Following fertilization the females typically re-enter the soil and each constructs an earthen cell in which she lays her first batch of eggs. Sometimes two or more nest-founding females may join forces to produce a polygynous nest.

Found in a variety of habitats from vegetated gardens, coastal scrub through to deep forest.

Pest Status

Role in native systems unknown. Queens occasionally fly into houses. Capable of stinging, but rarely encountered and not aggressive.