Amblyopone saundersi Forel 1892
New Zealand Michelin ant
Synonyms (Valentine & Walker 1991 )
Stigmatomma saundersii (Forel), Stigmatomma (Fulakora) saundersi (Forel)
According to Shattuck (1999) the genus Amblyopone contains 62 described species, 17 of which are known from Australia. A. saundersi is probably endemic to this country; it appears to be distinct from its relatives in Australia, suggesting a long period of isolation from an ancestral Australian form. It is a southern representative of a now discontinuous archaic group. Brown (1960) concludes that amblyopones have been able to survive in a world dominated by more advanced ant species through ecological specialisation (see below).
Distribution (see map)
This species is to be found predominantly in native forests on both main islands, Stewart I., offshore islands, Three Kings Is and Chatham Is. This wide distribution lends support to its probable endemicity.
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. saundersi is the smaller of the two species of this genus in New Zealand. Colonies rarely encountered and foragers not seen above ground in daylight.
Diagnostic features of the worker
Outstretched length 3-5 mm; antennae short, 12-segmented; mandibles long and slender, usually with 8 teeth, with a pointed tooth at their tips; clypeal teeth variable in number, 6-10; the petiole (anterior node) has distinct anterior and dorsal faces, but no posterior face, i.e. the petiole is attached broadly to the postpetiole, which in turn is attached broadly to the gaster; each tibia of the hind legs has a large, comb-like spur at its tip; colour varies from light yellow to dark brown.
Sluggish in movement and able to feign death, workers of this species occupy the cryptobiotic niche, nesting and foraging predominantly beneath leaf litter, stones and rotting logs. The short antennae and narrow body are clearly adaptations for a cryptobiotic way of life. Nests are extremely simple — merely a shallow hollow in the soil — and the colonies small,comprising only 10-30 workers (a primitive feature). Each nest in an area forms part of a diffuse colony of what is essentially a nomadic species; hence the simplicity and essentially temporary nature of the nests.
An effective sting is used to immobilise prey (chilopods, beetle larvae and other small arthropods), the worker seizing its victim in formidable mandibles and injecting a potent toxin. The toothed clypeus and labrum ensure a firm grip on struggling prey. Queens forage for food for the first batch of emerging workers, another primitive feature. Larvae are provided with pieces of prey, a procedure superseded in more advanced species by trophallaxis or the provision of regurgitated food. Each last instar larva spins a distinctive yellow cocoon in which it pupates.
Commonly sampled in pitfall traps and litter extractions in forest and scrub (including gorse scrub).
Queens occasionally fly into houses. Capable of stinging but rarely encountered.
Compiled by Warwick Don & Richard Harris