Monomorium smithii Forel 1892
Synonyms (Valentine & Walker 1991 )
Monomorium (Notomyrmex) smithi (Forel)
Monomorium is a large genus with well over 300 species. Bolton (1987) observes that the main centres of speciation include Africa and Australia. Heterick (2001) recognises 59 endemic species in Australia.
M. smithii is endemic to this country. Venom analysis (see section on M. antarcticum) reveals a unique mixture of alkaloids, clearly separating this species from members of the antarcticum “complex” (Jones et al. 1990).
Distribution (see map)
M. smithii occurs on both main islands, Three Kings Is (Taylor 1962; Don 1994), and particularly on offshore islands in the north.
In the genus Monomorium, antennae of the workers are 10 to 12-segmented (most often 12), usually with a conspicuous club. The front margin of the clypeus has a single central elongate hair. Metanotal groove present, either deeply or feebly impressed. Petiole and, generally, the postpetiole have distinct rounded nodes.
Diagnostic features of the worker
Length 2.3-2.6 mm; antennae 12-segmented; mandibles 5-toothed; metanotal groove feebly impressed (cf. most antarcticum workers); smooth and shiny without spines on the propodeum (cf. Huberia species); colour generally brownish-yellow, including antennae and legs. Workers move slowly even in warm conditions. This feature and their small size enable this species to be distinguished from M. antarcticum in the field. In addition, its colour differentiates it from dark forms of antarcticum.
NB: This species is very poorly represented in collections, probably because most specimens have been lumped with M. antarcticum.
Little of its biology is known. Its morphological similarity to M. antarcticum would suggest it is probably a generalist. Small colonies have been found nesting under small stones in the open grassland adjacent to native forest (AWD pers. obs.). Workers have been collected from beneath a turf mat of browntop and sweet vernal in open grassland with sparsely spaced hard tussock, Festuca novae-zealandiae, in inland Canterbury (see further details next paragraph).
M. smithii workers were observed carrying off untreated ryegrass seed from a field trial at Broken River, near Porter’s Pass, inland Canterbury (early December, 1972). It was thought that this activity might have been a factor in the poor establishment of the seed in the trial (R.J.M. Hay pers. comm.).
W.W. Smith (1896) found the pseudococcid, Dysmicoccus formicicola (Maskell) [Smith knew it as Ripersia formicola Maskell] associated with M. smithii in Canterbury. He observed the guests being carried off by the workers when the stone covering a nest was raised.
This species is collected occasionally in litter samples (indicating that it also inhabits native forests) and in pitfall traps.
Impacts not known, but considered unlikely to be a pest.
Compiled by Warwick Don & Richard Harris