Divaricating shrubs are a dominant feature of the eastern and central South Island montane valley floors and slopes.
Among the bewildering array of these shrubs, the mainly deciduous, small-leaved daisy shrubs in the genus Olearia are conspicuous with their light green foliage and profuse fragrant flowers. There are at least 13 species of Olearia in this distinctive group.
Studies over the past decade have revealed a rich endemic moth fauna that depends on this suite of shrubs. A total of 41 moth species were found as larvae (caterpillars) feeding on different parts of the plants, from the flowers to fresh foliage, old foliage, buds and leaf litter.
At least three of these moths have tiny larvae mining within the thin leaves. Of the total, 17 species are Olearia specialists. By rearing larvae found on the shrubs, an amazing eight new species in five moth families were discovered.
With other insect orders such as beetles and bugs also richly represented, four species stand out for their importance to local invertebrate communities: Olearia odorata, O. fimbriata and O. hectorii of the South Island and O. gardneri of the North Island.
Several Olearia moths are now rare and threatened with extinction because of loss of or degradation of their habitat.
Among these are unnamed species in the genera Protosynaema, Pyrgotis and Pseudocoremia while Stathmopoda campylocha, Graphania tetrachroa, Meterana grandiosa and M. exquisita are also disappearing.
Above: This large new species in the genus Pseudocoremia is unusual as the female (pictured) is completely flightless with wings just 1mm long on a 1cm body.
Being effectively immobile, the species is dependent on a canopy of the host plant Olearia odorata to enable the female to walk from plant to plant amongst the foliage.
Dense shrublands of these plants are now rare, with scattered shrubs the normal situation, probably accounting for the demise of this and other Olearia dependent moths.
Above: Pseudocoremia larvae on Olearia odorata
Right: The well-camouflaged geometrid larvae (commonly called inchworms or loopers) of Pasiphila cotinaea feed on the flowers of various small-leaved Olearia shrubs.
The delicate green adults are found in many places in the South Island and lower North Island.
Above: An unusual moth that feeds exclusively on Olearia odorata is Pseudocoremia cineracia.
The elongate, dark larvae feed on fresh foliage of the host. The moth is found in western and Central Otago northwards to South Canterbury.
Above: The appropriately named Meterana exquisita is a Spring-emerging noctuid moth that depends on various Olearia shrubs for sustenance.
While the moth is still reasonably common in some areas, it has disappeared from the many areas where its host plants are no longer found.
With their perfect camouflage, both the larvae (pictured here on Olearia bullata) and adults can be difficult to find.
All photos: Brian Patrick
Open SpaceTM Magazine No. 78, March 2010 © QEII National Trust