Maoricrambus oncobolus (Meyrick, 1885)
Maoricrambus oncobolus (Meyrick, 1885)
Current DoC threat status
Nationally Endangered.Recognition / similar species
Very similar externally to the much commoner Orocrambus harpophorus and difficult to distinguish in the field where the two occur close together. Orocrambus harpophorus has the discal white forewing streak at 2/3 hooked apically, whereas the streak is less well defined and not hooked in M. oncobolus. The frons (front of the head above the palps) in M. oncobolus has a distinct conical projection, whereas it is smooth in O. harpophorus.
Known distribution and abundance
Known from Castle Hill (type locality) and nearby Porter River, mid Canterbury, the North Branch of the Von River of northern Southland, and southern Southland. There is a single recently identified North Island specimen from flaxlands at Paiaka, near Foxton WI, collected in 1950.
Habitat
At three sites close to the Oreti River, a few kilometres west of Invercargill, the species has been repeatedly found in small areas of short turf or short grasses both beside the Oreti River and behind Oreti Beach. One site was tidal and contained a small indigenous tussock species. All these sites appear to have some connection with saltwater, which probably suppresses other vegetation and produces a diminutive sward that nurtures the moth’s own hostplant.
The exact habitat at the other localities is unknown.
Host-plant and biology of early stages
Not known.
Flight period (months of year) and behaviour of adult
South Island adults have been found between mid December and mid February with possibly a peak emergence in mid January based on 7 records. The label on the Paiaka specimen seems to indicate that it was collected in June, which is surprising. Female fully flighted.
Adults can be disturbed by day in their habitat but appear to be mainly active by night.
Potential monitoring technique(s)
A standardised light trapping regime in mid January at known habitat would be a useful tool in determining the population trend.
Threats
While much of the species’ known habitat may be protected as marginal strips around waterways, there is no management of the habitat to maintain it as suitable for the moth. Most likely these habitats continue to be degraded by human recreation, weed infestation and, at the inland Von River habitat, extensive sheep and cattle grazing.
The Porter River specimen was collected in 1977 so this locality and any other potential habitat near the type locality should be searched. Likewise, potential remaining habitat in the Manawatu area should be investigated.