Gadira petraula (Meyrick, 1883)
Gadira petraula (Meyrick, 1883)
Current DoC threat status
Naturally Uncommon.Recognition / similar species
Very similar to Gadira leucophthalma, and on Banks Peninsula the two species can be found together. The forewing dorsum (trailing edge) is mostly unicolorous whitish to grey in G. leucophthalma, whereas it is patterned in grey and black in the slightly smaller G. petraula. Gadira petraula has a short-winged female in contrast to G. leucophthalma.Known distribution and abundance
Northeastern South Island south to Banks Peninsula. A localised and generally uncommon species. Coastal rocks to montane rocky sites at 400m on Port Hills, Banks Peninsula, to low alpine rocky ridges at 1300m on Seaward Kaikoura Range.Habitat
Rocky places from steep rock faces to mountainous rocky ridges and pavement, all with a cover of lichens.Host-plant and biology of early stages
Larvae live behind a curtain of silk and lichen on rock substrate, where the larvae feed on lichens. The pupa is formed in the feeding place, and adults appear not to stray far from this habitat.Flight period (months of year) and behaviour of adult
Adults have been found from mid October to early November at coastal to montane sites, but in December in the low alpine habitats of the species.Potential monitoring technique(s)
Difficult to monitor as the species is rarely found. One known site at Sumner, Port Hills is suitable for monitoring of larval feeding signs, using the conspicuous webbing of the mature larvae as an indicator. Suggested timing would be September and a standardised count over a certain area of rock face should produce comparative data that could be used to detect the trend in population numbers.Threats
Loss of habitat. Following the devastating Christchurch earthquakes in 2010-2011 much rock face habitat has been either naturally destroyed or destroyed by man to decrease the threat of unstable rock face to people and buildings in the Port Hills area. Some of this will have been inhabited by Gadira petraula. Its habitat in Sumner has been degraded severely by the earthquake but it was still present there in 2012.
In the past road-making, farming practices and stock rubbing against rocks will have compromised its habitat and fragmented its populations. This is exacerbated by its having a flightless female, which limits the species’ dispersal.