Association of the noctuid moth Ichneutica steropastis with the monocot host plants Gahnia setifolia and Gahnia xanthocarpa
Abstract
Patterns and explanations of host plant associations are diverse among insects due to the range of generalist and specialist diets. In Lepidoptera, the larvae are the prominent feeding stage of each species and are often restricted to a single host, however, the current data on food plants and host specificity outlines the need for further research. New Zealand Lepidoptera are comprised of over c. 1800 species, at least c. 1685 of which are endemic. With such a high degree of endemism, relevant information needs to be increased in order to effectively manage vulnerable and/or unknown species. Gahnia setifolia and Gahnia xanthocarpa (Poales: Cyperaceae), monocotyledonous flowering plants distributed throughout the North and South Islands, have c. four known Lepidopteran associates. Dodonidia helmsii (Lepidoptera; Nymphalidae: Satyrinae) is a notable species which utilises Gahnia spp. in the northern part of its’ range, however, little information is available regarding other Lepidopteran fauna which consume the same plants. By sampling and rearing larvae observed on G. xanthocarpa and G. setifolia, Ichneutica steropastis (Lepidoptera: Noctuidae) was discovered and confirmed as sharing a host plant association. This endemic moth is commonly known for the notching damage it causes to the leaves of its original host, Phormium tenax (Asparagales: Asphodelaceae).