Landcare Research - Manaaki Whenua

Landcare-Research -Manaaki Whenua

FNZ 65 - Izatha (Insecta: Lepidoptera: Gelechioidea: Oecophoridae) - Popular summary

Hoare, RJB 2010. Izatha (Insecta: Lepidoptera: Gelechioidea: Oeco­phoridae). Fauna of New Zealand 65, 201 pages.
( ISSN 0111-5383 (print), ISSN 1179-7193 (online) ; no. 65. ISBN 978-0-478-34724-1 (print) , ISBN 978-0-478-34725-8 (online) ). Published 02 Sep 2010

Popular summary

Lichen tuft moths

The moths of the genus Izatha treated in this volume have been popularly named ‘lichen tuft moths’. Most of them are beautifully camouflaged when resting on the trunks of our forest trees and shrubs, not only because of their colours, which mimic bark or lichen, but also because of the tufts of raised scales on their wings and mouthparts, which imitate the raised and irregular surface of lichens. The genus Izatha only occurs in New Zealand, and is one of our very special and diverse groups of endemic moths, with 40 species now recognised. The bright green and black species are often illustrated in popular guides to New Zealand insects; formerly these were usually considered to belong to a single species, but there are in fact 3 species (Izatha huttonii, I. peroneanella, and I. taingo), distinguished clearly for the first time in this book. Caterpillars of Izatha almost all tunnel in dead wood, where they are probably largely digesting the fungal element; one or two caterpillars have been found in bracket fungi and others are known or suspected to feed on lichens. Therefore, Izatha species form part of New Zealand’s decomposer community, which are essential for recycling the nutrients in our forests and shrublands. Despite their interesting form and ecological significance, the study of these moths has been neglected, and 15 new species are described in this volume, which represents an increase of 60% over the 25 previously known.

Amongst the most extraordinary features of Izatha described in this volume are the strange and extreme genitalia, especially of the males. The phallus (penis) is often ornamented with strong ridges bearing backward-pointing teeth, and damage presumed to be from these teeth has been observed in the female genital tract. Some females have the genital tract reinforced, presumably to minimise potential damage from the males during mating. This ‘sexual antagonism’ may have evolved as a way for the male to ‘dissuade’ the female from mating more than once, thus ensuring that his sperm fertilise her ova. However, females are known to mate more than once in Izatha! Another peculiarity of the males of some Izatha species is their possession of up to 48 sword-like spines inside the phallus, which are deposited in the female genital tract during mating. These detachable spines (the ‘deciduous cornuti’) are known from some other moths, but their function is still not understood. Males deposit all their cornuti at once, but can still mate again after this. So these little moths, often overlooked or taken for granted, have strange and fascinating sex lives that are worthy of further study.

Some Izatha species are apparently rare, and may be in need of special conservation. A small brown species (I. rigescens) was found on the Wellington coast in 1929; it has not been seen since. The pale grey I. psychra is only known from a small patch of shrubland near Lake Pukaki in the Mackenzie Country; it was formerly found at one other site where it has not been seen since the 19th century. The rather large brown I. caustopa used to be found in Wellington on certain old kotukutuku (Fuchsia) trees, where the larvae tunnelled in dead branches; it has also been found at Ohakune and Puketitiri, but only 3 have been seen in the last 70 years. Since kotukutuku is declining as a result of browsing by possums, the moth may be in trouble.