Why moths matter

Opinion: Morgane Merien explains why we need to start recognising the importance of these fascinating little insects and their vital role in the ecosystem.

New Zealand's beautiful puriri moth, an adult wingspan can reach 15cm. Photo: Wikipedia/creative commons licence

Moths, they generally go unnoticed except when they flit annoyingly around your lights. They don’t attract much public interest and there is little understanding of the effects introduced species and competitors have had on our natural landscape.

But there is a lot more to moths than their lamplight fluttering, and this is what we celebrated during National Moth Week, a worldwide annual event about everything moths which finished on Sunday. This event encourages people to learn about and document moths where they live. It has been running for 10 years and Aotearoa New Zealand is participating for the first time.

While most people are familiar with butterflies and think of moths as a nuisance, they are in the same family – Lepidoptera (from the Ancient Greek, meaning wings with scales). However, the overwhelming majority of our Lepidoptera species in New Zealand are moths.

In New Zealand, we have around 2000 species of moth (pūrerehua), most of which are endemic (around 90 percent) and found nowhere else in the world. Some moths fly at night and some fly during the day. Summer brings out the highest numbers of moth species in New Zealand, but winter is the only time you will see others, like the trans-winter owlet moth, the olivine gem moth and several species of case moths.

Moths can be found in most habitats with some locations housing more than 400 species. They inhabit every kind of land-based ecosystem and there are even pond moths. Across the highest mountains, moths inhabit lichens, mosses, herbs and grasses; they live in forests, coasts, grasslands, wetlands, cliffs and front lawns. Name a habitat and moths will form part of how the ecosystem functions.

Adult moths are short-lived, one-to-two weeks for most, so adults must quickly find a mate and females must locate a place to lay their eggs. Larvae (caterpillars) hatch from the eggs, grow and then, in a remarkable process (metamorphosis) carried out inside a pupa life stage, their body tissues change to form delicate winged adult moths. The largest adults can have wingspans up to 15cm (the pūriri moth), with the smallest species having wingspans of just 2mm (leaf-mining moths).

Some moths are small and brown, but other are very beautiful and quite striking. One only needs to take a closer look and see the diversity in patterns and colours. Some moths are considered pests but on the whole, there are far more species beneficial to the planet than harmful. However, due to their nocturnal habits and their small size, they can be often ignored and misunderstood. This can lead to far-reaching consequences, especially when we consider the significant roles moths play in our environment.

Moths are incredibly important, both for their intrinsic value and the services they provide to our planet. Their deep history helps us to elucidate the history of how New Zealand developed geologically, and how our flora and fauna evolved through time.

Both adults and caterpillars are a major source of food for many different animals including birds, spiders, bats, and other insectivorous critters. Even humans eat them! For example, the silkworm pupa is a street snack in Korean cuisine called beondegi and in parts of Southern Africa the mopane caterpillar, which turns into a type of emperor moth, is a huge source of protein and tinned mopane ‘worms’ can be found in in supermarkets

Moths are also important indicators of a healthy environment and ecosystem. Their presence often indicates the habitat is rich in other critters and a good place to live. Pūrerehua play a key role in nutrient and carbon cycling – caterpillars break apart coarse organic matter, enriching soils. Lastly, moths are important pollinators in our ecosystems, as they help seed production of plants when feeding on the nectar or pollen of flowers. What’s more, moths around during winter such as the aptly named trans-winter owlet moth provide a ‘winter pollination service’ for winter flowering plants in native forests.

Interestingly, moths can be tightly linked to their host plants, often spending their whole lifecycle on one plant. There are still many New Zealand moths where no one knows what plant its caterpillars need to feed on. Many keen naturalists collect pieces of plant that have caterpillars feeding on them, patiently rear them till they form a pupa and then wait to see what adult moth emerges a month or so later.

Like many of our other native insects, moths can have weird habits. A peculiar characteristic of some of our moths is being flightless. This is usually the female who will hang out on vegetation waiting for the males to find her. For example, one of our winter moths, the case moths in the genus Reductoderces. The female has no need to fly and instead, uses a trick common among moths of wafting a unique scent or pheromone. Males, with a wingspan of only a few millimetres, must fly along the scent trail to find the female for mating.

There are species of moth unique to many parts of the country but being so secretive in the middle of winter, many of them are still to be discovered and named.

So, in short, we need to start recognising the importance of these fascinating little insects and their vital role in the ecosystem. Moths are a part of nature and have as much a right as any others to thrive and be nurtured. And when we look after our insects, the environment benefits and so do we.

The New Zealand Entomological Society has organised events around the country to mark Moth Week and online depository iNaturalist has a project to help map the geographical distribution of our moths and provide more information about their biodiversity.

So, get out there and document all you can - happy mothing!

Morgane Merien acknowledges the help of DOC science adviser Eric Edwards, and Dr Sheri Johnson, Department of Zoology, University of Otago, in writing this article.

Morgane Merien is a doctoral candidate in School of Biological Sciences.

This article reflects the opinion of the author and not necessarily the views of the University of Auckland.

Used with permission from Newsroom Why moths matter 28 July 2021.

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