Male pūriri moth

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There are many names for the largest native moth in New Zealand, and much can be gleaned from a name…

The Pūriri Moth (Aenetus virescens)

One of the grub’s main host trees is the pūriri tree (Vitex lucens) hence a common name being the pūriri moth.

The Ghost Moth

Ngāti Kahungunu (the Māori iwi located along the eastern coast of the North Island of New Zealand) tradition describes a grandson of Tāne (the god of the forest), Tūteahuru, and his wife, Hinepeke (jumping woman), producing numerous insects and lizards that dwell within the earth, on the land or stones, and in the water.

One descendant of the couple was the ghost moth (AKA the pūriri moth). As it flies at dusk and into the night – regarded as the realm of spirits – it was known as a spiritual messenger, or a ghost of an ancestor returning to visit their descendants.

The term ‘ghost moth’ confusingly refers to an entire family of moths (Hepialidae) with approximately 500 species worldwide and 28 endemic to New Zealand, the pūriri moth being one of them. This highlights the difficulty inherent in common names. Scientists and taxonomists use Latin binomial names to describe species which often clears up some of the confusion. The pūriri moth’s scientific name is Aenetus virescens.

Pepe Tuna

In the Māori language, ‘pepe tuna’ means ‘eel moth’. This name can be attributed to the practice of using the grubs as eel bait by Māori. The name may also originate from the fact that eels may feed on them while migrating between September and January.

Mokoroa

Mokoroa (long grub or caterpillar) is the Māori name for the grub of the moth, and is used in the saying:

‘He iti mokoroa e hinga pūriri’ ‘A small mokoroa can fell a pūriri tree’.

This serves the purpose of reminding us not to underestimate the impact of small things.

Ngutara and Pungoungou

As for the remaining two Māori names, Ngutara and Pungoungou, I have not been able to find any meaning behind them, but Landcare Research and T.E.R:R.A.I.N have listed them as alternative names. If you know the story behind these two names, please let us know in the comments!

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The Moth

Pūriri moths can only be found on the North Island. Amazingly, adult female moths can have a wingspan of 15cm. Although not common, they are often drawn to house and street lights near native forest. They are seen in spring and only live a few days as they lack mouth-parts. During this short period, the adults mate and the females lay up to 2000 eggs on the forest floor.

Male and female moths are different. Males are smaller than females and have white markings on their forewings (below right). Although they are usually green, some males are yellow, bluish or white. Females, on the other-hand, are larger with dark markings on their forewings (below left).

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Pūriri moths are predated upon by birds, namely kākā and ruru/morepork, as well as New Zealand native bats. Unfortunately, introduced possums and cats also have an impact on their numbers.

The Caterpillar

The newly hatched grubs/caterpillars eat fungus growing on fallen trees.

Once fattened up and considerably larger, the caterpillars search for a pūriri tree. The grubs do use other host trees in which to live. A few documented native trees include beech (Fuscospora spp.), putaputawētā (Carpodetus serratus), houhere (Hoheria spp.), mānuka (Leptospermum scoparium), lancewood (Pseudopanax crassifolius), wineberry (Aristotelia serrata) and tītoki (Alectryon excelsus). Some introduced trees have also been utilised by the caterpillars including oak, apple and willow.

They tunnel into the trunk of the tree making a 7-shaped tunnel where they eat the inner bark and outer sapwood for up to 6 years.  The caterpillars make a silk cap at the entrance to the hollow to seal themselves inside. Pupation occurs in the tunnel.

Unsurprisingly, being the largest native moth, they are also our largest native caterpillar reaching 12cm long. Māori would remove the silk caps and pour water into the hollows forcing the grub to evacuate. The grubs would then be used for food or eel bait.

Two male pūriri moths

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Seeing Them For Ourselves

I had heard a lot about this magnificent, giant, green moth, but had never laid eyes on one. This year, however, my luck was in.

During a visit to our friends’ bach in Taupo, two large green moths came hurtling through the open door almost as soon at the outside light had been turned on. Instantly, Emma and I knew what they were. Both of the moths were male.

Fast forward a few weeks and we accompanied the Natural History Curator of the  Whanganui Museum to Bushy Park for a session of light-trapping and macro work. We had many insects drawn to the trap set up on the edge of the forest next to a wetland, but it was getting late, so we headed back to the car.

Before leaving, we thought we would set up the trap one last time. We set it up in the carpark of all places. To our surprise, we were inundated with pūriri moths, including a large female. With the moths came morepork/ruru which snatched a few of them from beneath our noses.

What a treat to see both male and female pūriri moths, and to have owls swooping in to snatch the odd green morsel!

A ruru/morepork (Ninox novaeseelandiae) – An owl native to New Zealand and Tasmania

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References and Further Reading

Crowe, Andrew (2002). Which New Zealand Insect?. North Shore: Penguin. p. 44. ISBN 978-0-14-100636-9

Landcare Research – Puriri Moth Factsheet – http://nzacfactsheets.landcareresearch.co.nz/factsheet/InterestingInsects/Puriri-moth—Aenetus-virescens.html (Retrieved 11 January, 2018)

New Zealand Farm Forestry Association Website – Puriri Moth – http://www.nzffa.org.nz/farm-forestry-model/the-essentials/forest-health-pests-and-diseases/Pests/Puriri-moth/Puriri-mothEnt16 (Retrieved 11 January, 2018)

Te Ara website – Puriri Moth – https://teara.govt.nz/en/1966/moth-puriri (Retrieved 11 January, 2018)

Te Ara Website – Story: Te aitanga pepeke – the insect world: Moths – https://teara.govt.nz/en/te-aitanga-pepeke-the-insect-world/page-3 (Retrieved 11 January, 2018)

T.E.R:R.A.I.N – Taranaki Educational Resource: Research, Analysis and Information Network Website – Aenetus virescens (Puriri moth) – http://www.terrain.net.nz/friends-of-te-henui-group/moths/puriri-moth-aenetus-virescens.html (Retrieved 11 January, 2018)