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Puriri moth - Aenetus virescens

By N A Martin (2010, revised 2018)

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Click to collapse Classification Info

Arthropoda

Insecta

Lepidoptera

Hepialidae

Aenetus virescens (Doubleday, 1843)

Click to collapse Common names Info

Puriri moth

Click to collapse Synonyms Info

Hepialus virescens Doubleday, 1843

Click to collapse Biostatus and distribution Info

This endemic moth is found throughout the North Island of New Zealand. It occurs in habitats with dead wood with suitable fungi for its young caterpillars and living host trees in which the larger caterpillars live in tunnels and graze callous tissue.

Conservation status: The moth occurs in natural ecosystems and parkland where suitable trees and litter and dead branches occur. It can live in adventive and cultivated trees.

Click to collapse Life stages and annual cycle Info

Moths may emerge any month of the year, although the peak months are October to December, with a second minor peak in March. The female moth, the largest moth in New Zealand, has a wing span up to 150 mm; the male is smaller with a wing span of 100 mm. Moths mainly fly in the evening. Male moths are more likely to be seen at lights.

The moths are usually green, but the intensity of colour and wing patterning is very variable. The markings of the male's forewings are white and the hind wings are greener than those of the female. Colour variations from blue-green, yellow, red and albino have been recorded. See a 2017 paper in The Weta by Graham and Care for photographs of some of the variable wing patterns and colours.

Eggs and litter phase caterpillars

After mating, the female moth scatters eggs over the forest floor. Up to 2000 eggs may be laid. The eggs are round and pale yellow when first laid, turning black a few days later. After 12-14 days, litter phase caterpillars hatch from the eggs. The litter phase caterpillars live on the underside of bracket fungi or fungal fruiting bodies encrusting twigs and branches. They make a tunnel and feed on the fungal fruiting body, and cover their feeding areas with web covered in frass (insect droppings). The fungus feeding stage lasts two to three months, during which the caterpillar may moult (change its skin).

Transfer phase caterpillars

At the end of the litter phase, it moults (changes its skin) to a darker transfer phase caterpillar. These caterpillars locate trees, which they climb, and bore through the bark into the wood of the trunk or branch. They form a distinctive seven-shaped tunnel. The top of the ‘seven’ follows the radius of the trunk/branch and slopes upwards. The longer part of the burrow descends vertically and is where the caterpillar rests. The opening of the burrow and the area used for feeding are covered with a protective web.

Tree phase caterpillars

The transfer phase caterpillar moults to a paler tree phase caterpillar, This caterpillar is a delicate transparent purplish-pink with a hardened dark-brown head capsule. It grazes on live callus tissue that develops round the opening of the burrow. Some frass is used in the web cover, but is ejected through a hole at the bottom of the web covering. As the caterpillar grows, it enlarges its burrow. It extends the radial burrow and makes a larger vertical burrow. The establishment burrow may become blocked with frass. The mature caterpillar can grow to about 100 mm long and 15 mm in diameter. The tree phase caterpillar can live up to five years, but this stage may be as short as eight months. The mean time for male caterpillars is about two years and for females, about three years.

Pupation and moth emergence

When the caterpillar has reached full size, it first removes pieces of the web covering the feeding scar. It may make many small holes or remove the entire central portion of the web. Then the caterpillar blocks the top of the vertical burrow with a fibrous disc and pupates.New pupae may be found in every month from March to November. Pupal duration is shortest for those formed in October and November, but the mean duration is 151 days for males and 173 days for females. When the moth is ready to emerge, the pupa wriggles up the shaft, pushes up the disc and protrudes through the camouflaging web. Movement up the shaft is helped by 12 horny ridges, armed with hooklets, on the upper side of the abdomen and five similar ridges on the underside. It is not known how male and female moths find each other before mating.

Click to collapse Recognition Info

The moth’s large size and distinctive colouring makes it easily recognisable. The characteristic damage to trees also makes the presence of old feeding sites easy to recognise. Active feeding sites are less easy to detect because of the camouflaged webbing. The fungal-feeding, litter phase caterpillars are the most difficult stage to detect because potential sites are more difficult to find unless deliberately sought out and because the feeding sites are covered by webbing.

Click to collapse Natural enemies Info

Pathogens and predators of puriri moths are known, but no parasitoids have been found.

Predators

Moreporks (ruru, small owls) and native bats are reported to catch flying moths. Possums and cats will also eat moths. Kaka tear at wood to try to reach caterpillars in tree branches. Dr. Miller reports that Maori also used puriri moth larvae which they called ngutara, a name also used for other wood-boring larvae.

Pathogens

Dr Grehan in his extensive study of puriri moth found three fungi and bacterium, Bacillus sp., infesting caterpillars and pupae. The only definitely named fungus, Cordyceps bassiana kills the caterpillars and forms a mass of fluffy white fruiting body extending over the larval feeding area. One unnamed fungal disease kills larvae and pupae, while another unnamed species kills pupae and forms distinctive forms finger-like coremia that protrude out of the tunnel.

Table: Natural enemies of Puriri moth, Aenetus virescens (Lepidoptera: Hepialidae), from Plant- SyNZ database (19 May 2015). The reliability index shows the quality of evidence for the host association (0-10, 10=high quality).
Scientific NameCommon NameClassificationEnemy TypeReliabilityBiostatus
Bacillus sp. (milky disease)Milky disease (Bacterium)Bacillales: Paenibacillaceaepathogen7endemic
Cordyceps bassiana Z.Z. Li, C.R. Li, B. Huang & M.Z. Fan, 2001 (Fungus)Hypocreales: Cordycipitaceaepathogen10native
Cordyceps gunnii (Berk.) (Fungus)Hypocreales: Cordycipitaceaepathogen7native
Ophiocordyceps robertsii (Hook.) (Fungus)Hypocreales: Ophiocordycipitaceaepathogen1native
Felis catus Linnaeus, 1758Cat (Mammal)Carnivora: Felidaepredator10adventive
Mustela erminea Linnaeus, 1758Stoat (Mammal)Carnivora: Mustelidaepredator10adventive
Mystacina tuberculata GrayShort-tailed bat (Mammal)Chiroptera: Mystacinidaepredator10endemic
Nestor meridionalis (Gmelin, 1788)North Island kaka (Bird)Psittaciformes: Nestoridaeomnivore10endemic
Ninox novaeseelandiae (Gmelin, 1788)Morepork (Bird)Strigiformes: Strigidaepredator10endemic
Rattus exulans (Peale, 1848Polynesian rat (Mammal)Rodentia: Muridaeomnivore10adventive
Trichosurus vulpecula (Kerr, 1792)Possum (Mammal)Marsupialia: Phalangeridaeomnivore10adventive
Vespula germanica (Fabricius, 1793)German wasp (Wasp)Hymenoptera: Vespidaepredator9adventive

Click to collapse Host plants Info

The newly hatched (neonate) caterpillars live on fungi. Larger caterpillars live in the trunk and branches of a wide variety of trees and shrubs. Host plants include native, naturalised, and cultivated species.

The caterpillar damages the tree by making radial and vertical burrows in live wood, in which the body of the caterpillar rests. At the entrance to the burrow, they graze on the cambium, forming a diamond-shaped feeding scar. They cover the scar and burrow with a tough web that is coloured like the bark of the tree. After the moth has left the pupa, the hole may grow over or remain open. The vertical burrows remain after the caterpillar has left and the defect reduces the usefulness of the wood as a timber. Heavy infestations can weaken the tree, especially those with thin trunks.

Caterpillars can also infest non-host trees, such as cherry (Prunus) and Eucalyptus. The caterpillar is killed by gum flooding the burrow.

Table: Host plants of the Puriri moth, Aenetus virescens (Lepidoptera: Hepialidae) from Plant-SyNZ database (16 May 2016). The reliability score shows the quality of evidence for the host association (1-10, 10=high).
Common Name(s)Scientific NameFamilyReliability IndexBiostatus
Smoky bracketBjerkandera adusta (Willd.: Fr.) Karst.Meruliaceae10non-endemic
 Echinochaete russiceps (Berk. & Broome) D.A. ReidPolyporaceae10non-endemic
 Fomes hemitephrus (Berk.) CookePolyporaceae10non-endemic
 'Irpex' sp.Steccherinaceae7unknown
 Junghuhnia nitida (Pers.) RyvardenSteccherinaceae10non-endemic
 Phellinus ferreus (Pers.) Bourdot & GalzinHymenochaetaceae10non-endemic
 Schizopora nothofagi (G. Cunn.) P.K. Buchanan & RyvardenSchizoporaceae10endemic
 Tremella sp.Tremellaceae7unknown
Blackwood, Tasmanian blackwoodAcacia melanoxylon R.Br.Leguminosae8naturalised
New Zealand ash, Tapitapi, Tītoki, Tītongi, Tokitoki, Tongitongi, TopitopiAlectryon excelsus Gaertn.Sapindaceae10endemic
Wineberry, Mako, MakomakoAristotelia serrata (J.R.Forst. & G.Forst.) W.R.B.OliverElaeocarpaceae10endemic
Buddleia, Butterfly bush, Summer lilacBuddleja davidii Franch.Scrophulariaceae10naturalised
Marble leaf, Motorbike tree, Kaiwētā, Piripiriwhata, Punawētā, Putaputawētā, PutawētāCarpodetus serratus J.R.Forst. & G.Forst.Rousseaceae10endemic
Beefwood, She-oakCasuarina sp.Casuarinaceae7unknown
Kākawariki, Kanono, Kapukiore, Karamū-kueo, Kueo (fruit), Manono, Pāpāuma, Raurēkau, ToherāoaCoprosma grandifolia Hook.f.Rubiaceae5endemic
Tree tutu, Pūhou, Tāweku, Tūpākihi, TutuCoriaria arborea Linds.Coriariaceae5endemic
Bentham's cornel, Himalayan strawberry tree, Strawberry dogwoodCornus capitata Wall.Cornaceae10naturalised
CotoneasterCotoneaster glaucophyllus Franch.Rosaceae10naturalised
Hawthorn, Neapolitan medlar, White hawthornCrataegus monogyna Jacq.Rosaceae10naturalised
Cedar of Goa, Mexican cypress, Portuguese cypressCupressus lusitanica Mill.Cupressaceae8naturalised
Red escalloniaEscallonia rubra (Ruiz & Pav.) Pers.Escalloniaceae8naturalised
Brown barrel, Cut tailEucalyptus fastigata H.Deane & MaidenMyrtaceae6naturalised
Giant gum, Mountain ash, Stringy gum, Swamp gumEucalyptus regnans F. Muell.Myrtaceae8naturalised
Sydney blue gumEucalyptus saligna Sm.Myrtaceae10naturalised
Common beech, European beechFagus sylvatica L.Fagaceae10cultivated
Ash, Common ash, European ashFraxinus excelsior L.Oleaceae10naturalised
Red beech, Hutu, Hututawai, Raunui, Tawai, TawhaiFuscospora fusca (Hook.f.) Heenan & SmissenNothofagaceae10endemic
Black beech, Tawhai raurikiFuscospora solandri (Hook.f.) Heenan & SmissenNothofagaceae10endemic
Hard beech, Hutu, Hututawai, Tawhai raunuiFuscospora truncata (Colenso) Heenan & SmissenNothofagaceae10endemic
Broadleaf, Huariki (fruit), Kāpuka, Māihīhi, Pāpāuma, Paraparauma, TapatapaumaGriselinia littoralis RaoulGriseliniaceae10endemic
Akakōpuka, Akapuka, Puka, PukateaGriselinia lucida G.Forst.Griseliniaceae10endemic
Lacebark, Hohere, Hoihere, Houhere, Houhi, Houhi ongaonga, Houī, Ongaonga, Whauahi, WheuhiHoheria populnea A.CunnMalvaceae10endemic
Graceful lacebark, Lacebark, Houhere, HouhiongaongaHoheria sexstylosa ColensoMalvaceae10endemic
Black walnut, California walnutJuglans nigra L.Juglandaceae10cultivated
White tea tree, Kānuka, Kōpuka, Manuea, Mānuka, Mānuka-rauriki, Mārū, Rauiri, RauwiriKunzea ericoides (A.Rich.) Joy Thomps.Myrtaceae10non-endemic
Red tea tree, Tea tree, Kahikātoa, Kātoa, Mānuka, Pata, Rauiri, RauwiriLeptospermum scoparium J.R.Forst. & G.Forst.Myrtaceae10non-endemic
Tall mingimingi, Hukihukiraho, Kaikaiatua, Mānuka-rauriki, Mikimiki, Mingi, Mingimingi, Ngohungohu, TūmingiLeucopogon fasciculatus (G.Forst.) A.Rich.Ericaceae10endemic
Broadleaf privet, Tree privetLigustrum lucidum W.T.AitonOleaceae10naturalised
Chinese privet, Small-leaf privetLigustrum sinense Lour.Oleaceae10naturalised
Silver beech, Tawai, TawhaiLophozonia menziesii (Hook.f.) Heenan & SmissenNothofagaceae10endemic
Apple, Crab-appleMalus ×domestica Borkh.Rosaceae10naturalised
Whiteywood, Hinahina, Inaina, Inihina, Māhoe, Moeahu, KaiwetaMelicytus ramiflorus J.R.Forst. & G.Forst.Violaceae1non-endemic
NgaioMyoporum laetum G.Forst.Scrophulariaceae10endemic
Coastal maire, MaireNestegis apetala (Vahl) L.A.S.JohnsonOleaceae10non-endemic
Black maire, Maire, Maire raunui, PauNestegis cunninghamii (Hook.f.) L.A.S.JohnsonOleaceae10endemic
White maire, Maire, Maire raunui, Maire raurikiNestegis lanceolata (Hook.f.) L.A.S.JohnsonOleaceae10endemic
Narrow-leaved maire, Maire kōtae, Maire rauriki, Maire roro, Maire rōroro, RōroroNestegis montana (Hook.f.) L.A.S.JohnsonOleaceae10endemic
OliveOlea europaea L.Oleaceae10naturalised
Akewharangi, Heketara, Ngungu, Taraheke, Tātaraheke, Wharangi-piroOlearia rani (A. Cunn.) DruceCompositae5endemic
 Paulownia elongata S.Y. HuPaulowniaceae10cultivated
Ahikōmau, Hine-kaikōmako, Kahikōmako, KaikōmakoPennantia corymbosa J.R.Forst. & G.Forst.Pennantiaceae5endemic
New Zealand hazel, Nonokia, Nonorangi, TainuiPomaderris apetala Labill.Rhamnaceae10non-endemic
CherryPrunus sp. 'cherry'Rosaceae4naturalised
Alpine pepper tree, Mountain horopito, Pepper tree, Red horopito, Horopito, ōramarama, RamaramaPseudowintera colorata (Raoul) DandyWinteraceae10endemic
Common oak, English oak, Oak, Truffle oakQuercus robur L.Fagaceae10naturalised
Red oakQuercus rubra L.Fagaceae10naturalised
Westland quintiniaQuintinia acutifolia KirkParacryphiaceae7endemic
Quintinia, Kūmarahou, TāwheowheoQuintinia serrata A.Cunn.Paracryphiaceae10endemic
 Raukaua simplex (G.Forst.) A.D.Mitch., Frodin & Heads var. sinclairii (Hook.f.) A.D.Mitch., Frodin & HeadsAraliaceae10endemic
Evergreen buckthorn, Italian buckthornRhamnus alaternus L.Rhamnaceae10naturalised
English elmUlmus procera Salisb.Ulmaceae10cultivated
New Zealand oak, Kauere, PūririVitex lucens KirkLabiatae10endemic
Kāmahi, Tawhero, TōwaiWeinmannia racemosa L.f.Cunoniaceae5endemic

Click to collapse Control Info

Puriri moths are part of the biodiversity of native ecosystems. Where host trees grow in native ecosystems, the moth should be accepted. There are, however, some circumstances where control could be justified.

For single specimen trees, puriri moth caterpillars can be killed by injecting insecticide into their burrows.

In orchards and tree collections, the risk of infestations can be reduced by keeping the ground clean of any dead wood on which fungi can grow and develop. This prevents the young fungal-feeding litter phase caterpillars from establishing. For information about reducing risk to forest trees go to www.nzffa.org.nz/farm-forestry-model/the-essentials/forest-health-pests-and-diseases/Pests/Puriri-moth/Puriri-mothEnt16

Click to collapse Additional information Info

Behaviour of moths

It is not known how male and female moths find each other for mating. The male moth has brush organs on the tibia of the hind leg. Other moths of the family Hepialidae that have brush organs show courtship; the males fly in groups at dusk and the females fly to them for copulation. It is believed that the males emit a pheromone that attracts the female moths. Mating has not been observed for puriri moths, but probably occurs after dark.

Sometimes many male moths gather at lights at night. Is emergence of moths synchronised and if so how?

Insects associated with pupal skins

When a moth leaves its pupal skin, it excretes all the waste that has accumulated during the pupal stage. An intact pupal skin with brown waste liquid present had hover fly larvae living in it. Several kinds of hover fly have larvae that live in wet decaying matter. The adult female fly was probably attracted to the smell of the waste liquid.

Insects associated with empty tree burrows

Other insects and spiders colonise the vacated puriri moth burrows. Some insects such as weta are reported to stop the tree growing over the hole by chewing the edge of the opening. Māori knew that weta inhabited puriri moth burrows and named Carpodetus serratus putaputaweta, because it often had many weta living in it.

Impact on North Island beech forests

In the North Island, puriri moths cause damage to beech trees. The damage to the wood lowers the value of beech as a timber tree in the North Island and makes it less valuable to fell. Through its damage to the timber, did puriri moth save many North Island beech forests from clear felling?

Click to collapse Bug signs Info

Metal outdoor signs are available for placement in reserves, Regional and National parks, urban parks and school grounds. They can be bought from Metal Images Ltd, www.metalimage.co.nz/products/botanic-labels. The Bug Signs are listed near the bottom of the ‘Fauna Species list’. The signs come in two sizes, 100 x 200 mm, 194 x 294 mm. The signs can be bought ready mounted on a stand that needs to be ‘planted’ in the ground, or they can be bought unmounted with holes for fixing into your own mounts.

The signs for Puriri moth are best placed near trees with the distinctive damage to trunks and/or branches. Trees commonly, exhibiting damage include, puriri, lacebark (Hoheria species) and Carpodetus serratus (Marble leaf, Putaputawētā). Trees with puriri moth damage usually live for many years.

Click to collapse Information sources Info

Dugdale JS 1994. Hepialidae (Insecta: Lepidoptera). Fauna of New Zealand 30: 1-164.

Early J 2009. Know your New Zealand insects & spiders. Northcote, Auckland, New Zealand, New Holland Publishers (NZ) Ltd. 176 p.

Grehan JR 1987a. Life cycle of the wood-borer Aenetus virescens (Lepidoptera: Hepialidae). New Zealand Journal of Zoology 14: 209-217.

Grehan JR 1987b. Evolution of arboreal tunnelling by larvae of Aenetus (Lepidoptera: Hepialidae). New Zealand Journal of Zoology 14: 441-462.

Grehan JR 1988. Fungal and vascular plant polysaccharide digestion by larvae of Aenetus virescens (Lepidoptera: Hepialidae). New Zealand Entomologist 11: 57-67.

Grehan JR 2009. Ghost moth (Lepidoptera: Hepialidae) research and discovery in the Southwest Pacific. Bulletin of the Buffalo Society of Natural Sciences 38: 17-29.

Grehan JR, Care C. 2017. Colour pattern variation in puriri moth, Aenetus virescens (Lepidoptera: Hepialidae). The Weta 51: 51-57.

Grehan JR, Wigley PJ 1984. Fungal and bacterial diseases of puriri moth, Aenetus virescens (Lepidoptera: Hepialidae), larvae. New Zealand Entomologist 8: 61-63.

www.nzffa.org.nz/farm-forestry-model/the-essentials/forest-health-pests-and-diseases/Pests/Puriri-moth/Puriri-mothEnt16 (describes impact on wood quality).

www.nzffa.org.nz/farm-forestry-model/the-essentials/forest-health-pests-and-diseases/Pests/Puriri-moth/Puriri-MothFHnews162 (early reports of puriri moth damage to trees).

Plant-SyNZ: Invertebrate herbivore-host plant association database. plant-synz.landcareresearch.co.nz/.

Click to collapse Acknowledgements Info

John Grehan for photographs and illustrations.

John Bain for providing the photographs from Scion

Robert Hoare for photographs of moths and information.

Ruud Kleinpaste for a photograph of a moth.

Eric Scott for helpful suggestions.

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.

Landcare Research New Zealand Limited (Landcare Research) for permission to use photographs.

New Zealand Forest Research Institute Limited (Scion) for permission to use photographs.

Click to collapse Other images Info

Click to collapse Update history Info

1 April 2018. NA Martin. Bug signs updated

16 October 2017. NA Martin. Life Stages and Annual Cycle and Information sources: a new sources of photographs of moths added.

6 June 2016. NA Martin. Recognition: added photos of moth and external tree damage. Other Images: images added. Host plants: names of host fungi added. Natural enemies: list of pathogens and predators added. Details of Bug Signs added.

26 July 2010. NA Martin. Caption for Image\3CL: female to male. Annual cycle: added pre-pupation web removal by caterpillar.

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