Ornate case moths – Reductoderces
The coldest mornings can bring out the coolest creatures
It’s international moth-week and you might think great for northern hemisphere summer but a little chilly for delicate moths to be on the wing here.
That is mostly true, but nature always has exceptions. Ornate case moths are a case in point. Across Aotearoa in the winter, case moths in the genus Reductoderces are emerging as adults from their little green silken cases. A still frosty morning at dawn is the best time to see them. Hidden flightless females on a mossy green branch or an algae matted rockface will be hanging from their cases. With no need to fly, they are using a trick common among moths – wafting a unique scent or pheromone. Males with a wingspan of only a few millimetres must fly along that scent trail to find a female for mating. There are species 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.
For more information:
Trans-winter owlet moth – Meterana vitiosa
Trans-winter because these moths come out right through the winter months, although not that you’d know it. These owlets (Meterana vitiosa) have a 37mm wingspan and shades of green and black on dark brown forewings. That’s hard enough to see in a forest, but reflecting their name, they are night active. But if you were in forest with a bright light on a mild winter’s night they can be common. This is because their caterpillars feed on native coprosma shrubs in the forest shade. And coprosmas are common with so many different ‘tasty’ species to choose from. And note there are plants -even coprosma species – that are winter flowering, and so these moths can provide a ‘winter pollination service’ in native forests.
Olivine gem moth – Ichneutica peridotea
Tāmaki Makaurau Auckland’s olivine gem moth
This beautiful moth was only named two years ago. Partly because of its winter flight period from July to September, but also, because while naming things is cool and purposeful, there are currently few experts actively documenting Aotearoa’s insect fauna. The olivine gem moth was named Ichneutica peridotea because of the rich green patterning of its wings, like the olivine green gem stone peridot. Right now, olivine gem moths are only known from the Auckland area and only one female has ever been seen. But there is a good chance it will be discovered in adjacent regions and parts of Northland. Who knows, maybe someone will share a picture of it during moth week. Another unknown thing about this moth is that no one knows what its caterpillars do for a living? Many moths and butterflies are fussy about what their caterpillars can eat, and olivine gem moth may be another example. If we want to protect unique species like this, then it is critical to protect the places where you find them. But better still, to know what species of plant host the caterpillar needs and protect those plant populations. Finding and naming this moth is really just a start, nature still needs mystery solving people.
More information: Hoare R.J.B. (2019) https://www.landcareresearch.co.nz/uploads/public/Publications/Fauna-of-NZ-Series/FNZ73_Hoare_SQ.pdf
Pond moths – Hygraula nitens
Pond moths live near you
People monitoring freshwater health often look at the array of insects surviving in streams and lakes as an indicator of healthy freshwater habitats. Such monitoring people know pond moth Hygraula nitens quite well. It is New Zealand’s only moth with a caterpillar that lives in water. It is also one of our most widespread moths as it lives nationwide, including the Chatham Islands. Caterpillars are particularly ugly as they are covered in gill structures. Caterpillars eat a range of native and introduced aquatic plants while hiding in a retreat made from plant pieces. Much less frequently noticed, but certainly more attractive, are adults. Partly this is because adults are not all that big (25mm wingspan), and are attracted to lights at night.
Because they are in pond waters everywhere, and many of us live near slow moving streams, then almost certainly the pond moth lives near you. They are hardy animals that cope reasonably well with nutrient pollution in waterways, as nutrient enrichment often results in dense aquatic plant growth in slow flowing soft bottom habitats. Because these little moths thrive on invasive aquatic plants as well as native ones, they are an example of nature adapting and persisting in our own urban and rural back yards.
Winterbourn M.J. et. al. 2006. https://ento.org.nz/product/aquatic-guide/
Redikop P. et. al. 2018. https://link.springer.com/content/pdf/10.1007/s10750-016-2709-7.pdf
Ghosts in the swamp: A winter moth story
Ghost moths are one of the more ancient families of moths worldwide, but that does not make them any less beautiful or interesting. Here in New Zealand, there are many species including our largest moth species ̶ the pūriri moth. Because ghost moths are large, their caterpillars are also large and would be a tasty treat for birds and other predators. Ghost moth caterpillars generally live in a secure retreat. For many species, this is a hole in damp ground or wetland. Adults have to take their chances to mate and disperse. Analysis of the diet of stoats living in Fiordland shows that adult ghost moths full of eggs and flipping around on the ground at night can fall victim, at least to stoats, and probably other exotic predators too. Native predators, such as ruru owls, and other now extinct birds of the night, surely got through the winter aided by winter emerging ghost moths.
There are two winter ‘bog specialists’. The bog ghost moth, Cladoxycanus minos, lives in mossy wet areas from Taranaki southwards in western and central lower North Island and much of the South Island. Adults emerge from the ground from April to June, but on the South Island west coast they emerge right through to August. The other winter species, the sphagnum ghost moth, Heloxycanus patricki, lives in peaty sphagnum moss bogs of Otago and Southland. It has a two-year lifecycle and interestingly, their populations are synchronised wherever good mossy wetlands remain, so that adults only emerge in odd numbered years. This means 2021 is a good year for putting on your gumboots if you are in Otago or Southland and looking for signs of a ghost on the bog.
Dugdale J.S. 1994. Fauna of NZ Ko te Aitanga Pepeke o Aotearoa #30, Hepialidae. https://www.landcareresearch.co.nz/uploads/public/Publications/Fauna-of-NZ-Series/FNZ30Dugdale1994.pdf
Patrick 2014 Winter-emerging moths of New Zealand. https://weta.ento.org.nz/index.php/weta/article/view/166