From the Garden

So much of my childhood was occupied by garden explorations – trying to find the shiniest beetle, the jumpiest leaf hopper, the longest stick insect, the biggest bug… The emperor gum moth and its caterpillar were always the ultimate find. After telling these tales to Tom, he was determined to see what all the fuss was about, so we’ve had our eye out for them ever since.

We were out in the garden last week, and decided to jump the fence to check out the giant gum tree in our neighbour’s paddock. Much to our delight, hanging from one of the lower branches we found this beautiful emperor gum moth! Tom has finally seen his first one.

The emperor gum moth (Opodiphthera eucalypti) is native to Australia, but was introduced to New Zealand in the early 1900s, probably as pupae on imported hardwood poles. The caterpillars feed on eucalypts, but have been known to feed on a number of other exotic trees. It is a very large moth, having a wingspan of up to 150 mm. Females are generally larger than males. A more concrete way of determining its sex is to look at their antennae: From the feather-like antennae on this specimen, you can tell that he is male. The females have much finer antennae with fewer ‘hairs’.

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We also took a branch which had a leaf with a row of emperor gum moth eggs attached. It’s been in a vase on our kitchen bench for the last week. We’ve been eagerly checking the eggs every time we walk past and, two days ago, they finally hatched!  They are hungry, little creatures, and have been munching away.

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Already, just after these couple of days, they are noticeably bigger. We are hoping to keep them until they reach their final instar (of which there are five before they pupate). In their first two instars, they are dark, just as the one pictured above. But, in their last three instars, they have very striking colouration. They are bright greenish-blue (similar to the colour eucalypt leaves) with nodes of red and blue, and a yellow/cream stripe down their body. The fully grown caterpillar may be up to 120 mm long. You can see why children would love them! We will definitely post photos of them once they reach that stage.

If you want to find them yourself and need to know when to look, here is a life-cycle  taken from the ‘Farm Forestry NZ’ website (based on specimens living in the Manawatu):

  • In spring and early summer the adult within the cocoon regurgitates a fluid which softens the silk; it then emerges by cutting a hole with a sharp book on the base of each forewing. The moth has poorly developed mouth-parts and is unable to feed.
  • Mating occurs soon after emergence and the eggs are then laid.
  • Caterpillars are usually found from mid-December and pupate from approximately mid- January to the end of August. Some adults may emerge in late February to mid-March and produce a second generation of caterpillars, but the pupae produced in mid- January to August normally overwinter.

We’ll keep you updated!

References and Further Reading

Farm Forestry New Zealand (Retrieved 15 November 2016)
http://www.nzffa.org.nz/farm-forestry-model/the-essentials/forest-health-pests-and-diseases/Pests/Antheraea-eucalypti/Gum-emperor-mothEnt07

T.E.R:R.A.I.N – Taranaki Educational Resource: Research, Analysis and Information Network (Retrieved 15 November 2016)
http://www.terrain.net.nz/friends-of-te-henui-group/moths/gum-emperor-moth.html

“Which New Zealand Insect?”, Andrew Crowe: Penguin Books. 2002.

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