T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Caterpillar of the Gum Emperor Moth (Opodiphthera eucalypti)

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Suborder: Ditrysia
Family: Saturniidae
Genus: Opodiphthera
Species: Opodiphthera eucalypti
Common name: Emperor Gum Moth caterpillar

The Emperor Gum moth, Opodiphthera eucalypti, is a large hairy nocturnal species of moth native to Australia and were introduced to the North and South Islands of New Zealand about 1939 .
The moths live for no more than a couple of days and they never eat.. They lay their eggs on a leaf either singly or several in a row. The eggs are pale cream in colour and are approx 2mm in length.

The Caterpillars
They hatch between 7-10 days after being laid. This Caterpillar starts off life as an instar (a developmental stage) which is dark brown, with two orange spots by the head and two yellow spots by the tail. These spots develop in later into tubercles (a small, knob-like or rounded protuberance), when the first three abdominal segments develop a conspicuous orange and yellow dorsal pattern.
The adult caterpillars are large and fat and are bluish green and have a yellow lateral line.

Host Trees
They are usually found on eucalyptus trees but are sometimes found on introduced species such as the peppercorn, silver birch, liquid amber and apricot trees and even grapevines. It has been recorded in Australiafeeding on Pinus radiata (radiata pine), although apparently only after passing the early stages on eucalypt undercoppice. (see NZ Farm Forestry website)

The Cocoon:
When the caterpillar is fully mature it spins a dark brown silken cocoon on a branch which usually has a leaf to protect it with. When spinning is complete, the caterpillar sheds its final skin and takes the form of its pupal life stage. Within a day of spinning completion, the cocoon sets to a hard waterproof shell with a rough exterior and a smooth interior wall. Air holes can be seen along the side of the cocoon indicating that the cocoon is probably otherwise airtight. The moth usually emerges from the cocoon the following year (in spring or early Summer) but depending on weather conditions can stay in the cocoon from anywhere between two and five years.
When the metamorphosis is complete, the adult moth regurgitates a fluid to soften the tough cocoon and then cuts a hole using sharp hooks on the base of each forewing. The effort to release itself from the cocoon is vital for its wings to expand and dry after emerging. Pupae cut from the cocoon will hatch, but the moths' wings will never expand.

The Adult Moth:
The emperor gum moth does not feed after it emerges from the cocoon, relying solely on the energy it stored as a caterpillar. Their adult life span is limited to a couple of weeks in which they mate, lay eggs and die. The moths, like the caterpillars, are very striking in appearance. The emperor gum moth is a very large moth, having a wingspan of 120 to 150 mm. Females are generally smaller than males. The furless wings and body are multi-colored, but are in overall tones of pale reddish/brown. The wings are decorated with four prominent 'eyes' and various other markings in a symmetrical formation. The antennae of the males are feathery, while the females' are thinner and with fewer hairs.

For photos of the moth visit: http://www.terrain.net.nz/friends-of-te-henui-group/moths/gum-emperor-moth.html




The underside of a Gum Emperor caterpillar

Copyright photo courtesy of Angela Simpson.

Closeup photo showing the eight adominal prolegs with clasping pads,

Copyright photo courtesy of Angela Simpson.

Photo of the six thoracic legs and mandibles.

Copyright photo courtesy of Angela Simpson.

The Emperor Gum Moth's hard cocoon with fresh exit hole.


The 2 year old empty cocoon.