''Opodiphthera eucalypti'', the emperor gum moth, is a species of

moth Moths are a paraphyletic group of insects that includes all members of the order Lepidoptera that are not butterflies, with moths making up the vast majority of the order. There are thought to be approximately 160,000 species of moth, many of w ...

in the family

Saturniidae Saturniidae, commonly known as saturniids, is a family of Lepidoptera with an estimated 2,300 described species. The family contains some of the largest species of moths in the world. Notable members include the emperor moths, royal moths, and gi ...

native to Australia. This species was formerly placed in the genus ''

Antheraea ''Antheraea'' is a moth genus belonging to the family Saturniidae. The genus was erected by Jacob Hübner in 1819. Several species of this genus have caterpillars which produce wild silk of commercial importance. Commonly called "tussar silk", t ...

''.

Distribution

The emperor gum moth may inhabit all states of Australia, however it is scarce in the more southerly states where the climate is less suitable. They are also found as an introduced species on both the North and South Islands of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

Caterpillars

Caterpillars can usually be found on young adult leaves between October and March (the Australian

Spring Spring(s) may refer to: Common uses * Spring (season) Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of ...

and Summer). When the

caterpillars Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths). As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Symp ...

hatch they are black with short hairs on top of small nodes on their bodies called

tubercle In anatomy, a tubercle (literally 'small tuber', Latin for 'lump') is any round nodule, small eminence, or warty outgrowth found on external or internal organs of a plant or an animal. In plants A tubercle is generally a wart-like projection ...

s. The

hairs Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and f ...

are not poisonous and will not sting. As the caterpillars mature they change color each time they shed their

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...

(which totals to five stages in the caterpillar's appearance). The fully grown caterpillars are usually found on the highest branches of the host tree where the leaves are the youngest and easiest to digest. By the final stage before pupation the caterpillars have developed striking coloration, having a yellow/cream stripe down their bright green/blue body and nodes of red and blue. Despite this they are still surprisingly hard to spot. The caterpillar stage in the emperor gum moth's life cycle can last for many weeks, depending on the

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

and

weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur in the lowest layer of the planet's atmos ...

conditions.

Cocoon

When the caterpillar is fully mature it spins a dark brown

silk Silk is a natural protein fiber, some forms of which can be woven into textiles. The protein fiber of silk is composed mainly of fibroin and is produced by certain insect larvae to form cocoons. The best-known silk is obtained from the ...

en 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 A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

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. 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 Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindwi ...

. The effort to release itself from the cocoon is vital for its

wings A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expre ...

to expand and dry after emerging. Pupae cut from the cocoon will hatch, but the moths' wings will never expand.

Adult moths

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 larger than males. The furry 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 Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definiti ...

formation. The antennae of the males are feathery, while the females' are thinner and with fewer hairs.

Biological significance

This insect was the first used in the successful development of continuous insect

cell cultures Cell culture or tissue culture is the process by which cells are grown under controlled conditions, generally outside of their natural environment. The term "tissue culture" was coined by American pathologist Montrose Thomas Burrows. This tec ...

. Dr. Thomas D. C. Grace, a researcher with CSIRO, developed four cell lines from the ovaries of this insect and reported on them in 1962. This was a significant breakthrough since efforts to grow insect cells in culture had been attempted for decades previously. Modifications of the medium used in these efforts, Grace's insect medium, is still in use today for growing many of the insect cell lines that have since been developed (approximately 600 distinct cell lines from more than 125 insect species).

References

Wildlife of Sydney - Fact File - Emperor Gum Moth

Forest Health Fact Sheets 9 Emperor Gum Moth

Additional images

Image:Emperor Gum Moth eggs.jpg, Eggs after the caterpillars have hatched Image:Caterpillars@2nd&3rd stage.jpg, Caterpillars at second and third stages in their growth Image:Caterpillar shed 3rd stage.jpg, Caterpillar at fourth stage of growth. Its recently shed third stage skin is visible beside it Image:Caterpillar feeding3.jpg, Caterpillar feeding on a eucalyptus leaf Image:Caterpillar spinning cocoon.jpg, Caterpillar spinning its silken cocoon on a eucalyptus twig Image:Opodiphthera_eucalypti_in_WA.jpg, Proof of WA sighting. Taken 10 Nov 2007 in Albany WA Image:2010-01-04 moth2.jpg, An adult male emperor gum moth Image:2010-01-04 moth3.jpg, An adult female emperor gum moth Image:2010-01-04 moth1.jpg, An adult emperor gum moth {{Taxonbar, from=Q2454203 Opodiphthera Moths of Australia Moths of New Zealand Moths described in 1864