Initially the caterpillars feed in a group, eating only the surface flesh of the leaves. Later instars hide during the day in a communal shelter. For this, they use a curled dying leaf, still attached to the stem. The caterpillars leave this nest at night to feed. For feeding, a Caterpillar will lie along the edge of a leaf, and feed from the edge inwards.

Caterpillar in feeding posture
(Photo: courtesy of Merlin Crossley, Melbourne, Victoria)

The caterpillars grow to a length of about 3 cms. They pupate in individual cells in the soil. The pupal stage can last for eight months.

(Photo: courtesy of Merlin Crossley, Melbourne, Victoria)

The adult moths have light brown forewings with patches of reddish brown, especially along the hind margin, and to a lesser extent around the base. The hindwings vary from yellow to orange. The forewings have slightly recurved tips, and the hindwings have scalloped edges. The moths usually rest with the hindwings covered by the forewings, with the forewings flat like a Concord aircraft, and sometimes angled like a tent. But sometimes the hindwings are only partly covered, and the outline resembles that of a bat. The moths have a wingspan of about 4 cms.

(Photo: courtesy of CSIRO/BIO Photography Group, Centre for Biodiversity Genomics, University of Guelph)

The moth can erect a dorsal black-edged crest on the thorax.

showing crest on the thorax
(Photo: courtesy of Liam Manderson, Carwoola, New South Wales)

The underside of each forewing has a conspicuous black submarginal streak at the wing-tip.

underside
(Photo: courtesy of John Bromilow, Ainslie, Australian Capital Territory)

The species is found over most of Australia. It is a pest in forests in

eggs, magnified
(Photo: courtesy of Michael Sim, Isaacs, Australian Capital Territory)

The eggs are laid on a leaf of a food plant, in an array of 50 or so, in neat rows, some eggs doubly stacked. Initially they are pale green flattened ellipsoids, turning purplish as hatching approaches.

drawing by Achille Guenée, listed as Idiodes privata,
in Boisduval & Guenée: Uranides et Phalénites,
Histoire naturelle des insectes; spécies général des lépidoptères,
Volume 9, Part 1 (1857), Plate 14, fig. 4,
image courtesy of Biodiversity Heritage Library, digitized by Smithsonian Libraries.

The pheromones of this species have been investigated.

Attacks on trees seem to worse in plantation environments with reduced tree species variety. Research has been conducted on control :

These caterpillars have been found regularly every June for several years on a particular Mottlecah tree in a Melbourne suburb. The tree appears to be none the worse for these attacks.

Further reading :

Cathy Byrne,
Characterisation of the Australian Nacophorini and a Phylogeny for the Geometridae from Molecular and Morphological Data,
Ph.D. thesis, University of Tasmania, 2003.

Ian F.B. Common,
Moths of Australia,
Melbourne University Press, 1990, fig. 53.13, pl. 10.16, pp. 58-59, 67, 364.

Pat and Mike Coupar,
Flying Colours,
New South Wales University Press, Sydney 1992, p. 47.

R.H. Eldridge,
Autumn gum moth (Mnesampela privata),
State Forests of New South Wales, Sydney 1995.

Marilyn Hewish,
Moths of Victoria: Part 5 - Satin Moths and Allies - GEOMETROIDEA (A),
Entomological Society of Victoria, 2014, pp. 32-33.

Achille Guenée,
in Boisduval & Guenée: Uranides et Phalénites,
Histoire naturelle des insectes; spécies général des lépidoptères,
Volume 9, Part 1 (1857), p. 41, No. 29, and also Plate 14, fig. 4.

Peter B. McQuillan, Jan A. Forrest, David Keane, & Roger Grund,
Caterpillars, moths, and their plants of Southern Australia,
Butterfly Conservation South Australia Inc., Adelaide (2019), p. 127.

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(updated 10 December 2011, 30 March 2023)