Black Slug Moth
(one synonym : Doratiophora acasta Froggatt, 1907)
Stella Crossley & Ian Baird
(Photo: courtesy of Geoff Byrne, Kununurra, Western Australia)
When these caterpillars hatch, they feed communally. They sit on the leaf surface, touching each other, eating initially only the surface layer from the leaf.
Later instars separate, and get a whole leaf each. The caterpillars have been found feeding on the foliage of various trees in MYRTACEAE, including:
as well as on
The caterpillar is black, sometimes grey in the middle, with very pale green fleshy spikes along the back, and cream fleshy spikes along the sides of the caterpillar. Four of the spikes on the thorax protrude rosettes of cream stinging hairs if the caterpillar is disturbed. The contrasting coloration of the caterpillars offers a warning that these caterpillars sting. The head is brown, and normally tucked under the body. The caterpillars move like slugs because their legs are reduced.
The caterpillars are known sometimes to totally defoliate a tree, and are then considered to be a pest. However the caterpillars have many predators and parasites, which normally keep the population at tolerable levels.
The caterpillars grow to length of about 2 cms. When fully grown, the caterpillars leave the foodplant and walk as far as 20 metres looking for a suitable crevice or piece of leaf litter in which to pupate.
The caterpillars pupate by rolling into ball with the underside outside, then encasing this in silk, and dousing this with a liquid that sets hard. Thus the pupa ends up being enclosed in a spherical brown woody cocoon, about 0.7 cm in diameter. The pupal period varies from 2 to 10 months.
The adults have brown wings, with a row of four black dots each outlined in orange on each forewing. The moths have a wingspan of about 4 cms. They often sit with the forewings vertical, and the hind wings held horizontally, like skipper butterflies.
The eggs are white and spherical. They are laid in an irregular mass, and covered by the female moth in brown hair.
The species occurs in:
The adults may easily be confused with those of of Doratifera quadriguttata, but the adults of Doratifera casta are darker and the black spots are more distinct. This is one case where the caterpillars provide much clearer identification of the species.
Further reading :
John L. Capinera (Ed.),
Encyclopedia of Entomology,
Springer Science & Business Media (2008), p. 1734.
Ian F.B. Common,
Moths of Australia,
Melbourne University Press, 1990, figs. 29.1, 52.13, p. 302.
James T. Costa,
The Other Insect Societies,
Harvard University Press (2006), pp. 577.
Phillip W. Hadlington & Judith A. Johnston,
An Introduction to Australian Insects,
UNSW Press (1998), p. 64.
Harriet, Helena, and Alexander W. Scott,
Australian Lepidoptera and their Transformations,
Volume 1 (1864), pp. 18-19, and also Plate 6, top right.
(updated 29 January 2013, 17 February 2017, 24 April 2019)