Ochrogaster lunifer

(Photo: courtesy of Cathy Mardell, Port Macquarie)

Ochrogaster lunifer (Herrich-Schaffer, [1855])
(one synonym : Teara contraria)
Processionary Caterpillar
THAUMETOPOEINAE , NOTODONTIDAE

Don Herbison-Evans ( donherbisonevans@yahoo.com )
&
Stella Crossley

Ochrogaster lunifer

These Caterpillars are grey and hairy with a brown head. They are famous for walking in processions. Their hairs are thought to cause skin rash ( urticaria ) in sensitive people, although it has been asserted that it is the hairs on the dead larval skins and adult moths that cause these problems. The rash can last for months after the exposure, and easily become infected. Not only do humans suffer from irritation from the hairs. The hairs have also been implicated in causing abortions in horses, by puncturing the intestinal walls allowing infection by pathogenic bacteria.

When disturbed, the Caterpillars are inclined to curl up into a tight hairy spiral. The Caterpillars feed nocturnally on a variety of Australian native trees and shrubs, including the Wattles ( MIMOSACEAE ) :

Raspberry Jam Wattle ( Acacia acuminata ),

Hickory Wattle ( Acacia aulacocarpa ),

Black Wattle ( Acacia concurrens ),

Lightwood Wattle ( Acacia implexa ), and

Sydney Wattle ( Acacia longifolia ),

as well as

White Box ( Eucalyptus albens, MYRTACEAE ),

Red Maple ( Acer rubrum, SAPINDACEAE ), and

Beefwood ( Grevillea striata, PROTEACEAE ).

nest high in a Gum tree
(Photo: courtesy of Deborah Keogh, Scone, New South Wales)

During the daytime, the Caterpillars hide communally in a nest, a shelter of silk, frass, old skins, and other debris. Sometimes this is located on a shoot at the end of a branch, or sometimes high on the trunk.

nest at base of a food plant, opened to show the caterpillars inside
(Photo: courtesy of Andrew Sharrock, Maclean, New South Wales)

Sometimes this is located on the ground at the base of the foodplant. The different nesting habits are evidence that there may be two or more species currently being included under this name. The hairs from old skins in such a nest can get blown around and spread over adjacent vegetation, which is of concern for humans and animals in the area.

The presence of the nests of these caterpillars on properties with breeding horses has been associated with spontaneous abortions in these horses. The case is not proven, and mechanisms for such a cause and effect are unclear. The only reasonable suggestion so far has been that possibly the hairs carry pathogenic bacteria, whose infection causes the abortions. Much work needs to be done to investigate this properly.

(Photo: courtesy of Bryce Burrows)

When mature, the caterpillars go walkabout to find somewhere to pupate, having grown to a length of about 4 cms. The Caterpillars also go walkabout if they totally defoliate their food tree and have to locate another one. Each Caterpillar when it walks, leaves a trail of silk from its spinneret near its mouth. When a Caterpillar of this species encounters such a silken trail, it starts to follow it.

silk 'rope' of threads laid by the train of caterpillars ascending and descending the trunk every night
(Photo: courtesy of Judy Ormond and Lyn Loger, Nathalia Wildflower Group Inc)

Thus the Caterpillars when they walk are inclined to follow each other, nose to tail, like a minature freight train. Cathy Mardell of Port Macquarie reported counting 203 in one such procession.

cocoon opened to show the pupa inside
(Photo: courtesy of the Macleay Museum, University of Sydney)

They pupate in a silk cocoon in ground debris.

The adult moth have a wingspan of about 4 cms. They have forewings that are dark grey or brown, and hindwings that are white shading to grey at the base. Some have a pale dot in the centre of each forewing. The moths have a yellow banded abdomen which ends in a white tuft of hairs. These and the hairs on their feet can cause Urticaria. It is unwise to handle the moths directly.

acting dead: display posture
(Photo: courtesy of John Moore, Ravenshoe, Queensland)

When disturbed, the moths are inclined to lie still on one side with a curled abdomen, so appearing dead.

Some have white lines across the wings. Again, the variety of colour forms suggests that there may be more than one species present in Australia.

pale brown form
(Specimen: courtesy of the Macleay Museum, University of Sydney)

Female adult moths lay several hundred eggs, and lay their eggs in one mass on a food tree. They cover them with a layer of hairs from their tail. The female moths have no mouthparts and so die after a few days.

female
(Specimen: courtesy of the Macleay Museum, University of Sydney)

Specimens have been obtained from every mainland state and territory in Australia, including:

Victoria, and

(Photo: courtesy of Jim Foster, taken at Malanda, Queensland)

Further reading :

Densey Clyne,
The Best of Wildlife in the Suburbs, Oxford University Press Australia 1993, pp. 133-135.

Graham J. Floater and Myron P. Zalucki,
Habitat structure and egg distributions in the processionary caterpillar Ochrogaster lunifer: lessons for conservation and pest management, Journal of Applied Ecology, Volume 37 (2000), pp. 87-99.

Graham J. Floater,
Estimating movements of the processionary caterpillar Ochrogaster lunifer Herrich-Schaffer (Lepidoptera: Thaumetopoeidae) between discrete resource patches. Australian Journal of Entomology, Volume 35 (1996), pp. 279-283.

Graham J. Floater & Myron P. Zalucki,
Life tables of the processionary caterpillar Ochrogaster lunifer Herrich-Schäffer (Lepidoptera: Thaumetopoeidae) at local and regional scales. Australian Journal of Entomology, Volume 38, Number 4 (1999), pp. 330-339.

Peter Marriott,
Moths of Victoria: Vol 2: Noctuoidea(A),
Entomological Society of Victoria, 2009, pp. 8-11.

J.J. Van Schagen, J.D. Majer, and R.J. Hobbs,
Biology of Ochrogaster lunifer Herrich-Schaeffer (Lepidoptera: Thaumetoedae), a defoliator of Acacia acuminata Bentham, in the Western Australian wheatbelt, Australian Entomological Magazine, Volume 19, Number 1 (1992), pp. 19-24.

J.J. van Schagen, R.J. Hobbs, and J.D. Majer,
Defoliation of trees in roadside corridors and remnant vegetation in the Western Australian wheatbelt, Journal of the Royal Society of Western Australia, Volume 75 (1992), pp. 75-81.

Paul Zborowski and Ted Edwards,
A Guide to Australian Moths, CSIRO Publishing, 2007, pp. 174, 177.