From the 3rd – 8th instar, caterpillars bear urticating setae (microscopic barbed hairs) on their abdominal segments producing more at each moult.

The final 8th instar caterpillar carries more than two million setae[4] which cause skin irritations and rashes in humans and other mammals.

[5] In April to May (Autumn), the 8th instar caterpillars leave the nest permanently in search for a pupation site where they over-winter underground as a pre-pupa.

[6] The caterpillar over-winters underground from May to October, then spins a cocoon and forms a puparium between September and November (Spring).

[2] During the day the caterpillars shelter communally in a bag nest made of silk, excrement, shed skins, and other debris.

When mature, the caterpillars seek out a place somewhere distant from their food plant to pupate, again leaving a silk trail as they walk.

The egg masses, larvae (caterpillars), and adults of O. lunifer all have urticating scales or hairs that are harmful to humans and other animals.

Records of Bag-shelter nests and caterpillars causing adverse effects on the health of humans and livestock date back to the early 1900s [8] (as Teara contraria)].

Ochrogaster lunifer caterpillars are covered in harmful tiny hairs called true setae, and these cause an irritating dermatitis upon contact with human skin.

[10] In horses, ingesting O. lunifer caterpillars may cause abortions, a condition in pregnant mares called equine amnionitis and foetal loss (EAFL).