May 2018

Follow the Leader!

I found these caterpillars walking in a chain down the driveway in our rural property in the Gold Coast Hinterland. They were all heading in the same direction. I have lived here for 16 years and have never come across this before. What are they?



A female Coastal Bag-shelter Moth, Ochrogaster luniferEgg mass with newly hatched Caterpillars A mass of nearly fully grown processionary caterpillars You have found Processionary Caterpillars, sometimes called ‘itchy grubs’ which are the larvae of the Bag Shelter Moth, Ochrogaster lunifer. These hairy caterpillars produce long head-to-tail processions commonly seen traversing across the ground in late summer and during autumn. 
 Found commonly throughout Australia, females of the Coastal Bag-shelter Moth lay their eggs on a variety of host plants but mostly on wattle and beefwood. After hatching, the caterpillars form a communal silken shelter at the base of the tree. Copious amounts of leaves are eaten by the caterpillars and sometimes they can defoliate the whole tree. If this happens and the caterpillars have not reached maturity, they will leave the tree and travel across the ground in a long single-file procession, resembling a miniature freight train, looking for another food tree to devour.
The caterpillars are fully grown in May and are ready to leave the wattle tree. They crawl away from the tree in a long procession that may break up into groups of ten or less caterpillars. Some travel up to 150 metres from the tree before they burrow into the ground. Each caterpillar forms a chamber of soil and silk incorporating their long irritating hairs. The caterpillar sits out the winter within the cocoon and does not turn into a pupa until the spring in September. The adult moths emerge in late October, all those within an area emerging within a few days of each other. They have no mouth parts so cannot feed and consequently die within a few days.
The furry processionary caterpillars have a notorious reputation for causing irritating rashes. If a caterpillar comes into contact with the skin an intensely itchy dermatitis can develop. The caterpillars are completely covered with numerous long, thin hairs and are very brittle so they must never be handled. The coarse hairs easily penetrate skin and break off, and are difficult to remove thanks to hundreds of microscopic barbs. The hairs contain an irritating protein that produces an allergic response in humans and other animals. Eye injuries, occasionally blindness, may also result from the penetration of caterpillar hairs. 

Click here for more information (283 KB) pdf document icon

Queensland Museum's Find out about... is proudly supported by the Thyne Reid Foundation and the Tim Fairfax Family Foundation.