This is from a forestry website – full info and more photos can be seen there.
I thought I would
delight bore educate enlighten you with some information about the grubs I pictured yesterday: Spitfire caterpillars, larvae of our Australian native Steel Blue Sawfly (Order Hymenoptera). I’ve gathered information from Museum Victoria, Wikipedia, CSIRO, a Forestry site, and a South Australian Government website.
The sawfly is a wasp, related to the Cherry and Pear Slug. It has a stocky body, usually a dark metallic blue, and does not sting. It has a double pair of wings with a span of about four centimetres. The adults are rarely seen, and spend their time hanging around their host tree. The sawfly gets its name from the saw-like ovipositor of the female. She opens holes in the underside of the leaf and lays her eggs.
The Spitfire larvae, about 8 centimetres long, love their tucker. Mainly active around late winter and spring, they sprawl around enmasse during the day, but at night they disport around the tree chomping gum leaves. They can gather into groups of as many as two hundred.When threatened, they raise their heads and exude a yellow-green liquid, strongly flavoured by eucalyptus oil extracted from the gum leaves.
Crossing Concrete at Brisbane 2012: By Tzedragon (Captured on iPhone) [GFDL or CC-BY-SA-3.0], via Wikimedia Commons
They did this to me, the other day. About ten of them all jerked their heads up at the same instant. Needless to say, I leapt back and didn’t bother them again. I have no idea if they do actually do
spit the stuff, and I didn’t want to take the risk of anything nasty dropping in my face.
Eventually, about mid spring, the larvae are ready to pupate. Still enmasse, they make their way into the ground, burrow in several centimetres, and make themselves a strong paper-like cocoon. It might take two or three years before the adult emerges.
I intended to take fresh photos today, but the bunch had moved up the branch overnight (featured photo). I think they are fascinating, and it will be interesting to see if they do survive to pupate. Small groups of twenty or so do not always survive. A few birds, currawongs and cuckoo-shrikes will eat them. Good luck to them!
By D. Gordon E. Robertson (Own work) [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons