Seen through windscreen, curious growths, tarry sheaths round small tree boles on the scratty avenue of young gums, in the late afternoon. Out we grunt under our own steam to examine one.
But, oh, it's a close-knit weave of finger-long blue-black bodies plastered in oval shiltron, certainly more cunningly ordered than gummy worms in a lolly* jar tapering to tubular yellow tails, rippling a gut-wrenching warning as hand approaches. Mexican wave? No. Opening alien maw, eagerly fringed with ghastly, flexing mandibles.
Never were Myrmidon hoplites so cleverly arrayed, neither Dane nor Anglo-Saxon held better shield wall, no Switzer pikemen responded so adroitly as these critters bristle nightmare's ramparts.
Phil swerved tractor round parked car and stopped to see what we were about. 'Spitfire caterpillars, is it? I should spray 'em. Don't go too near. You've had enough bites as it is, lately.' He grinned at me and juddered off.
The circling tail formations, rimmed with heads and thick legs clinging to bark, were studded too, throughout, with blue-black button heads, it seemed sardined against the racks of tails, these spitfire sawfly grubs wielding the very tree they desecrate:
yellow brown goo, eucalyptus oily, oozed from gaping mouthparts, chemical triumph over hungry birds, (though ants will take them nonetheless).
I went out to experiment, wondering whether the tails could dribble too, since tails or bums*, as you will, it was which dramatized their ranks.
The squadrons were sleepy at the noon, they liven up near nightfall when they separate and pillage leaf by leaf.
Tails hardly raised though I stroked and prodded them with proffered card but only mouths would lazily taint.
It seemed they have the birds well drilled and can sleepily trust in their self-restraint.
So now some science has usurped first yuck; and yet I replay the waving alien maw, that gut-churning synchrony (detonates more shock and awe than any goose-stepped spring missile-trundling) wielding that most primal weapon of disgust, delirium's very crenelation, against the nerve of avian deprecation.
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These are Spitfire Sawfly larvae not caterpillars and have six strong stump legs. The sawfly is in fact a wasp relative. The larvae wave their tails in communication and deterrence, en mass in preference, and their mouths exude a sticky yellow substance which is mostly eucalyptus oil which disgusts birds. (It would be harmful in eyes of course.) They congregate for defense and sleep in the day and disperse at night to eat up the leaves of gum tree they have chosen. They will often strip a small tree completely. For this reason they are regarded and treated as pests.
*Aus calls 'lollies' what UK calls 'sweets' and US calls 'candy'.
*Bums - as in bottom, arse or ass.
About damage caused by and control of Spitfire Larvae Wikki has this:
Larvae of spitfires feed on the foliage of young trees and regrowth stems, and can strip the branches of foliage particularly at the tops. This is usually replaced during the spring-summer flush of leaf growth. Serious retardation of high growth may result from repeated attack but death is unusual. Wandoo (a eucalypt) is the most commonly attacked species in Western Australia.
Where the clusters of larvae are accessible the simplest method of control is to remove and destroy them during the day. There are a number of parasitic wasps which also have some controlling effect and widespread damage by this defoliator is rare.
