Ewepe © Mike Gillam
By MIKE GILLAM
April 2020 was unseasonally hot; on a few days five deg. C above the average maximum for the month. So I delayed this piece but a week is a long time given the vagaries of Centralia’s climate and the daily rhythms of its inhabitants. Suddenly we had the mid week cold snap so it’s past time to publish the image of processionary caterpillars and once again I’m playing catch up.
Processionary caterpillars are known by Arrernte people as ewepe, a sensibly short name that doesn’t try to match the collective length of the organism. I hesitate to use the latin name because the bag shelter moth caterpillars are certainly composite, meaning more than one species are likely to occur in Centralia.
April is the month we expect to see the lines of shuffling caterpillars, conspicuous and rope like, seemingly oblivious to hazards or predators. Doubtless somewhere around town the ewepe are already marching to announce the beginning of winter. We’ve seen none at the time of writing in Hele Crescent, where Acacias are bountiful.
On their walkabout the ewepe leave a silken thread for their tribe to follow and there’s little point in trying to determine why some choose to lead and most to follow. If one caterpillar measures 4cm. a conga line of 150 will stretch across the regulation width of a commercial driveway. Over the decades I’ve seen such a line, sometimes longer and frequently shorter.
One Autumn morning, our concreter arriving early to tweak the formwork before pouring the driveway, earned significant brownie points when he stopped his truck to wait for the caterpillar trail to pass. An hour or two later I took a series of photographs that reminded me of a cloud drifting over a mountain. The image really spoke to me when I converted it to black and white.
Over the decades I’ve paid my dues many times crawling around on hands and knees following ewepe trails patiently waiting for them to cross a photogenic patch of terrain. No matter how careful I always pay the “itchy grub” price, lumps and welts that last for several days.
Ewepe are incredibly simple and instinctive beings. They have no road sense or discernible fear so it’s not uncommon to see a trail brutally smashed into thirds by the wheels of a vehicle. The resulting carnage and confusion causes them to mill around and prolong their exposure to danger.
Those of empathetic nature who encounter such a situation are advised to gently sweep the caterpillars into the gutter using a branch of soft leaves. A leaf blower would be perfect!
Not wishing to offend any safety officials reading this column I hasten to add; children should not be on the road so leave it to your parents. Please make sure you’re perfectly safe, look for traffic and retreat to avoid being squashed; preferably wear a high viz vest and maybe have a warden with a stop sign to watch your back. You could also file a traffic action plan with the appropriate authorities. After all we’re much smarter than caterpillars!
From an early age Centralia’s children are enchanted by the appearance of processionary caterpillars in the Autumn. Predictably adults show them how to join up the lead with the tail, resulting in an aimless circle that amuses onlookers for a moment. Restoring the purpose of the foraging line can result in confusion. New leaders can be as hesitant and beholden to the deficit of the group as politicians leading a country.
My knowledge of ewepe’s life-cycle is unfortunately patchy and I’ve not had the opportunity to consult with locals so here goes. I’ve noticed moths in October and November and small caterpillars on Acacias in January so eggs are laid sometime in between and the moths have a very short lifespan.
The early larval stages are difficult to find but they appear to feed as a group and grow slowly in comparison to others such as hawkmoth caterpillars. As the caterpillar grows it must shed its skin and each of these stages, perhaps five or more, are called instars.
It seems likely that ewepe take periodic ‘rests’ especially in response to inclement weather (high daily temperatures or rain), when they often form campsites at the base of edible shrubs. Diurnal movements reach a hiatus in the mild days of Autumn. By now the growing ewepe must move more frequently as they strip shrubs, the caterpillars striving to increase body weight and fat in preparation for winter.
After a few weeks they climb a suitable tree or tall shrub, mostly Acacias such as ironwood, prickly wattle and witchetty or the beefwood, Grevillea striata where they build a remarkable silken nest in the upper branches.
Another distinctive species builds a canopy nest in Eremophila longifolia, which is also the favoured food plant of the sacred hawkmoth caterpillar Utnerrengatye.
It seems probable the final stage instars begin to pupate quite soon thereafter and overwinter in this state. Field studies from Queensland record pupation occurring in a ground ‘nest’. This would explain the prevalence of nests around the base of food plants but why do they bother expending all that energy building an elaborate nest in the canopy for short term occupation?
Whatever the case the warmth of summer is a likely trigger for the pupa to emerge as moths, leaving the nest site to breed and lay eggs. I photographed fully formed pupa on 28 September 2014 and on that occasion the adult moths departed one month later on about 22 October.
Expanding on these facts would not be difficult, a re-sealable slit in an easily accessible ground nest or canopy bag would allow observation throughout the winter and spring. Alas another project on my long list of gonnas. Better still, maybe someone else has already done this!
With trademark ingenuity, Australia’s Indigenous peoples harvested silken scarves from the nests and after thoroughly washing them in water used these as bandages to wrap and cover wounds. I daresay a residual itch might be quite effective in taking the patient’s mind off a spear gash or broken bone!
I hasten to add that this process of handling nest silk would require significant patience and skill. It’s not recommended unless you have access to the full pandemic kit of disposable scrubs, gloves and face mask. Failure to treat ewepe with the greatest respect will result in persistent itching or worse. Asthmatics and children are especially vulnerable and may need urgent medical treatment.
This reaction to the caterpillars is celebrated at one sacred site I was shown, an unusual rock formation studded in raised rounded boulders and exposed rocks. The name for this place translated from Arrernte, “itchy stomach”. In both directions the gently undulating range evokes the flowing movement of the ancestral ewepe during the time of creation.
If the ewepe tribe do grace your garden with a visit you must be doing something right; rest assured their appearance is not a natural disaster of biblical proportions. Please do not reach for a spray can or the vacuum cleaner (true story, some-one actually did this!). Enjoy the opportunity to share this enchanting event with your kids from a safe distance. If the caterpillars strip every leaf from a prized plant, relax in the knowledge they will move on and the plant will soon freshen up with new growth.
Note: After writing this piece I discovered a post from the kangaroo sanctuary south of Alice Springs. On 16 April this year they observed a caterpillar line estimated to be seven metres long. It looks like I’m at least two weeks behind the times!