Prickle, the bag-shelter moth caterpillar
Hello caterpillar lovers. I'm Prickle, the bag-shelter moth caterpillar. I'm called Prickle because my bristles will prickle you and give you a rash if you touch me. I am on my way to find a place to stay over winter before turning into a bag-shelter moth.
But wait, there's more
I'm not going alone on this journey. We bag-shelter moth caterpillars like company …
A lot of company!
There are 73 of my brothers and sisters setting out with me today on our great pupation adventure. You can see our trail in the photo at right. We are crossing a path to get to the grass and sandy soil on the other side, and that will lead us to our winter home among debris on the ground.
It's well into autumn, you see. We are now 4 centimetres long, so it's time for us to start the next stage to our destination of turning into bag-shelter moths in October.
Why are we called bag-shelter moth caterpillars?
We are called bag-shelter moth caterpillars because large numbers of us stay sheltered in a big silk bag at the base of a wattle or eucalyptus tree — or sometimes high up in the tree. We leave the bag to go out and feed on leaves all day (or all night), then come back to it.
If we eat all the leaves on our tree, and are not yet big enough to go to the pupation home, we all line up, single file, and head off to find another tree.
There are only 74 of us today. But we hear stories about hundreds of caterpillars sometimes forming a line. One group of 157 crossed the road at Acacia Ridge to find a new home. Unfortunately, only 141 made it to the other side.
We are determined
We cross over any terrain. We cross over prickly needles …
We cross over clumps of grass …
And we cross over sandy soils …
You can see our deep trail. When 74 caterpillars march along the same soft track, we're going to leave an impression. This indentation in the soil was nearly one centimetre deep when we had all gone though.
How do we stay together?
As we walk, we leave a trail of silk from the spinneret near our mouth. We walk head to tail following this silk thread.
Sometimes the thread gets broken, and caterpillars near the end of our convoy may get lost for a while, like the guys in the photo below.
But a couple of poo pellets from Oscar helped them get back on track.
The thread is strong
Even though the thread breaks sometimes, it is extremely strong.
The photo at left shows our trail (from bottom right to top left) nine hours after we had been through in the morning.
During the day, someone on a bicycle ran over our track, yet you can still see the silk thread (green arrow points to it) up the centre of our trail. The thread was still visible, where the afternoon sun made it sparkle, all the way to our new destination among another stand of trees.
If the weather is fine and the ground is not disturbed much, the thread may be visible for days, or even weeks.
Our old tree home
Above: Left: This is the tree the caterpillars came from. A brown stocking-like bag full of droppings and shed caterpillar skins has built up on the northern side of the tree where the parent moth first laid her eggs. Each caterpillar moults eight times until it is fully grown. Centre: The caterpillars leave strands of silk down the tree trunk that leads to their silk-bag home at the bottom of the tree. Right: The silk bag to which the caterpillars return each day or night when they have finished eating. It is difficult to see because the silk is mixed with dead leaves, twigs, and ground litter. This bag is about 30 centimetres (12 inches) wide and 40 centimetres (16 inches) long. Arrows point to entrance and exit holes in the bag.
Now that I have found my home for winter, I will make a cocoon in the ground out of my prickly hairs and spend the winter in it. In spring I will turn into a pupa, and finally emerge as a bag-shelter moth in spring (September to November).
When I am a moth, I will still have prickly hairs that will cause itchy skin eruptions and rashes if you handle me or touch my hairs.
— Prickle the processionary bag-shelter moth caterpillar