Friday, 2 June 2017

#30DaysWild Day 2 - A watched caterpillar never pupates!


A couple of weeks ago Bug Mad Girl spent the day with Nanny Moth. As usual, she came home at the end of day clutching an assortment of treasure she'd found, including a pot with nettle leaves in it. The leaves held a web full of the tiny black, spiky caterpillars of the small tortoiseshell butterfly, which she was going to look after and rear herself.

They're such gregarious caterpillars, sticking together to build a new web in the corner of their pot, moving onto the leaves to eat together and even changing all their skins together. It was easy enough to look after them at first, as they only needed a new nettle stem each day which we could get from our nettle patch in the back garden. As they grew though things started to get a bit trickier as the tiny little dots turned into eating machines, with Bug Mad Girl topping up their leaves three or four times a day. I persuaded her they may be better off on our nettle patch and we could keep a few, so we moved them down to the bottom of the garden, where they ate their way through most of our nettle patch.

After some frantic eating, our remaining caterpillars, still sticking together, decided it was time to pupate and started to wander around their pot. Eventually they stuck themselves to the lid of the pot and hung upside down like caterpillar icicles. They were finally ready to pupate.

Caterpillar icicles
They hung there for a day or two and eventually the first one pupated. We missed the big event! Then another one pupated and we missed that too! We started to wonder exactly what happened when they pupated. How did they get out of their skin and stay stuck to the lid of the pot? So, Bug Mad Girl set up a camera and decided to try and film the moment.


When they first pupate they are bright green

The bright green pupae soon turn darker
It seemed like every time she took a break from watching them, another one would pupate. There's an expression that a watched kettle never boils, well in this case, a watched caterpillar never pupates! She had to give up and go to bed and by morning only three caterpillars were left to pupate. Would she ever be able to catch the moment on film?

Only three left!
She realised that when the caterpillars were about to pupate, they uncurled slightly and looked longer and thinner. Focussing on those caterpillars and persevering, she actually managed to film the moment a caterpillar sheds it's skin and turns into a chrysalis.

video

The whole thing took about 10 minutes and started by the skin splitting just behind the caterpillar's head. Then it wriggled the skin up it's body, so it was like a bunched up sock. When the skin was up at the top of the pupa, it wriggled like mad, until the skin fell off.

Our caterpillar icicles had changed into beautiful, gold-dusted pupae.
They look a bit like bats, hanging upside sown from their lid


As for the caterpillars down on the nettle patch. We would occasionally see a few of them on the leaves and I found one that had pupated on the fence next to the nettles. I hope at least a few of the others made it and crept off somewhere a little less obvious to pupate.

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