Sunday, 26 July 2015

A day in the life of a pupating silk moth

It's been fascinating to watch our Chinese Oak Silk Moth caterpillars as they've pupated. The last few days before they pupate they turn in eating machines and get through a mountain of leaves. It feels like you can't give them enough leaves as they just eat everything and look big fat and 'juicy'.

When the time comes, they stop eating and start to 'wander', creeping around their cage. They climb the walls and mooch around the floor, leaving strands of silk as they go. They lose a lot of fluid and their bodies turn noticeably darker. Eventually they seem to find the perfect place to pupate and settle down to the business of spinning a cocoon.

We watched one of the caterpillars over the course of a couple of days. At 6pm on day 1, it'd finished wandering and had lost body fluid. You can see the darker patch on it's back and there are a few strands of silk on the cage.

6pm day 1
 By 8am the next morning, there was a thin layer of silk all around the caterpillar.

8am day 2
3 hours later and the caterpillar had been very busy. The layer of silk was much thicker and the caterpillar was completely surrounded.

11am day 2
By 6pm, it was starting to look like a cocoon although you could still make out the shape of the caterpillar inside.
6pm day 2
Another day and the cocoon was finished. By this point it had set hard, forming a case around the caterpillar which was now hidden away inside, safe to pupate.
6pm day 3
Bug Mad Girl did a project about silk production for homework last year, so now she wants to soak one of the cocoons after they've hatched and try and unravel it to get the silk thread. The silk trade is slightly more gruesome as they kill the pupae before unravelling the thread, so that the moths don't hatch and break the silk strand. We'll let ours hatch first! They also use different silk moths to ours, so we'll just have to wait and see whether it works.


  1. They are pretty cool - just hope they hatch out now!

  2. An excellent series of pictures. I hope we'll get to see the image.