Today’s Discovery – Shake it, pupa, shake it!

I like to make discoveries – making an observation and figuring out something I didn’t know before. Quite often, this happens in our Ecogarden. Like today, when I checked on the Atlas Moth pupae that have caused quite a stir among some of our staff here at the Science Centre.

Cocoon in Bird Nest Fern
There are about a dozen of these things in that one fern near the Camphor tree

All those remaining caterpillars still roaming around the almost bald Camphor tree the last time I visited had obviously moved to the neighbouring Bird Nest Fern to find a suitable support to pupate on.

Lifting one of those big fern leaves to examine the cocoons attached to it, I noticed a rhythmic knocking in the leaf. At first, I thought the leaf was rubbing against another leaf, or the wind blowing across it caused it to vibrate. But the knocking was too distinct, and I started to suspect that it came from the cocoons.

Some further experimentation – lifting other leaves without cocoons, lifting other leaves with cocoons, turning the same leaf at different angles – soon confirmed: the pupae were shaking inside their cocoons!

Cocoons in Bird Nest Fern
Notice the bare Camphor tree in the background...

Whenever the angle of a cocoon was changed significantly – eg by me turning a leaf to look at the cocoon on its underside – the pupa inside must have twisted back and forth or knocked on the walls of its enclosure some other way. All I know is I could feel the knocks in the leaf, something that might be startling enough to deter a would-be predator, I guess.

Once I had confirmed that to myself, I didn’t touch the fern any more – we don’t want to stress our metamorphosising friends too much!

4 responses to Today’s Discovery – Shake it, pupa, shake it!

  1. Kiat Teng says:

    Interesting discovery, Andy!

    But I suspect that more might be going to shake them after reading this. 🙂


      • Kiat Teng says:

        Not advisable, Danny. I just learnt from someone else’s experience that if shaken too much, there might be liquid oozing out, and that the pupa will break out of the cocoon and die…


      • Andy Giger says:

        Indeed, it isn’t a good idea to shake the pupae!

        I didn’t shake them, anyway – I just gently turned them to have a look. Then they shook themselves inside their cocoons!

        But triggering that too often is probably not too good for them either, so it’s best to let them rest…


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