During a recent trip to Borneo, I participated in an inventory of frogs in rainforest streams. When searching for frogs along streams of Borneo, usually something really interesting shows up on the banks of the stream. This time we found something even more interesting than usual, a thing I have never seen before despite numerous visits to this area.
It was a white, quite unstructured “thing”, suspended in silk threads inside a cage like structure. None of the participants in the inventory, including several field assitants that had worked in this part of Borneo for many years had ever seen anything like this. I had no idea what it could be and posted the picture on several web sites, hoping that someone would recognise the structure.
The power of internet is amazing. In just a day several of my colleagues had solved the problem. It turns out that this is the pupa of a certain butterfly. The butterfly is very hairy as a caterpillar.
Apparently, the caterpillar use its hairs to create the cage in which the butterfly hangs suspended during its pupa stage. One can only guess why this intricate behaviour has evolved, but a fair guess is that it in some way protects the pupa from predators or parasites.