My Itchy Fingers

A Peep into the Changing Room

As we grow bigger, taller or even fatter, we will need to discard our old clothings that do not fit us any more for bigger ones. Similarly, as arthropods (eg insects, arachnids, crustaceans) grow, they need to change their ‘clothing’ – a process called Moulting (or Molting), where old skin that has grown tight are shed for new one. Insects have an exoskeleton (i.e., they have their skeleton on the outside), making it a problem for a growing insect as the exoskeleton is rigid and cannot grow or stretch like skin. To make room for growth, the exoskeleton has to be discarded periodically. They shed their old, small exoskeleton after they grow a new and bigger one that is not yet hardened. This new exoskeleton gradually hardens and no growth is possible until the arthropod  moults again. Moulting cycles run nearly continuously until the animal reaches its full size.

Itchyfingers were lucky to have witnessed, or rather, peeped into part of this private moment of a tiny grasshopper changing into its new look. 🙂

This grasshopper was almost done with his skin shedding when we found
him. “When a nymph is ready to moult, it climbs onto a leaf or a branch.
It may even hang upside down. Slowly, the nymph slides out of its old exoskeleton.
Underneath, the nymph has a new, soft exoskeleton. The nymph puffs up with air.
This makes its body bigger while the new exoskeleton hardens.”

Did you notice that the body size is much bigger than the old skin, or moult? Did you also notice something missing?

Our friend was missing one leg!

Many arthropods are able to lose part of their limbs when they were caught by predators to make time for escape. They are able to regenerate lost body parts and their innervation (the distribution of nerves to a part). However, the regenerated limb would probably be unsegmented and remained much shorter than the intact leg parts. Also they would not be able to regenerate their limb if they have gone through the last moult of their lifespan.

This grasshopper was about an inch long, and since Itchyfingers are no grasshopper expert, we weren’t sure if this one is a fully-growth adult that has missed its last chance for regenerating new limb. 😮

A look at the moult, which is the exact replicate of the grasshopper. Even the
antennae could be clearly seen! Notice the white thread-like tubes? On Francis
Seow-Choen’s A Guide to the Stick and Leaf Insects of Singapore, there is a
picture of a Stick Insect moulting. There, the Stick Insect hangs from its
abdomen still attached to its moult, with two white thread-like breathing tubes
joining the old skin to the moulting insect. See this excellent series of Stick
Insect moulting pictures at this site. So I suspect the white substance shown
here could be the breathing tubes or thoracic air sacs…Do correct me if I’m wrong! 🙂

During moulting, the insect will swell up its body by taking a large quantity of
water or air, thus splitting the old exoskeleton from the top into halves to
allow the insect to slowly make its way out. This could take several minutes.
The new exoskeleton is so soft that the insect cannot support itself and find
it very hard to move. It has to continue pumping itself up to stretch the new
cuticle and harden it. We could tell it was pumping up its abdomen as it was
constantly stretching itself out…

The moult was dropped onto the leaf a few centimetres away from the grasshopper. I read that some insects eat their own moult for the protein because in the initial phase of moulting, the insect has to stop feeding before releasing a mixture of enzymes that digest the endocuticle (the inner, elastic layer of an insect cuticle) and thus detach the old cuticle. Hence this old cuticle provides a ready food source for the insect to regain its strength. Being Itchyfingers, I tried to put the discarded skin back to the same piece of the leaf where the grasshopper was to see if it would eat it… :p

We were expecting him to move over and eat the moult after he had pumped
and hardened up enough. But while waiting, we were constantly distracted by
the nearby nesting birds and  each time we looked back, the moult was further
away and eventually dropped onto another piece of leaf before falling onto
the ground…We won’t sure if it was the work of the strong wind or could it be
the grasshopper had kicked it away as it didn’t want to attract attention
from predator since he was at his most vulnerable stage, especially when
he had only one leg? The translucent shell was so glaring as compared to the
well-camouflaged insect, so it might be a good idea to keep it away…

The grasshopper stayed at the same position until we left for the day.

The following week when we visited again, we were surprised to see this guy at the same spot again. Well, it seemed like the same insect, cos it also had only one leg…

He had grown visibly bigger and was munching on a leaf…

The grasshopper positions itself so that it is able to eat the leaves of the
plant by means of a circular to and fro motion, with extension and flexion
of the head. The mandibles chew and swallow the bitten-off leaf portion in this
semi-circular motion. When it reaches the end of the leaf, it goes back to the
starting position and repeats its feeding pattern, leaving characteristic large
rounded bite marks on the leaf

Also see related posts:
> Dun Pray Pray
> Eating Its Own Kind? – Spidey Galore #2
> Jaws – Spidey Galore #1
> ‘Leaf’ Me Alone
> Masters of Disguise and Camouflage
> A Visit to the Hospital
> Attaining Immortality – Body Preservation