Tiny caterpillar is now about 3mm long. It's an active caterpillar and moves well, around the leaves, and I often have to search to see where it has got to. As you can see, it has eaten a lot of the leaf that its on. I'm fascinated because, even if it goes off this leaf, it later goes back to it and carries on eating where it left off.
In the picture below, look above the caterpillar and you will see a hole it ate when it was really tiny. Notice how the eaten section hasn't gone right through the depth of the leaf, but rather it has just eaten around the veins.
I'm guessing that its tiny, immature, mouth can't yet cope with nipping the back of the leaf vein to drain out the toxins in the white 'milk', so it has eaten around the veins to avoid the toxins that way.