My photo shows it finishing off a leaf that it began eating last night.
Instars are the different stages Monarch caterpillars pass through, shedding their skin between each stage, until they reach a maturity that allows them to form their chrysalis.
Monarch caterpillars eat only milkweed leaves. The leaves contain a white sticky sap that is a mild poison. Its bitter taste warns away many animals and insects that try to eat the plant. Certain insects however, including monarch butterfly larvae, are reasonably immune to the toxin. The clever caterpillar nips the main vein of a leaf, at the point where the leaf attaches to the stem of the plant. This drains away the majority of the toxic sap before the caterpillar feeds. As the caterpillar grows, its body accumulates the glycosides, making it unpalatable to predators. The yellow-black caterpillar colouring gives a warning to predators that the caterpillar is toxic.
Unfortunately this doesn't deter the Asian paper wasp from successfully preying on the caterpillars in New Zealand and almost wiping out many Monarch caterpillar groups.
It's about 10mm long now and, as you can see, its Monarch caterpillar colouring is becoming more prominent.
To me it looks as if all tiny caterpillar does is sit all day. Upon checking this, I found it to be correct because apparently 2nd instar caterpillars don't actually eat a lot - perhaps a leaf or two a day.
Very tiny caterpillar is growing well, too, and I'll show it to you in another post. Right now it's still so tiny that I have trouble finding it on the leaves - but it is there.
As for the two eggs?
Well they are both now quite dark, so it's anyone's guess if they'll hatch or not. I'm hoping.