This is the picture I posted about two weeks ago of the Monarch butterfly caterpillar just after it had hatched eating its egg.
Here the caterpillar is only 3mm long, but it started eating right away. At 48 hrs old it had grown to 6mm long.
It does not have the bright colors yet to warn predators that it will taste terrible as it starts to eat the milkweed plants that are its food.
Here the caterpillar is 10 days old and 25mm long. It had just shed its skin and was ready for a growth spurt. Notice how big the head is compared to its body size. The head does not grow in between skin sheds, but the rest of the body does.
This picture was 48 hours after the one above and it is now 45mm long. It ate a lot in two days and became quite fat. Notice how much smaller the head is now than the body.
At this point it is full grown as a caterpillar, and starts wandering for a safe place to change into a chrysalis.