Newborn didn't eat

[David Calhoun]

I brought inside a milkweed leaf with an egg on it and put him in a plastic cup.After hatching, instead of eating
like he was supposed to , I found him, standing on his hind legs with his body extended straight out ,
from the side of the cup.I coaxed him back on to the leaf,closed the cup, checked a few hours later, and he was on the plastic again. Also,I noticed he used the "inchworm" method of walking. He later died. I had checked the egg when I brought it in-it looked like a classic monarch egg to me.What accounted for this behavior?-Was it anything that I did?

[Mona Miller]

I've had them wonder off the leaf, put them back, wander off--toddler behavior. Sometimes they make it and sometimes they don't.

[flgflowers]

I've never seen a Monarch caterpillar walk like an inchworm. Are you sure it was a Monrch
Caterpillar? Maybe it was another caterpillar that just happened to get on a milkweed plant.

[Mona Miller]

I have seen them rear up on their hind legs, but never an inch worm gate.

http://www.monarchwatch.org/biology/index.htm
Biology of the whole cycle.

[vigilante]

Larva of Hover Fly extends and inch-worms as you described; the green larva species.
Both it and the brown larva species eat the aphids.