Monarch attack!

It's been something of a dramatic day in the monarch nursery! This morning I was really worried about the two 7 day olds. They were very listless and wanted nothing to do with their food. When I tried to offer a fresh leaf, they reared back and shook the upper potions of their body with violence. A few hours later I found two discarded head capsules and the remnants of a skin - another molt. I've completely lost track of the instars at this point.

Head capsule

Shed skin - they didn't seem interested in eating it this time.

This afternoon the real drama began. While feeding the larger 9 day old, I glanced over at the 7 day olds. One of them (slightly larger than the other) was violently thrashing his head against the other! I quickly grabbed a leaf to shield the small cat from his attacker. Luckily the little one crawled away without any apparent damage done. I've now separated the two into different dishes and with different leaves. I had heard of aggression between larger and smaller instars when food seems scarce, but I didn't expect it from two hatchlings with only a few hours age difference. I have trouble telling the two apart, they are so similar in size. I suppose the attack was a result of the single leaf that I gave them at any one time...

I think the 9 day old is about to molt - perhaps for the last time prior to pupation. When I offered him fresh food, he threw back his head and thrashed just like the smaller cats did earlier today. The difference was that when this cat thrashed, I could actually hear the snapping sound when he bumped the side of the container. I wonder if anyone has ever succumbed to a caterpillar bite? After what happened earlier, I wouldn't be surprised.

I snapped a few pics for size comparison: