Caterpillar Fighting

Once the graduate student in my lab told me that they have to separate the Manduca caterpillars into cups as they grow bigger, because they would fight each other to death for food if the place is too crowded. I just couldn't imagine such soft-bodied, harmless-looking creatures could be so aggressive. This week, I saw many small caterpillars in one box banging their upper bodies against each other. Some of them struggled intensely. I even saw a hornworm's little tail fell off because of the fighting. They might well be siblings so what a sibling competition. Wow! Never underestimate the aggressiveness of fragile-looking organisms.