Monarch caterpillars get more aggressive when they are hungry, resulting in them headbutting and lunging at other caterpillars in an attempt to secure food
Source:
https://www.newscientist.com/article/2260172-very-hangry-caterpillars-could-help-reveal-genetic-basis-of-aggression/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home