Lonely caterpillars barf at their enemies for protection

A lone caterpillar is more likely to vomit when it encounters another critter than one hanging out with its posse. According to a new study, lonesome caterpillars barf up a pea-green mash of half-digested plants to defend themselves against predators. Although caterpillars regurgitate digestive juices in groups too, it seems they don't feel the need to do it so often since the group offers a bit of protection - or maybe they're just more polite than we think.

But caterpillars don't have a monopoly on strange defense behaviors. Malaysian exploding ants internally combust and hagfish ooze a gooey slime, to name a few.