text: That depends entirely on what species of catterpillar and what quantity of caffeine.\n\nCaffeine is a widely occuring substance found in numerous unrelated plants. All of those plants are fed on by different species of catterpillar and the caffeine has no effect at all.\n\nHowever if a caterpillar that doesn't normally feed on caffeine producing plants is exposed to caffeine it could die. Or it could be rendered sterile. Or it cold fail to pupate. Or it could start behaving oddly such as climbing down off the plant and wandering across the ground. The effects vary widely with the species of catterpillar and the dose of caffeine.