Caffeine is a natural pesticide.

Farmers aren’t the only ones with a vested interest in keeping bugs off crops. Plants themselves have a number of defenses against their entomological enemies, including, it turns out, caffeine. The chemical serves as a natural pesticide that “disturb[s] the behavior and growth of numerous insects and their larvae,” according to a New York Timesreport on the discovery of caffeine’s natural function in 1984. (Until then, researchers had been mystified about why plants produce caffeine, as useful as it is for people.) In tests, caffeine proved effective against mosquitoes, tobacco hornworms, milkweed bugs, mealworms, and other pests; some of these tiny foes became uncoordinated, while others’ appetites were suppressed. (Aside from coffee and tea, plants that naturally include caffeine are kola, cacao, guarana, and yerba mate, among others.)

For all that, caffeine has yet to come into commercial use as an insecticide. Aside from a host of logistical issues, its effectiveness is something of a double-edged sword, as it can seep into the soil of coffee farms to such an extent that it actually harms the plants themselves. As with humans consuming caffeine, moderation is key.