Corn farmers, look to the sky at dusk and mutter thanks to the bats swooping over your moth-ridden fields: Those winged mammals put more than $1 billion back into your collective pockets, a new study suggests. The first-of-its-kind research used nets to fully enclose 20-by-20-meter fragments of large corn fields at night, thereby excluding foraging bats, throughout the growing seasons in southern Illinois in 2013 and 2014. The team’s analysis focused on damage caused by corn earworms, the crop-damaging larvae of a species of moth (Helicoverpa zea) that lives worldwide and is often preyed upon by bats such as North America’s eastern red bat (Lasiurus borealis). (The variety of corn the researchers grew wasn’t genetically modified to produce its own insecticide and thus resist those larvae. Although 84% of the corn grown in the United States does produce such insecticide, 68% of that grown worldwide does not.) Ears grown where bats couldn’t feed on moths had 56% more larvae-damaged kernels, the researchers report online today in the Proceedings of the National Academy of Sciences. On the whole, bats increased crop yield by 1.4%—a benefit that, on average and at current corn prices, adds up to a difference of about $7.88 per hectare ($3.18 per acre) and more than $1 billion worldwide. The drop in damage could be attributed to bats, the researchers say, because the crop-enclosing nets were rolled up during daylight hours to provide access for farmers and pest-eating birds. The team’s analyses didn’t estimate the value that bats provide for other crops afflicted with the same pest, including cotton and soybeans. But the findings do suggest a previously unsuspected benefit: Bat-protected ears of corn had fewer fungal infections and lower concentrations of fumonisin, a fungi-produced toxin that’s a big health hazard to livestock and greatly decreases a crop’s value.