We examined food habits of Brazilian free-tailed bats (Tadarida brasiliensis) at 3 colonies in central Texas over 3 summers. Fecal samples collected from 1,550 bats contained remains of 12 orders and 35 families of insects, documenting the most diverse diet ever reported in insect-eating bats. Daily and seasonal patterns of insect consumption were similar at the 3 sites and closely correlated to patterns of emergence, migration, and availability of adult populations of corn earworms Helicoverpa zea and fall armyworms Spodoptera frugiperda, both species of noctuid moths and major crop pests. The percentage of feces volume comprised by moth remains increased from 14.8% ± 2.1 SE (range: 6.3–43.7%) to 43.0% ± 7.1 (range: 1.7–73.5%) in samples collected at midnight versus dawn on days when large influxes of migratory moths arrived in Texas in early morning, following their massive emergence from northern Mexico. Daily patterns diminished later in the season, after moth populations became established in local crops and were available in large numbers throughout night. Moth consumption decreased in both evening and dawn feeding periods when crops senesced and moth populations declined. These and other data suggest that crop pests comprise a substantial portion of the bats' diet and that bats provide valuable natural pest control services.