A study was conducted in the Lower Rio Grande Valley of Texas from 1969–73 to help define bollwormH. zea(Boddie) and tobacco budwormH. virescens(F.) population dynamics. A total of 39,277 eggs and 23,396 larvae of Lepidoptera was collected from 95,241 individual plants of weed species and 12,780 row ft of cultivated crops. Budworms peaked in March and constituted over 85% of theHeliothiscollected from July through October. Both species ofHeliothispeaked on tomatoes about mid-April and heavy infestations of budworms occurred again in August. Bollworms peaked in June on cotton whereas budworms increased tremendously the last half of July and remained at high levels during August. Budworms were found on more species of plants than bollworms.