The bionomics ofEuxesta stigmatisLoew were studied in the field and laboratory. Different features of life stages of this insect are described. Eggs were laid on the tip of corn ears inside silks, and larval development took place inside com ears. Abundance ofE. stigmatiseggs was lower in June than in other months in 1989, and higher in April than in other months in 1990. The sex ratio of adult flies on corn ears favored females, whereas the sex ratio did not vary significantly on other plant parts.