Development of immature Mexican corn rootworm, Diabrotica virgifera zeae Krysan & Smith, was investigated at 8 temperatures ranging from 15 to 33°C. Development to adult was only completed in the range from 15 to 30°C; larvae failed to complete the 3rd instar at 31.5 and 33°C. Development from hatch to adult emergence was fastest at 30°C (≈25 d), and slowest at 15°C (≈105 d). Developmental times, from hatch to adult emergence, differed for males and females, males emerged before females. A pooled thermal threshold of 10.3°C was estimated for immature development. Development from hatch to adult emergence was estimated to take 473 DD.