Cabbage webworm,Hellula rogatalis(Hulst), development on broccoli was determined at five constant temperatures ranging from 15 to 35°e. At 15°e, egg to mature larva was 119.4 d, but larvae failed to pupate. Development from egg to death of the adults was 89.9, 42.8, 34.0, and 22.8 d at 20, 26, 30, and 35°e, respectively. Fecundity increased with temperature between 20 and 30°e, with a maximum of 161.5 eggs per female at 30°e, but decreased to 8.2 at 35°C. Most eggs were laid on the upper surface of the broccoli leaf. No eggs hatched at 10°C, but at 15°C, egg hatch was 19.1%, and increased to 89.3% at 26°C. There were five instars; head-capsule width for the first through fifth instars was 0.19, 0.29, 0.49,0.78, and 1.20 mm, respectively. The first two instars mined the leaf; later instars fed on the under surface of rolled leaves, within spun webs, and the last two instars fed on the leaf as well as the midrib, breaking it in two. The constant temperature data obtained were used to construct developmental time function curves using the population model design system software program.