Abstract: The effects of water temperature on egg laying and hatching in vitro were investigated, and egg laying and development in vivo at 20℃ were also characterised. The results indicated a positive correlation between mean egg production and temperature in vitro, and the mean egg production was 5.9, 9.1, 9.2 and 13.4 eggs/worm at 10, 20, 30 and 35℃, respectively. Except 4℃, majority of the eggs were laid during the first 5h. However, egg laying of the mature worms was continuous and uniform, with a mean 6.5 eggs/worm at 20℃ per day. Although the hatching time and the duration of hatching declined with increasing temperature, with 19d, 3d, 2d, 36h and 24d, 5d, 5d, 3d at 10℃, 20℃, 30℃ and 35℃, respectively, the highest hatching success was observed at 30℃. Ninety percent of worms reached maturity within 7 days post-infection when exposed to 20℃. The life-cycle of D. vastator from egg to sexual maturity lasted for 8 to 11 days which indicated that a second treatment should be administered a week later at 20℃.