Objective  Effect of ambient temperature on the growth and development of Harmonia dimidiata Fabricius was studied to determine the condition to encourage the beetle reproduction for serving as a biocontrol agent in the field.

  Method   H. dimidiata were fed on Ephestia kuehniella Zellerwere eggs and reared under a controlled temperature between 15 ℃ and 32 ℃ in a chamber to monitor the temperature effect on the development and survival of the predator. Threshold temperatures for developmental stages and effective accumulated temperature for growth were estimated by the least square method. Relationship between the chamber temperature and the beetle development was simulated with a linear diurnal equation.

  Result   The optimal egg hatching of H. dimidiata with a greater than 85% hatchability took place between 20 ℃ and 30 ℃. At 20 ℃, the rate of 87.5% for the beetles to reach adulthood was the highest. It was followed by 25 ℃ (82.50%)＞30 ℃ (77.50%)＞32 ℃ (45.00%)＞15 ℃ (35.00%). Either low temperature of 15 ℃ or high of 32 ℃ inhibited the growth of the beetles, but within that range, the development could still be completed with the rate hastened and the time shortened by increasing the ambient temperature. There was no significant difference in the time for entire beetle development in between 20 ℃ and 32 ℃. On the other hand, the duration was extremely significantly prolonged at 15 ℃ as considerable hindrance was imposed on the growth by low temperature. The threshold temperatures for various developmental stages of H. dimidiata were found to be at the highest level for the 2nd instar larvae at 12.74 ℃, the lowest for the pupal stage at 9.24 ℃, and for the egg-hatching at 9.87 ℃. The effective accumulated temperature required for the growth to maturity of a beetle was 324.82 d· ℃.

  Conclusion   Ambient temperature significantly affected the development, growth, and survival of H. dimidiata. Based on the survival rate and development time of H. dimidiate reared on E. kuehniella eggs for feed, 20-30 ℃ was determined to be the temperature range for optimal reproduction. The information obtained on the physiology of the predator would aid in the rearing as a potentially valuable biocontrol agent as well as in studying diapause of H. dimidiata.