Abstract: All parameters of the insect life cycle (fecundity, survival, rates of development and growth, and body mass) are characterized by phenotypic plasticity, which ensures adjustment of the seasonal cycle to local conditions: temperature, day length, and diet. At the same time, the nature of dependence of the developmental rate on the temperature can vary. We have studied the photoperiodic and trophic plasticity of the thermal reaction norms for preimaginal development (the temperature threshold, thermal sensitivity coefficient, and sum of degree-days) and adult body mass in the Asian ladybird Harmonia axyridis from the autochthonous Tomsk population. The thermal reaction norms for development of the eggs laid by females that fed on eggs of the grain moth Sitotroga cerealella or on the green peach aphids Myzus persicae did not differ significantly, although when females fed on aphids, the eggs developed 3–4% faster at all the temperatures (17, 20, 23, and 26°C). The total duration of larval and pupal development was studied using 16 combinations of conditions: temperatures of 17, 20, 24, and 28°C, photoperiods of 12 and 18 hours of light per day, and two diets (grain moth eggs and green peach aphids). The development of the larvae feeding on moth eggs slowed down significantly as the temperature rose from 17 to 28°C: by 24–16% under long-day and by 27–17% under short-day conditions. The temperature threshold of total larval and pupal development increased significantly, while the slope of the regression line of developmental rate on temperature decreased, i.e., the thermal sensitivity of development decreased. Under short-day conditions, the development accelerated significantly at temperatures of 17–24°C: by 15–2 and 10–2% when the larvae fed on aphids and moth eggs, respectively. At the same time, the temperature thresholds and the thermal sensitivity of development decreased and were significantly different. Depending on the photoperiodic and trophic conditions, the body mass of females and males either increased with the temperature rising from 17 to 24°C, or did not demonstrate an unambiguous relationship with temperature. © 2025 Elsevier B.V., All rights reserved.