Abstract: In order to study digestive absorption and development of potato beetle Leptinotarsa decemlineata larvae feeding on the potato leaves grown from seed tubers （planting for 90 d） dressed with thiamethoxam and imidacloprid （18 g a.i./100 kg）, nutritional index of larvae such as food intake, body weight gain, food utilization efficiency, food conversion rate and approximate digestibility and pupal weight were tested with weighing method in the laboratory. The results indicated that the larvae feeding on the potato leaves grown from seed tubers dressed with 70% thiamethoxam ZF had significantly lower food intake, body weight gain, pupal weight, food utilization efficiency, food conversion rate, approximate digestibility and relative growth rate, and significantly longer developmental duration than those feeding on the leaves grown from seed tubers dressed with 10% imidacloprid WP and the blank control（P＜0.05）. On the contrary, seed dressed with 10% imidacloprid WP caused significant lower food intake and body weight gain in 3rd and 4th instar larvae compared with the blank control（P＜0.05）, while there were no significant difference in pupal weight, body weight gain in 1st and 2nd instar larva，food utilization efficiency, food conversion rate, approximate digestibility, relative growth rate and developmental duration than the blank control（P＞0.05）.The results suggest that 70% thiamethoxam ZF significantly inhibited larval food intake, causing it unable to meet their nutrient needs for growth and development. When L. decemlineata larvae fed on the potato leaves grown from seed tubers dressed with 70% thiamethoxam ZF, approximate digestibility and relative growth rate can be significantly reduced, and the developmental duration obviously prolonged, which may facilitate to reduce the seasonal number of generations so as to decrease the harm.

Key words: Leptinotarsa decemlineata；thiamethoxam；imidacloprid；seed dressing, food utilization；growth and development