Effect of Humidity on Life of Experimental Lasioderma serricorne (Fabricius)

Effects of environmental humidity on the growth, reproduction and survival of the Lasioderma serricorne population in laboratory were studied. Varied relative humidity, i. e., (50±5)%, (60±5)%, (70±5)%, (80±5)% and (90±5)% RH, at (32±1)℃ with a photoperiod of 14-h-L:10-h-D were applied. The results showed that (1) L. serricorne failed to completely develop a single generation under 50% or 90% RH-the first generation larvae died at 90% and the second instar perished at 50%, but it could under the other humidified conditions in the test; (2) there were no significant variations in the egg development time under the tested RHs, except 70% and 90%; (3) the larval developments were similar under 60% and 70% RH, however, at 80% RH, the duration of the 1^st stage (i. e., 8.08 d), 2^nd stage (i. e., 6.82 d), and 3^rd stage (i. e., 7.05 d) were significantly shorter than the others; (4) the longest life span of 25.84 d was found in female adults at 60% RH, and 15.25 d in males at 80% RH; (5) the shortest pre-oviposition period of 2.55 d, the total pre-oviposition period of 58.41 d and the oviposition period of 7.00 d were found when the RH was 80%, but no significant difference at 60% or 70%; (6) there were significant differences on the fecundity, age-stage life expectancy (e_xj), and age-stage specific reproductive value (V_xj) of the insects reared under 60%, 70% or 80%, and they peaked at 60% RH; (7) the net reproduction rates (R₀) decreased from 37.69 at 60% to 30.65 at 70% and 15.02 at 80% RH, whereas, the intrinsic rates of increase (r) and finite rates of increase (λ) showed no significant differences as the RH was altered; (8) there were no significant differences on the generation times (T) of 72.68 d at 60% and 72.79 d at 70% RH, but they were significantly longer than 62.80 d at 80%; and (9) the lowest larval counts were found on the 60^th d under 60%, the 50^th d under 70% and the 38^th d under 80% RH, and escalated significantly afterward suggesting an optimal time for the insect control.