Abstract
Life-history parameters of two species of spider mites, Eotetranychus uncatus GARMAN and Eotetranychus tiliarium (HERMANN), were investigated at 25±1°C and 15L-9D. For the latter species, two populations were studied, one from Alnus japonica (THUNB.) and the other from Alnus hirsuta TURCZ. The total developmental time was shorter in E. uncatus than in the two populations of E. tiliarium. The intrinsic rate of natural increase (rm), net reproductive rate (R0) and mean generation time (T) were as follows : the Betula platphylla var.japonica (MIQ.) population of E. uncatus : rm, 0.198, R0, 32.68 and T, 18.69; the A. japonica population of E. tiliarium : rm, 0.178, R0, 34.29 and T, 21.04; the A. hirsuta population of E. tiliarium : rm, 0.169, R0, 31.14 and T, 21.71.
