Functional responses of Iphiseius degenerans and Neoseiulus teke (Acari: Phytoseiidae) to changes in the density of the cassava green mite, Mononychellus tanajoa (Acari: Tetranychidae)

The functional responses of protonymph and adult female Iphiseius degenerans and Neoseiulus teke to increasing density of three stages of their prey, the cassava green mite (CGM), Mononychellus tanajoa, were studied on excised cassava leaf discs under laboratory conditions. The responses obtained were predominantly sigmoid type III curves with the highest plateau when both stages of I. degenerans and N. teke were preying on CGM eggs. In all cases, the predation rate of the former species exceeded that of the latter. The empirical data were fitted by four different models. From the models, the attack coefficient (a) and handling time (T _h) were estimated. For a given predator stage (protonymph or adult female), the predator's attack coefficient declines and handling time increases as the prey gets larger. For a given prey stage, the predator's attack coefficient increases and handling time decreases as the predator stage becomes larger.