Dsitribuição espacial de Coenosia attenuata Stein (Diptera: Muscidae) e das suas presas em estufas de hortícolas na regiao Oeste, Portugal

The spatial distribution of the predator Coenosia attenuata Stein (Diptera: Muscidae) and of insects known as its preys, namely whiteflies and leafminers, amongst others, was studied in greenhouses of cucumber, sweet pepper and tomato, in “Oeste” region (Portugal). Thrips were included in this study. Whiteflies and thrips were the most abundant and, like C. attenuata, they were more abundant on cucumber than in sweet pepper and tomato. It was not detected a generalized border effect for C. attenuata, thrips and whiteflies, neither an equal preferential horizontal distribution of predator and preys, in the rows and sectors of the crop. C. attenuata preferred the sunny crop rows, while whiteflies and thrips showed a tendency to be located in shadowed rows. In terms of vertical distribution, whiteflies preferred the lower page of leaves of the higher layer (in cucumber) or the lower one (in sweet pepper). Thrips preferred the flowers of the medium layer in cucumber; flowers of the higher layer in sweet pepper were also very attractive (those of the lower layer were not analysed). The predator was mainly located in the upper page of leaves in cucumber and sweet pepper, while in tomato it chose the tutor, and not the plants. In all greenhouses, the predator was also found settled in their structures (wooden bars, wires, tutors).