Semi-field system. The walls and the roof of the semi-field system (SFS) are made of metal frames and fibreglass netting material. It was divided into four equal square sections divided by fibreglass netting. An experimental hut was placed in each compartment. The SFS  allowed replication of experiments within a short period of time. Laboratory reared mosquitoes were used and were available throughout the duration of experiments hence there were no delays as usually experienced in the field.