This study was conducted to elucidate and to compare some factors which influence the host-seeking behaviour of adult female simuliids in two geographically isolated regions. Various observations and experiments were performed with the knowledge of a mechanism inherent in the feeding behaviour of simuliids. This approach has helped to clarify the orientation of simuliids to their hosts and has enhanced the understanding of the transmission of parasites by these flies. Further, it was found valuable to determine whether the behaviour state of simuliids influenced their reaction to visual stimuli. / Thesis / Master of Science (MSc)