The flight periods and direction of flight ofStenopsyche angustata(Stenopsychidae),Macrostemum fastosum, M. lautumandPolymorphanisus astictus(Macronematinae: Hydropsychidae) were investigated from May 1983 to June 1984. Light trap catches indicated thatS. angustataadults were present throughout the year, whilst Macronematinae were most numerous in May and June and were not recorded during autumn and winter. Temperature may determine the flight period of Macronematinae in Hong Kong's seasonal tropical climate, but timing of emergence to reduce mortality of late‐instar larvae and pupae during wet season spates would produce the same temporal pattern.