A newly developed apparatus for maintaining Simulium adults is described in which the emphasis is placed upon good air conditioning and the maintenance of high humidity in the holding chamber. Improvements on the safety caps and the use of polystyrene, plastic material and nylon gauze with special hygroscopic qualities led to a maximum survival time of 4 weeks in different species. The advantages of the apparatus are its simplicity of construction, its potential for use in areas lacking electricity and the possibility of maintaining Simulium adults in different stages of development, such as blood digestion, egg development and oviposition, under controlled conditions.