Diuresis in the first 20 min after emergence was examined in males and females of Culicoides melleus and Culicoides variipennis. Both sexes of both species excreted most fluid (estimated as drops per minute) in the period between 2 and 8 min after emergence. Culicoides melleus adults, however, were more productive than C. variipennis. Males of both species excreted significantly more drops of fluid than females within the 20 min period of observation. Measurement of the sizes of drops excreted by C. variipennis showed that the largest drops were eliminated immediately after emergence.