Both temperature and time of day influence the occurrences and frequencies of major types of ventilation inErythemis simplicicollisnaiads. Between 16 and 32°C, frequency of normal ventilation is linearly related to the temperature of an individual's ambient environment. Under constant temperature conditions, frequencies of normal ventilation are rhythmic within the diel: highest during photophase and lowest during skotophase. Gulping ventilation occurs more frequently at higher acclimation temperatures.