Egg release rates at different abdomen temperatures were determined for 2 populations of Erythemis simplicicollis (Say) by submerging females’ abdomens in vials of water of known temperature and timing the durations of egg flow. The log of flow rate increased linearly with increasing abdomen temperature in both New York and Florida (N=29 and N=62 respectively) from 18 to approximately 38° C above which flow rates decreased or ceased. Significant differences were found in the slopes and elevations of the regression of log egg flow on temperature for the two populations, the N.Y. females releasing eggs from 67% to 8% faster than the Florida females between 20 and 38° C respectively. The Q,0 of flow rate with temperature was 1.8 for the N.Y. females, and 2.2 for the Florida population. Comparing lOspp. in the Libellulidae, egg flow rate at a given temperature increased significantly with increasing body size.