This study determined the effect of temperature on the gonotrophic cycle of Culiseta melanura and developed a thermal heat summation model to calculate its duration under field conditions. A colony of Cs. melanura was used from New Jersey (F13-F17 generation) and the length of the gonotrophic cycle was observed at 2, 10, 16, 22, 28, 32 and 34 degrees C. None of the mosquitos survived at 2 degrees C or 34 degrees C and none laid fertile eggs at 32 degrees C. A linear regression analysis on the data showed that the thermal minimum for ovarian development was 6.4 degrees C and 95.87 degree days were required above 6.4 degrees C to complete one gonotrophic cycle. A thermal heat summation model is presented to allow calculation of the duration of the gonotrophic cycle under field conditions when average temperatures are known.