Investigations on the biology of Phlebotomus papatasi were carried out under laboratory conditions at 28 +/- 2 degrees C and 80 +/- 1% RH. Fecundity of the female varied between 61 and 48 (mean 56.2 +/- 5.46) and the incubation period of eggs ranged from 7-9 (mean 7.81 +/- 0.61) days. The developmental duration of larvae and pupae varied from 24 to 31 (mean 28.57 +/- 2.71) and 9 to 11 (mean 10.38 +/- 1.51) days, respectively. The rate of insemination, determined from the females that laid fertile eggs, was found to be maximum when the females were three days old. Autogeny was observed from female sandflies, emerged from the larvae fed on animal liver powder. The duration of first and second gonotrophic cycles under ambient conditions was shortest in summer and longest in winter. Studies on adult longevity showed that the females fed on mouse blood survived for 6 to 27 days (mean 14 +/- 12.5 days).