Study conducted on biology of Liriomyza trifolii (Burgess) (Diptera : Agromyzidae).on cotton, castor, cowpea and tomato at Raichur, Karnataka during 1995-96 revealed that the egg, larval prepupal and pupal varied from 2.59 to 3.74 days, 3.93 to 4.05 days 62 to 75 minutes and 9.82 to 10.65 days, respectively. Egg size varied from 190 to 196 µ in length and 103 to 116  µ in width while the size of puparia ranged from 1.46 mm to 1.69 mm in length and 0.59 to 0.81 mm in width on various hosts. The male and female longevity varied from 2.56 to 6.90 days and 4.69 days and 4.69 to 9.80 days, respectively. The total life cycle ranged from 19.19 to 24.69 days for male and 21.32 to 27.59 days for female. Fecundity varied from 64.1 to 158 eggs and the ratio of ovipositional to feeding punctures varied from 1: 5.37 to 1: 8.55 on different host plants.