The American serpentine leaf miner, Liriomyza trifolii (Burgess) was observed as an important pest of tomato crop. Studies were conducted on the biology of the pest, its reaction towards cultivated genotypes of tomato for host plant resistance and to test the efficacy of selected insecticides. The serpentine leaf miner, mines the foliage of tomato and many other plant species like cucurbits, vegetable pea, chrysanthemum and other cultivated annual flowering plants etc.Mated female insert their eggs inside the leaf punctures on upper and lower surface on tomato leaflets. After hatching, the young larvae mine through the palisade and mesophyll tissues and remain in the leaflet until three larval stage/instars are completed. Mature third instars larva exit from leaflet and drop on the ground to pupate. However, some larvae pupate on the leaflets or fruits of the tomato plant. Adult emerge from puparia in about seven to ten days depending on the temperature. Feeding punctures/egg laying punctures cause miner injury to the leaflets. Such punctures appears as chlorotic depression in the leaflets. Larval mining cause greater injury.