A strain of egg parasitoid, Trichogramma chilonis was developed for tolerance to insecticides and high temperature. The LC50 values were 13-folds higher for endosulfan, 233-folds for monocrotophos and 4- folds for fenvalerate. In high temperature, the developed strain could parasitise up to 53.3 eggs as compared to 6.7% by susceptible strain. Exact identification of developed strain was done using primers, viz., OPA-4,OPC-12 and OPL-4. Increased GST activity was recorded in developed strain, whereas decrease in carboxylestrase and similar acetylcholine activity to susceptible strain. Genetical studies with tolerant strain of T. chilonis revealed that female parent provide incomplete dominant characters and male provide recessive dominance. Partial sequence of Heat shock protein 70 (hsp70) was done for tolerant strain. Net house studies conducted on cotton, tomato and cabbage revealed that developed strain parasitised eggs to the tune of 60.0-70.0% as compared to 5.0- 15.0% by a susceptible strain. Field trials carried out on cotton, rice, tomato, cabbage, brinjal, okra and sugarcane proving efficacy of developed strain all over India.