Sesami is one industrial plant with many advantage characters. But as other plants, sesami is infested by many insect pests. Sesami leaffolder Antigastra catalaunalis (Dup.) is one of most important pest which appeared very common and damaged sesaml production in Vietnam, where sesami is growing popular. To control this insect pest, farmer use chemical insecticides. But using chemical insecticides is not good any more for not only natural enemies, but a.lso effect on biological balance, environmental pollution, impact negative on human health. So, in order to protect sesami production and environment. Investigate studying on parasitoid of sesami leaffolder Elasmus sp. (Hym.: Eulophidae) is needed. The life cycle of Elasmus sp. was about 9.17 + or - 1.68 days under conditions of 29.9 + or - 2.8°C temperature and 78.5 + or - 3.7 percent humidity at photoperiod of 14L : 10D. Supplemental food quality affected adult longevity, as well as oviposition capacity. Individuals which were fed pure honey can outlive those fed with 50 and 10 percent honey solution (10.7 days compared to 8.8 and 5.7 days)
while those fed pure water lived only 3.9 days. And female can parasited 57.5, 44.8, 31.2 and 21.9 individuals of host with a number of egg of 241.4, 179.7, 128.5 and 87.1 eggs/female respectively. The behaviour of laying egg on host larvae of Elasmus sp. is agregated. Average number of egg laid by female on one larval host of 3rd or 4th instar is about 4.38 eggs/individual. In condition of laboratory (average temperature and humidity of 29.9 + or - 2.8°C and 78.5 + or - 3.7 percent), the emergence ratio of Elasmus sp. was 83.1 + or - 17.9 percent and sex ratio was 1male: 2.4females. The suitability of larval host was 2nd to 4th instars.