Abstract: Since the years 1950, the defoliations caused by gypsy moth in Corsica are recorded inthe forest service archives. This pest sometimes induces important defoliation damages thatspread some years throughout several thousand hectares. Gypsy moth population dynamics inCorsica is cyclic, alternating a culmination and a latency phases in a ten years’ interval. Since theend of the last gradation in 2003, the male moth populations were monitored using pheromonebaited traps and the eggs masses numbered each year in the south of Corsica, in order to establishan early warning method enabling to detect the beginning of a new gradation. The analysis of thesamplings made until 2007 suggests that a new gradation would probably start in the next future.