Abstract: Adult flight capabilities of three major rice stem borers, Tryporyza incertulas, Chilo sup=pressalis and Sesarnia inferens were determined with flight mill and computer system. The results show that the moths of T. incertulas and C. suppressalis have similar flight capability. Normal flights took place within four days after emergence, and they had no conspicuous pre-repro ductive period and calling and mating could occur whithin 24 hours after emergence. Motlhs within one day after emergence in the second phase of ovarian development had the strongest flight capability. The cumulative flight distance of a female moth was determined to be over 32 kilometers. Female moths showed longer flight duration while most of the male moths made irregular interval flights affected easilty by physical conditions. Flights of thse two species were closely related to calling, mating and ovipositlon behaviours, showing typical mating flight syndrome. Though most flights in the field were trivial, the longest dispersal distance could be over 100 kilometers. The moth of S inferens had the strongest flight capability among the three rice stem boreres and the flight distance of female and male moths were over 32 and 50 kilometers, respectively. Normal flight could occur during the first six days of adult life. The pre-reproductive period were two to three days. Adults in the second phase of ovarian development made the longest flights. Thler flight capability declined with the development of the ovaries. This species has flight capability of long distance dispersal and possesses physiological and behavioural bases of migration flight.

Key words: Tryporyza incertulas——Chilo suppressalis——Sesamia inferens flight capability