By the polyacrylamide gel electrophoresis (PAGE) and thin-layer scanning, the esterases (EST) of the third instar larvae of the Helicoverpa armigera were investigated in qualityand quantity after infection with nuclear polyhedrosis viruses (NPV). The changes in sort andcontent of hemolymph EST were examined at six hours postinfection and the numbers of ESTbands were from more to less as develop and infective time in larvae. The varies in EST patternbetween infection and control were not significant but the content of each band and the accumulation of EST were obvious. According to the changeable regularity in EST content of zymogram,the total and single content in diseased larvaes always gradually decreased with passages of infective time but in the healthy larvaes had no distinct changes. The results demonstrated that the infection with NPV could affect the EST metabolism in larvae hemolymph, and the metabolicchanges may show the infective level and extent, there fore it had indicated function.
