Abstract
The average pH values obtained with a capillary glass electrode are Pieris, last instar 7.17, next to last instar 6.9; Heliothis, last instar 7.23, next to last instar 6.79. The buffer value near pH 4.5 is 0.01 for Pieris and 0.015 for Heliothis. The buffer value of the last instars is higher than that of the previous instars.