Abstract: The catalase (CAT) activity of haemolymph in the silkworm, Bombyxmori (L.) exhibited a regular dynamic change through the larva-pupa-moth development. During larval stage, the CAT activity in any instar was higher at early and late stage than at middle stage; after pupation, the CAT activity rised rapidly and reached a peak at 48-96 h, then declined drastically until eclosion. The CAT activity of the male was higher than that of the female. There was great variation of CAT activity among silkworm races. Artificial diet could also affect CAT activity as compared with that fed on mulberry leaves. Both high temperature shock and fluoride solution administration could cause great change in CAT activity and the degree of change varied with silkworm race, sex, stage and administration dose. In view of above, it reveals that the CAT activity is closely related to larval develgpment, metamorphsis, as well as body metabolism, and the change of CAT activity under adverse conditions could be taken asone of the most important physiological index for larval resistance.

Key words: Bombyx mori (L.), catalase, resistance