Abstract: To compare and estimate the cellulose enzyme activity in different insects, the paper presented a comprehensive analysis of enzyme activity from the gut juices of four herbivorous insect species (larvae and adults of three leaf-eating beetles, Chrysomela populi, Ambrostoma quadriimpressum and Gallerucida bifasciata, and larva of a trunk-borer, Semanotus bifasciatus). The results showed that there were complete cellulase systems in these four beetles, and that both temperature and pH had a significant impact on the enzyme activity in the gut contents. For both larvae and adults of three leaf beetles, the optimal conditions of enzyme activity were 40-60 ℃ and pH 4-6, and the enzyme activity could not be detected under high temperature and high pH conditions. However, in trunk-borer of S.bifasciatus the highest enzyme activity of exoglucanase (C₁) was observed at pH 9 and 70 ℃. In addition, the enzyme activities of endoglucanase (Cx) and β-glucosidase in S. bifasciatus were lower than that of the leaf beetles, while the enzyme activity of C₁ was much higher than that of these leaf beetles. The results indicated that temperature and pH had significant influence on insect cellulose enzyme activity. The different feeding habits and the phylogenetic relationship may result in different enzyme activity.

Key words: leaf beetle, longhorn beetle, cellulose, temperature, pH value