Ishaaya, I., The Volcani Institute of Agricultural Research, Division of Entomology, Bet Dagan, Israel
Swirski, E., The Volcani Institute of Agricultural Research, Division of Entomology, Bet Dagan, Israel

A reaction mixture of pH 6·0 at 37°C for 60 min reaction plus 0·5% sucrose was found to be the optimum for invertase activity in both the Florida red scale (Chrysomphalus aonidum) and the California red scale (Aonidiella aurantii); a reaction mixture of pH 5·5 at 30°C plus 0·5% starch for 4 min was found to be the optimum for amylase activity in the Florida red scale and the same reaction condition for 10 min for amylase activity in the California red scale. The invertase activity in both scales was found to be greater than the amylase activity and more stable at high temperatures. A decrease of about 30 per cent in the invertase activity was found in starved insects 1 day after the removal of the scales from their host. Various host plants were found to have no effect on the California red scale invertase and a slight effect on the Florida red scale invertase. At a temperature below the threshold of scale development (2 and 8°C), a decrease of about 30 per cent in invertase activity was recorded. At higher temperatures such as 32°C, the Florida red scale invertase was found to be physiologically better adapted than the California red scale's. Mineral oil, which is usually used for armoured scale control, was found to affect the invertase activity of both scales. © 1970.