Maximum feeding potential of larvae and adults of the scale insect predator, Chilocorus nigritus with a new method of estimating food intake

摘要

A method of estimating the weight of individual Abgrallaspis cyanophylli (Signoret) without the need for removal from the host plant is described. Using this method, which enables accurate estimations of scale insect weight by measuring length and relating it to a previously determined regression model, maximum feeding potential in male and female Chilocorus nigritus (F.) adults was examined at various constant temperatures over the range of 13 to 30 ℃ and at a cycling temperature of 12 h/12 h at 14/30 ℃ (r.h. in the range of 62 to 68%). Mean daily potential food intake varied from 0.097 mg/day at 13 ℃ to 1.432 mg/day at 30 ℃. However, intake at the cycling temperature was significantly higher than that at constant temperatures (1.98 mg/day). At 15, 20 and 30 ℃ there were no significant differences between male and female potential food requirements whilst at temperatures in the mid range, there was a considerable increase in female potential voracity when compared to that of the males. Maximum potential larval food requirement for development at 26 ℃ and 62% r.h. in C. nigritus was also estimated using the above method. A mean of 16.24 mg of Abgrallaspis cyanophylli (Signoret) was required for larvae of both sexes to complete development. This study suggests that C. nigritus would be most efficient as a biological control agent is used in glasshouses with a mean daily temperature above 22 ℃.