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

A method of estimating the weight of individual Abgrallaspis cyanophylli (S ignoret) without the need for removal from the host plant is described. Usi ng this method, which enables accurate estimations of scale insect weight b y measuring length and relating it to a previously determined regression mo del, maximum feeding potential in male and female Chilocorus nigritus (F.) adults was examined at various constant temperatures over the range of 13 t o 30 degrees C and at a cycling temperature of 12 h/12 h at 14/30 degrees C (r.h. in the range of 62 to 68%). Mean daily potential food intake varied from 0.097 mg/day at 13 degrees C to 1.432 mg/day at 30 degrees C. However, intake at the cycling temperature was significantly higher than that at co nstant temperatures (1.98 mg/day). At 15, 20 and 30 degrees C there were no significant differences between male and female potential food requirement s whilst at temperatures in the mid range, there was a considerable increas e in female potential voracity when compared to that of the males. Maximum potential larval food requirement for development at 26 degrees C 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 bot h sexes to complete development. This study suggests that C. nigritus would be most efficient as a biological control agent if used in glasshouses wit h a mean daily temperature above 22 degrees C.