Radioisotope technique for estimating lady beetle consumption of tobacco budworm eggs and larvae

Females of the tobacco budworm, Heliothis virescens (F.), were fed Phosphorus-32 (in NaH232PO4)in a 10% sucrose solution. Eggs and larvae of the moths were assayed for radioactivity before feeding them to the adult lady beetles, Coleomegilla maculata DeGeer. The adults were assayed for radioactivity each day for 10 days after consumption of the eggs or larvae. Radioactivity levels in the lady beetles showed a gradual decline each day after consumption of egg or larvae. Prediction equations from regression analysis indicate that the number of eggs or larvae eaten by adult C. maculata can be predicted in laboratory or field studies after determining radioactivity of H. virescens eggs or larvae prior to lady beetle consumption.