Abstract
The female parasite, Chrosocharis pentheus, kills larvae of the Ranunculus leaf mining fly, Phytomyza ranunculi, by host-feeding and parasitization. Daily host mortality from parasitization and host-feeding by C. pentheus tended to fluctuate periodically during its life. The former mortality changed in parallel with the change of the latter mortality occurring a few days earlier. Besides more frequent host-feeding activity appeared for a while after emergence, such an expression of host mortality would have arisen from the precedence of parasitizing activity over host-feeding activity in the sequence of host attack during a day and the effect with the time lag of a few days (corresponding with the period required for the complete development of eggs), of host-feeding activity upon parasitization. Total host mortality from host-feeding was closely related to the life span of C. pentheus but that from parasitization was not. The ratio of the latter mortality to the former, though varying widely among parasites, was about 0.5 on an average.
