ESTIMATING MORTALITY CAUSED BY PARASITES AND DISEASES OF INSECTS - COMPARISONS OF THE DISSECTION AND REARING METHODS

Because the measurement of insect mortality caused by parasites and di sease is fundamental to biological control and related fields, accurat e data are of great importance. Most studies rely on the rearing of ho sts to determine the incidence of disease and parasitism, and the resu lts are seldom compared with those determined by the dissection method . The examples in the current study show that parasitism measured by d issection was 12 to 44% higher than by rearing, and that dissections a re much more accurate than rearing for measuring the effects of parasi tes and disease, because dissection data are not confounded by the dis proportional mortality of parasitized hosts by disease and stress that occurs during the rearing process. Moreover, even parasitism data obt ained by dissections underestimate mortality because a considerable pr oportion of hosts die of oviposition trauma, and in some species, afte r being fed upon by female parasites before they are sampled. The rear ing method is useful for determining parasite species as well as other purposes, and these are listed along with the numerous advantages of dissections. Although dissections provide the most accurate mortality estimates, for the most comprehensive results, both rearing and dissec tion methods should be used concurrently.