Evaluation of Mortality Factors with Special Reference to Parasitism of the Green Rice Leafhopper, Nephotettix cincticep Uhler (Hemiptera: Deltocephalidae)

Abstract

A superficial comparison of the numbers in a population killed by different mortality factors is by itself misleading. This arises from the fact that each mortality factor seldom acts alone but has interactions with each other either sequentially or contemporaneously. Since we have no information on the relationship among mortality factors within the egg stage of the green rice leafhopper, several assumptions about their modes of interactions were made to measure the amount of mortality that each factor would cause if it were operating alone. In every hypothetical case, the proportion of eggs parasitized increased with the increase of egg density. This suggests that the egg parasite operated density-dependently against the host density. This tendency was quite evident in the early and mid-season paddy. From field and laboratory experiments it follows that the egg parasite was able to respond positively to host density. © 1972, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.