Ecological Studies on Anagrus incarnatus Haliday (Hymenoptera : Mymaridae), an Egg Parasitoid of the Rice Planthoppers : I. Functional Response to Host Density and Mutual Interference

Abstract

The functional response to host density and mutual interference of Anagrus incarnatus parasitizing eggs of the rice pest Nilaparvata lugens were studied in Japan. The behavioural response to varying host egg densities fitted the Type II functional response of C.S. Holling; using his method (1959), the handling time (Th) and searching efficiency (a) were assessed. Using the model of M. P. Hassell & G.C. Varley (1969), some degree of mutual interference (m) among the parasites was detected. Observations on the sex ratio of the parasite progeny in relation to the host egg and searching parasite densities used in the present studies showed that the ratio was fairly constant, the females usually outnumbering the males by about 2 or 3 to 1.