Effects of the pars intercerebralis (PI) on the rate of oviposition were examined in adult females of Riptortus pedestris (F.) under long-day conditions that promote reproduction. When the neurosecretory cells in the PI were surgically removed from the females, they laid significantly fewer eggs than control females. When the PI from reproductive females was transplanted to PI-removed females, the number of eggs was significantly greater than that in PI-removed females without transplantation. Therefore, we suggest that the PI neurons promote fecundity or oviposition in R. pedestris.