Penfluron and diflubenzuron, both chitin synthesis inhibitors known to be highly effective against nymphs ofPoekilocerus pictus(F.), were tested against the adult for their possible effects upon reproduction. These compounds were found to have the maximum effect, when no eggs were laid, if both sexes were treated. The eggs of treated males × untreated females did not hatch and those of treated females × untreated males gave rise to nymphs which died before reaching maturity.