An artificial leaf used for oviposition by the sweet potato hornworm, Agrius convolvuli (Lepidoptera, Sphingidae), was developed based on observations of adult behavior. It consists of a truncated cone disc sandwiched between a sheet of filter paper (top) and a plastic disc (bottom). The filter paper was kept moist by absorption of a leaf extract. Eggs were laid mainly on the lower surface of the plastic disc which was convenient for the collection of eggs. Oviposition behavior was well stimulated when the artificial leaf was supplied with the leaf extracts of fresh sweet potato leaves. Using a diluted ethanol extract (equivalent to 0.06 g fresh leaf/ml), 400-600 eggs/female were laid as many as when a potted plant was used. Observations using the artificial leaf revealed that the phytochemically-mediated oviposition behavior of this moth can be described as follows : 1) oviposition in both mated and unmated females is stimulated by the contact with phytochemicals of the host plant ; 2) in addition to high air humidity (>70% RH), moisture at the oviposition site is necessary to induce oviposition ; 3) egg-laying can be induced by host-plant volatiles alone although oviposition behavior is remarkably stimulated by both volatile and non-volatile compounds ; 4) chemoreceptors for the oviposition stimuli are located not only on the tarsi but also on the antennae ; 5) the tarsi are important to stimulate oviposition rather than the antennae ; however, 6) the antennae play an important role in the location of oviposition site. It can be concluded that the phytochemically-mediated oviposition sequence is accomplished through synergistic chemoreception by antennae and tarsi in A. convolvuli. Because of the high yield and the ease of egg collection, the artificial leaf is useful not only for the study of oviposition behavior, but also for successive maintenance of laboratory colonies of this insect.