Mosquitoes known to be involved in the transmission of Japanese encephalitis virus (JE) on Taiwan typically develop in rice fields. However, recent serological evidence indicated that JE virus was being transmitted on Liu-Chiu, a rice-free islet. To identify the mosquito vector in this unusual epidemiological situation, 4 mosquito species commonly found in Liu-Chiu were evaluated for their vector competence for a strain of JE (CH1392) virus isolated from central Taiwan. Armigeres subalbatus (Coquillett) was the most susceptible species, indicating its status as a potential vector. In addition, an isolate of JE (T1P1) virus from Ar. subalbatus collected on Liu-Chiu readily infected the salivary glands of orally infected Ar. subalbatus originating from Liu-Chiu. The infection rate reached 79% (11/14) after a 20-d period of extrinsic incubation at 28°C. We conclude that JE likely was transmitted between vertebrate hosts by Ar. subalbatus in this rice-free islet and that this species should be considered as a potential vector in similar ecological conditions.