Swarms and emergency exoduses of Aedes taeniorhynchus mosquitoes produce sounds detectable from 10 to 50 m in a quiet environment. Background noise levels as low as 21 dB (decibels referenced to 20 microPa) are present at dusk between frequencies of 0.3 and 3.4 kHz. A mosquito swarm with a sound pressure level of 25-35 dB is detectable over tens of meters in the marsh, if not in the 40-60-dB background noise of a typical urban environment. Individually caged Ae. taeniorhynchus also are detectable, but only with 2-5-cm distances where the sound pressure level rises to 22-25 dB. These differences between signal and noise levels indicate that it is technologically feasible to construct an acoustical device for remote surveillance of large swarms or emergence exoduses of Ae. taeniorhynchus. This device could also detect nearby individuals attracted to a bait. Such a device can distinguish males from females by their wingbeat frequencies (700-800 Hz vs. 400-500 Hz).