Adult mosquito traps are commonly used in biosecurity surveillance for the detection of exotic mosquito incursions or for the demonstration of elimination. However, traps are typically deployed without knowledge of how many are required for detecting differing numbers of the target species. The aim of this study was to determine the sensitivity
(i.e., detection probability) provided by carbon dioxide-baited EVS traps for adult female Australian southern saltmarsh
mosquitoes, Aedes camptorhynchus, a recent biosecurity problem for New Zealand. A mark-release-recapture study of three
concurrently released cohorts (sized 56, 296, and 960), recaptured over four days with a matrix of 20 traps, was conducted in
Australia. The detection probability for different numbers of traps and cohorts of different sizes was determined by random
sampling of recapture data. Detection probability ranged from approximately 0.3 for a single trap detecting a cohort of 56
mosquitoes to 1.0 (certainty of detection) when seven or more traps were used. For detection of adult Ae. camptorhynchus
around a known source, a matrix of traps provides a strong probability of detection. Conversely, the use of single traps
deployed over very large areas to detect mosquitoes of unknown entry pathway is unlikely to be successful. These findings
have implications for the design of mosquito surveillance for biosecurity.