Seven selected CO2 flow rates were statistically evaluated using modified CDC traps supplied with CO2 from a single source. The 500 ml per min (0.1214 Ib per hr) flow rate was found to be the optimum for trapping Cnephia mutata and Prosimulium hirtipes. The operating performance of supplying CO2 from a single source one 20 Ib (net) cylinder via hoses to multiple CDC traps was considered advantageous with respect to ease in selecting specific flow rates, logistics and cost analysis.