This method is by far the most favorite way of catching and trapping mosquitos. The red thermos contains dry ice (solid carbon dioxide). This is what attracts the mosquito. Connected to the thermos is a little tube that the CO2 evaporates into. To make the trap effective the tube must be on top of the fan.

The end of the tube connects to a fan. The fan in this photo is in the clear container underneath the silver pan (for rain protection). The fan sucks the mosquito into a net.