Pan Traps

Pan traps are primarily used to capture micro Hymenoptera, but also trap many other insects. All you need for a pan trap is a small colored pan filled with soapy water. In fact, plastic bowls or plates using for picnicking are ideal. Use different colored bowls to catch different insects. Yellow, blue, white, and red are common colors used. To use the trap, just place a bowl on the ground and partially fill with water and a drop of dish liquid or other soap. The dish liquid is used to break the surface tension of the water, so the insects will fall through. Pan traps need to be checked at least daily. To collect the arthropods captured, the water is poured through a fine aquarium mesh net. It is then rinsed with water into a jar of 70% ethanol.

Links

http://iris.biosci.ohio-state.edu/sci/encyrtidae/pantraps.html
http://www.eman-rese.ca/eman/reports/publications/sage/sage13.htm
http://www.qmuseum.qld.gov.au/features/insects/collecting/yellowpantraps.asp