Roll the index card into a funnel and fit it into the mouth of the catcher-container. Be sure that the bottom funnel hole is very small and that it does not touch the food in the catcher-container. If the funnel and the food touch, the flies will crawl in and get trapped in the moist food and drown. Wrap the mouth of the catcher-container and the funnel with parafilm to keep the funnel secure. Clear this project with store owners and check on your catcher-container every 24 hours.
Warmer weather is best for collecting flies.
Once you have trapped some flies, you can examine them under a dissecting microscope. Count and sex them. Classify the flies according to mutations or species. Examine this data and set up graphs comparing the number of organisms in particular locations or the number of males versus females for particular traits, etc. Draw the different kinds of flies you have captured and exchange and compare this information with students doing this project in other parts of the country.