To prepare for this experiment you will need to do four things.

Maximize your screen in order to display as much of the web page as possible. Specifically, close or hide the various toolbars that clutter the top of your web browser. (Close or hide the Navigation, Location and Personal Toolbars.) Clean your computer screen of any dust. (Or, at least, most dust.) Make about a dozen tiny wads of soft paper and wet them. (If you know what "spit balls" are then, yes, that's exactly what I'm asking you to make.) When wet they should stick over the image of a moth to mark it. Test them to see that they will stick to and stay on the computer screen. Now adjust the brightness and contrast on your computer screen so that you can see both of these moths reasonably well. (Don't use maximum brightness or contrast.)

OK, here's what you're going to do.

The next page will show you an image of a polluted tree trunk full of moths and you will have 10 seconds to place your wet paper markers ("spit balls") on them. When time is up the next screen will appear (automatically) and you will have a chance to see all of the moths displayed on a revealing background.

Then collect data and write in your notebook the number of:

1. light moths you "hit" (those you marked with a "spit ball")
2. dark moths you hit
3. light moths you missed
4. dark moths you missed

Now, if you are ready and understand the instructions, leap to the next page and start hunting!