As an example, let's consider the response to light and dark.
Instructions Draw a line down the middle of the dish.
Now place a known number woodlice on the dish and allow them to move about a bit so they are randomly distributed. Count how many woodlice are on each side of the line, then place the piece of black card over half to the dish to make that half dark. At intervals of 30 seconds count how many are on the light side. Continue for a few minutes. This can be done easily, and you could investigate different leaves to see if they contain the same chemicals in the same ratios.