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On the next page, you will be challenged to figure out how to test some of the hypotheses for the function of the TO. This page will prepare you for that exercise, by working through an example.

1. Start with a hypothesis
2. Decide what kinds of factors you would want to measure to test the hypothesis
3. Predict the relationship between the factors that you expect to see if the hypothesis is correct
4. Devise a test based on your prediction

1. Let's say you have an idea that the larva uses TOs to advertise to attending ants that this particular larva has a lot of nectar to give -- the "advertisement hypothesis."

2. You decide that the factors related to this hypothesis are the use of TOs and the number of nectar droplets produced by a larva.

3. Your prediction: if the function of the TOs is to advertise the profitability of the caterpillar, then we expect that as the number of TO extrusions rises, the number of nectar droplets secreted will also rise (a positive relationship).

4. Test: you observe many different larvae under controlled circumstances, and count the number of times each larva extrudes the TOs, and the number of nectar droplets each produces.

Does this mean that if you do find a positive relationship, that the hypothesis is proved right? No; instead we merely conclude that the data are consistent with the hypothesis.

Why? For one thing, because the positive relationship could be due to other functions of the TOs. For example, it could be that both TOs and nectar droplets function to call ants, and if the larva perceives itself to be in danger, it will increase both TOs and nectar droplets.

Next: you make the predictions