Statistical ysis biological?

I won't go into the gorey details, but here's the basic problem. I've done an experiment and have found no significant difference between two groups of ant performing a task. Now, it's just occurred to me that I don't know if the no difference is that they both CAN perform the task, or that they both CAN'T. How can I find this out statistically? Think maybe I'm just tired and confused and that this is really obvious...