Genetic variation lies in this generation of crickets; some are brown and others are a much lighter brown almost a gray.
Their main predator are birds and they need food not only for themselves, but for their young ones if they have chicks.
The cricket's home should help them survive; it's their home. But not for all. The lighter crickets aren't the same color as their home's trees, so they are spotted easily by their predator's sharp vision.
As the ones who are left weren't seen by their predator they have survived. Since the others got eaten they didn't get a chance to reproduce. Therefore, the brown-colored crickets are able to reproduce.
The brown ones who were able to survive and not get eaten will be able to help their offspring by passing their genes of their color. This will benefit their species because it allows them to stay alive.
This has led to changes in the species' gene pool, because the brown color benefited them to survive up to an age where they can reproduce. Conversely, the lighter crickets were seen very easily which didn't let them grow up to an age where they can reproduce.