Evolution is a long and intricate process that involves adaptation and species interaction as well as environmental variables. As an example lets just say spider web is red, the spiders traditional prey cannot see red so he eats well. The prey species has a few members who mutate and see red so these few do not get eaten. They have little red seeing babies that also grow up and have lots of babies until eventually all surviving members see red. Many spiders starve but a few have babies that spin pink webs....the prey cannot see the pink so well so these spiders eat pretty well and have lots of babies, a few of which make faded pink webs. Rinse and repeat until pink fades completely and webs become clear. Now we have well fed spiders and insects that cannot see their webs but in a thousand generation they will see the webs and spiders will evolve something new.