Certain species of bugs have developed a really bad taste so predators won't eat them (at least, that's what I've read. I haven't personally done insect taste tests).
Did they actually evolve in that direction? What is the evidence?
Let's look in Dr. Grumpy's break room:
Post Halloween day #1: Everyone brings their leftover candy to the office. We put it in a big bowl in the break room. We are too damn sick of candy to touch it.
Post Halloween days #2-3: Predators (okay, me, Pissy, and the staff) arrive. The choicest (i.e., chocolate) items disappear first. Reese's PB cups, M&Ms, Milky Way, Snickers, Kit-Kats, Twixt, Butterfingers, Three Musketeers.
Post Halloween days #4-5: Other stuff starts to go. Skittles, Laffy Taffy, Smarties, Runts, Starbursts.
Post Halloween days #6 and on: This is when we find the survivors. Just like the unpalatable bugs, some candy types will sit there for quite a while. Candy Corn, Tootsie Rolls, Circus Peanuts, and those horrible taffy things in black and orange wrappers (the latter, I suspect, were only made once in the 1960's and have since just been re-gifted. I think people who got them as kids now give them out as adults, and the cycle continues).
Granted, I have no evidence to suggest that Darwin's staff dumped leftover candy at the office. If they did, however I'd suspect that's more likely to have led him to the theory of evolution than a trip to the Galapagos.
For more background on truly horrible Halloween candies, read this.