Beginning a Fairy Tale

My two daughters shared a small packet of peanuts for a snack while I was doing some chores. As I made my way back up from the basement, I spotted a lone peanut on a step not far from the trash. They must have dropped one and not realized it escaped the trash, I thought as I dropped it into the garbage. Not two minutes later my 4yr ran to me excitedly, "The spider ate the peanut!! It was in its area and now it's gone! The spider must have been hungry!!!"

Oops. Now the dilemma I face is: do I disillusion my daughters or do I allow the idea to continue that a spider (which could quickly and easily become a Borrower or a fairy) ate the nut and risk a regular pattern of feeding it on a semi-regular basis??
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Hopefully they'll just forget about the incident. If they try to continue feeding small bits I think I'll try to keep it in check while allowing a certain level of fancy to build for the sake of their imaginations. I wonder if whatever eats their occasional peanuts will someday leave a little gift behind for the two generous giants who take such an interest in providing meals for the little ones. But maybe we'll also do a unit study of some sort on what spiders REALLY eat...