Y: Now that we've seen how you tell stories, Don, I'm going to tell      a story this time. And this story is going to be about the life of a      certain female dung beetle. I'll call her Gerta. When Gerta finds a      nice piece of dung she digs a tunnel through it and down into the      earth below. Next she pulls small pieces of dung into the tunnel with her, making it      into little balls that she can lay her eggs in. She lays one egg into each ball of dung.      And when the eggs hatch each larva feeds on its ball of dung in peace.

D: Okay, but surely she's not so exact that each ball of dung is the same size. What if      they vary in size? Will one baby be fat and one skinny?

Y: The amount of food does affect the size of the dung beetles. In fact, if a male larva      gets plenty of food early on he will grow big in size, and he will grow horns to match.      But if a male larva gets little food he will grow to be small, and he will grow either      very small horns or no horns at all.

D: I think you're leaving an important part out--the mating itself. Which male does she      prefer--the big, horned male or the little puny hornless male? Or do horns even      matter?

Y: Actually, they don't. About half the population of male dung beetles are big and      horned, about half small. Gerta will mate with whoever can make his way into her      tunnel.  

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