Large motor control and agility practice as they figured out how to maneuver over, under, and through the web... fine motor work too, as they carefully wrapped up little toy bugs in the web for the spider to eat. And the greatest little science lesson as they discussed why they were wrapping up those bugs: Child 1: "We are wrapping them up so the spider can eat them. Actually, they just drink their blood." Child 2: "Gross!" Child 1: "Yeah, but it's healthy for them. And if we drink blood it just goes into our tummy." Me: "Do people drink blood?" Child 2: "No! But we have blood inside us!"
This is the way learning is supposed to be...THEY chose the subject, and THEY chose how to go about their learning, which makes what they learn relevant and meaningful!