i have just discovered that "tarantella" in english is used to indicate the spider... in italian is just the folkloristic dance from southern Italy (the spider itself is named "tarantola"), so i was at first a little confused, thinking about PCs encountering a lot of people dancing around a tree stomp

I like the way it looks; maybe a little dark, but i suppose this small clearing is surrounded by trees shielding the sunlight... and a giant spider is more scary in shadow than in plain sight!

May i ask how many pcs counts the party? How do you expect the encounter to evolve?
I am asking about, because i ever try to predict how the player will react and so i prepare the battlefiled accordingly to my ipothesis; i was wondering about the way others DMs set up the scene.