my friend supposedly found a black widow spider near our trashcans so i went to check and found nothing. i looked again and saw a white egg sac. it's a little smaller than a dime and it's as round as a small playing marble. anyway, i'm wondering how to incubate the eggs so that the egg sac can produce viable spiderlings. i've never had experience with any kind of egg sac so any comments would be truly helpful. thank you.