Wilbur the pig had been so attentive to Charlotte's egg sac, waiting all winter for the babies to emerge, that he was beyond delighted when all the little spiders hatched. He greeted them enthusiastically, and they responded with a chorus of "hello"s. However, only minutes later that changed to a series of "good-bye"s as each little spider spun out their silk balloon and floated away.
Baby spiders are designed to move quickly and spread out far from where they hatched. With hundreds of babies emerging from the egg sac all at once, they could not all stay nearby or there would not be enough food for them. Wilbur, of course, does not think this way, and he is heartbroken as the spiders wave farewell and float off in the wind.
As it turns out, three of Charlotte's babies do decide to stay in the barn. Wilbur helps them decide on names, and they end up with Nellie, Joy, and Aranea. These three keep Wilbur company, and as the years go by, a few spiders from each generation do stay in the barn where they were born. None of them, however, can truly replace Charlotte.