Why silkworm was white and thin and exhausted in chapter 23

In Chapter 26, the Centipede begins singing and dancing so vigorously that he falls off the edge of the peach. Everyone is startled to see him tumble farther and farther down, and everyone believes that they will never see the poor Centipede again. Yet James jumps to action and orders Silkworm to begin spinning, even though she is tired (from spinning); he then takes Silkworm's rope and leaps down to rescue Centipede. Silkworm is then exhausted.