Juvenile hormone suppresses their activity, and prevents the caterpillar from beginning metamorphosis too early.

保幼激素会抑制它们的活动，并防止毛毛虫过早开始变态。

Then, when it’s nice and plump, the caterpillar’s levels of juvenile hormone drop, which triggers it to stop eating and moving.

然后， 当它又好又丰满时，毛毛虫的保幼激素水平就会下降，这会触发它停止进食和移动。