Cecropia moth freshly emgered from its cocoon.
Silkworm life cycle.
Cecropia moth life cycle.
Dimorphic cocoons - baggy (left) and compact (right).
It's all in the outer envelope. MicroCT and 3D scanning show that the difference between baggy and compact cocoons is in the construction of the outer envelope. The inner envelopes of the two have the same surface area and volume measures. Moreover, the distribution of silk is critical to defining the morphs, as both baggy and compact cocoons contain the same amount of silk.
Larva begins its spinning program.
Larva spinning behavior. This video shows larva spinning outer envelope of a baggy cocoon in spinning arena. It is time-lapse of the first 16 hrs of spinning behavior. It takes 72 hrs to spin the entire cocoon, including outer, intermediate and inner layers.