Silk
Silk moths lay eggs on specially prepared paper. The eggs hatch and the caterpillars (silkworms) are fed fresh mulberry leaves. After about 35 days and 4 moltings, the caterpillars are 10,000 times heavier than when hatched and are ready to begin spinning a cocoon. A straw frame is placed over the tray of caterpillars, and each caterpillar begins spinning a cocoon by moving its head in a pattern. Two glands produce liquid silk and force it through openings in the head called spinnerets. Liquid silk is coated in sericin, a water-soluble protective gum, and solidifies on contact with the air. Within 2–3 days, the caterpillar spins about 1 mile of filament and is completely encased in a cocoon. The silk farmers then heat the cocoons to kill them, leaving some to metamorphose into moths to breed the next generation of caterpillars. Harvested cocoons are then soaked in boiling water to soften the sericin holding the silk fibers together in a cocoon shape. The fibers are then unwound to produce a continuous thread. Since a single thread is too fine and fragile for commercial use, anywhere from three to ten strands are spun together to form a single thread of silk.
Eastern tent caterpillar
The newly hatched caterpillars initiate the construction of a silk tent soon after emerging. They typically aggregate at the tent site throughout their larval stage, expanding the tent each day to accommodate their increasing size. Under field conditions, the caterpillars feed three times each day, just before dawn, at midafternoon, and in the evening after sunset. During each bout of feeding, the caterpillars emerge from the tent, add silk to the structure, move to distant feeding sites "en masse", feed, and then return immediately to the tent where they rest until the next activity period. The exception to this feeding pattern occurs in the last instar, when the caterpillars feed only at night. The insect has six larval instars. At the last stage, the caterpillars disperse and each constructs a cocoon in a protected place. The adult moths, or imagoes, emerge about two weeks later. They are strictly nocturnal and start flying after nightfall, coming to rest within a few hours of dawn. Mating and oviposition typically occur on the day the moths emerge from their cocoons; the females die soon thereafter.