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.
Tent caterpillar
Caterpillars grow rapidly and typically complete their larval development in seven to eight weeks. When fully grown, the caterpillars leave the natal tree and seek protected places on the ground or under the eaves of buildings to spin their cocoons. About two weeks later, they emerge as adults. Shortly after eclosing from the cocoon, the female moth secretes a pheromone which draws males to her. Mating typically occurs in the early evening and the mated female, already fully laden with eggs, typically oviposits the full complement later that same evening. The eggs are placed around the circumference of a branch and covered with a frothy material called spumaline. Spumaline is hydrophilic and prevents the eggs from drying out. It also serves as a protective covering which limits the ability of small wasps to parasitize the eggs. Although the male moth may live for a week or more, the female dies soon after laying her eggs. Thus, the whole of the female's adult life may take place in fewer than 24 hours.