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.
Leucochloridium paradoxum
The worm in its larval, miracidia stage, travels into the digestive system of a snail to develop into the next stage,
a sporocyst. The sporocyst grows into long tubes to form swollen "broodsacs" filled with tens to hundreds of cercariae. These broodsacs invade the snail's tentacles (preferring the left, when available), causing a brilliant transformation of the tentacles into a swollen, pulsating, colorful display that mimics the appearance of a caterpillar or grub. The broodsacs seem to pulsate in response to light intensity, and in total darkness they do not pulse at all. The infection of the tentacles of the eyes seems to inhibit the perception of light intensity. Whereas uninfected snails seek dark areas to prevent predation, infected snails have a deficit in light detection, and are more likely to become exposed to predators, such as birds. In a study done in Poland, 53% of infected snails stayed in more open places longer, sat on higher vegetation, and stayed in better lit places than uninfected snails. Only 28% of the uninfected snails remained fully exposed for the duration of the observation period. Birds are the definitive hosts where the cercariae develop into adult distomes in the digestive system of the bird. These adult forms sexually reproduce and lay eggs that are released from the host via the bird's excretory system. These droppings are then consumed by snails to complete the life cycle of this parasitic worm.