Stages
The silkworm begins as a minuscule egg, which hatches into a caterpillar. The caterpillar grows and then forms a cocoon, from which emerges a moth. The moths mate and then die after the female lays her eggs.
Time Frame
Caterpillars spin their cocoons about six weeks after hatching. If they are allowed to go through metamorphosis, they will emerge as moths two or three weeks later.
Benefits
Luxurious silk fabrics are made from the caterpillars' intact cocoons. The insects inside are killed by boiling the cocoons or heating them in the oven, neither of which harms the fiber.
Significance
Silkworms are so domesticated that they can no longer survive in the wild. Their continued existence depends upon raising by textile producers, laboratories and schoolchildren who are studying them.
Fun Fact
Silkworm eggs are as small as the period at the end of this sentence.