Bombyx mori 300 to about 900 m (1,000 to 3,000 ft) long. The fibers are very fine and lustrous, about 10 μm (0.0004 in) in diameter. About 2,000 to 3,000 cocoons are required to make a pound of silk (0.4 kg). At least 70 million pounds of raw silk are produced each year, requiring nearly 10 billion cocoons. Due to its small size and ease of culture, the silkworm has become a model organism in the study of lepidopteran and arthropod biology. Fundamental findings on pheromones, hormones, brain structures, and physiology have been made with the silkworm. One example of this was
Crustacean larva long rostrum, and a spine on either side of the carapace; the first post-larva closely resembles the adult. Porcelain crabs have two or three larval stages, in which the rostrum and the posterior spine on the carapace are "enormously long". Hermit crabs pass through around four larval stages. The post-larva is known as the "glaucothoe", after a genus named by Henri Milne-Edwards in 1830. The glaucothoe is long in "Pagurus longicarpus", but glaucothoe larvae up to are known, and were once thought to represent animals which had failed to develop correctly. Like the preceding stages, the glaucothoe is symmetrical, and