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
Maru Maru Mori Mori! full-length download to cellphones. Sankei Sports reported that "Maru Maru Mori Mori!" crossed the 250 thousand album sales mark as of 17 July 2011. This makes the group the first Japanese group under 10 years old to exceed 200 thousand sales mark in over 35 years, the last person to do so being Kawahashi Hiroshi with his single "Yamaguchi-sanchi no Tsutomu-kun". On 16 August 2011, Oricon reported that this singles managed to remain in the top 10 list for 12 weeks in a row. Amongst singles released by an artist under 10 years old, "Maru Maru Mori Mori!" now holds